Related
I would like to XML serialize an object that has (among other) a property of type IModelObject (which is an interface).
public class Example
{
public IModelObject Model { get; set; }
}
When I try to serialize an object of this class, I receive the following error:
"Cannot serialize member Example.Model of type Example because it is an interface."
I understand that the problem is that an interface cannot be serialized. However, the concrete Model object type is unknown until runtime.
Replacing the IModelObject interface with an abstract or concrete type and use inheritance with XMLInclude is possible, but seems like an ugly workaround.
Any suggestions?
This is simply an inherent limitation of declarative serialization where type information is not embedded within the output.
On trying to convert <Flibble Foo="10" /> back into
public class Flibble { public object Foo { get; set; } }
How does the serializer know whether it should be an int, a string, a double (or something else)...
To make this work you have several options but if you truly don't know till runtime the easiest way to do this is likely to be using the XmlAttributeOverrides.
Sadly this will only work with base classes, not interfaces. The best you can do there is to ignore the property which isn't sufficient for your needs.
If you really must stay with interfaces you have three real options:
Hide it and deal with it in another property
Ugly, unpleasant boiler plate and much repetition but most consumers of the class will not have to deal with the problem:
[XmlIgnore()]
public object Foo { get; set; }
[XmlElement("Foo")]
[EditorVisibile(EditorVisibility.Advanced)]
public string FooSerialized
{
get { /* code here to convert any type in Foo to string */ }
set { /* code to parse out serialized value and make Foo an instance of the proper type*/ }
}
This is likely to become a maintenance nightmare...
Implement IXmlSerializable
Similar to the first option in that you take full control of things but
Pros
You don't have nasty 'fake' properties hanging around.
you can interact directly with the xml structure adding flexibility/versioning
Cons
you may end up having to re-implement the wheel for all the other properties on the class
Issues of duplication of effort are similar to the first.
Modify your property to use a wrapping type
public sealed class XmlAnything<T> : IXmlSerializable
{
public XmlAnything() {}
public XmlAnything(T t) { this.Value = t;}
public T Value {get; set;}
public void WriteXml (XmlWriter writer)
{
if (Value == null)
{
writer.WriteAttributeString("type", "null");
return;
}
Type type = this.Value.GetType();
XmlSerializer serializer = new XmlSerializer(type);
writer.WriteAttributeString("type", type.AssemblyQualifiedName);
serializer.Serialize(writer, this.Value);
}
public void ReadXml(XmlReader reader)
{
if(!reader.HasAttributes)
throw new FormatException("expected a type attribute!");
string type = reader.GetAttribute("type");
reader.Read(); // consume the value
if (type == "null")
return;// leave T at default value
XmlSerializer serializer = new XmlSerializer(Type.GetType(type));
this.Value = (T)serializer.Deserialize(reader);
reader.ReadEndElement();
}
public XmlSchema GetSchema() { return(null); }
}
Using this would involve something like (in project P):
public namespace P
{
public interface IFoo {}
public class RealFoo : IFoo { public int X; }
public class OtherFoo : IFoo { public double X; }
public class Flibble
{
public XmlAnything<IFoo> Foo;
}
public static void Main(string[] args)
{
var x = new Flibble();
x.Foo = new XmlAnything<IFoo>(new RealFoo());
var s = new XmlSerializer(typeof(Flibble));
var sw = new StringWriter();
s.Serialize(sw, x);
Console.WriteLine(sw);
}
}
which gives you:
<?xml version="1.0" encoding="utf-16"?>
<MainClass
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Foo type="P.RealFoo, P, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
<RealFoo>
<X>0</X>
</RealFoo>
</Foo>
</MainClass>
This is obviously more cumbersome for users of the class though avoids much boiler plate.
A happy medium may be merging the XmlAnything idea into the 'backing' property of the first technique. In this way most of the grunt work is done for you but consumers of the class suffer no impact beyond confusion with introspection.
The solution to this is using reflection with the DataContractSerializer. You don't even have to mark your class with [DataContract] or [DataMember]. It will serialize any object, regardless of whether it has interface type properties (including dictionaries) into xml. Here is a simple extension method that will serialize any object into XML even if it has interfaces (note you could tweak this to run recursively as well).
public static XElement ToXML(this object o)
{
Type t = o.GetType();
Type[] extraTypes = t.GetProperties()
.Where(p => p.PropertyType.IsInterface)
.Select(p => p.GetValue(o, null).GetType())
.ToArray();
DataContractSerializer serializer = new DataContractSerializer(t, extraTypes);
StringWriter sw = new StringWriter();
XmlTextWriter xw = new XmlTextWriter(sw);
serializer.WriteObject(xw, o);
return XElement.Parse(sw.ToString());
}
what the LINQ expression does is it enumerates each property,
returns each property that is an interface,
gets the value of that property (the underlying object),
gets the type of that concrete object
puts it into an array, and adds that to the serializer's list of known types.
Now the serializer knows how about the types it is serializing so it can do its job.
If you know your interface implementors up-front there's a fairly simple hack you can use to get your interface type to serialize without writing any parsing code:
public interface IInterface {}
public class KnownImplementor01 : IInterface {}
public class KnownImplementor02 : IInterface {}
public class KnownImplementor03 : IInterface {}
public class ToSerialize {
[XmlIgnore]
public IInterface InterfaceProperty { get; set; }
[XmlArray("interface")]
[XmlArrayItem("ofTypeKnownImplementor01", typeof(KnownImplementor01))]
[XmlArrayItem("ofTypeKnownImplementor02", typeof(KnownImplementor02))]
[XmlArrayItem("ofTypeKnownImplementor03", typeof(KnownImplementor03))]
public object[] InterfacePropertySerialization {
get { return new[] { InterfaceProperty }; ; }
set { InterfaceProperty = (IInterface)value.Single(); }
}
}
The resulting xml should look something along the lines of
<interface><ofTypeKnownImplementor01><!-- etc... -->
You can use ExtendedXmlSerializer. This serializer support serialization of interface property without any tricks.
var serializer = new ConfigurationContainer().UseOptimizedNamespaces().Create();
var obj = new Example
{
Model = new Model { Name = "name" }
};
var xml = serializer.Serialize(obj);
Your xml will look like:
<?xml version="1.0" encoding="utf-8"?>
<Example xmlns:exs="https://extendedxmlserializer.github.io/v2" xmlns="clr-namespace:ExtendedXmlSerializer.Samples.Simple;assembly=ExtendedXmlSerializer.Samples">
<Model exs:type="Model">
<Name>name</Name>
</Model>
</Example>
ExtendedXmlSerializer support .net 4.5 and .net Core.
Replacing the IModelObject interface with an abstract or concrete type and use inheritance with XMLInclude is possible, but seems like an ugly workaround.
If it is possible to use an abstract base I would recommend that route. It will still be cleaner than using hand-rolled serialization. The only trouble I see with the abstract base is that your still going to need the concrete type? At least that is how I've used it in the past, something like:
public abstract class IHaveSomething
{
public abstract string Something { get; set; }
}
public class MySomething : IHaveSomething
{
string _sometext;
public override string Something
{ get { return _sometext; } set { _sometext = value; } }
}
[XmlRoot("abc")]
public class seriaized
{
[XmlElement("item", typeof(MySomething))]
public IHaveSomething data;
}
Unfortunately there's no simple answer, as the serializer doesn't know what to serialize for an interface. I found a more complete explaination on how to workaround this on MSDN
Unfortuantely for me, I had a case where the class to be serialized had properties that had interfaces as properties as well, so I needed to recursively process each property. Also, some of the interface properties were marked as [XmlIgnore], so I wanted to skip over those. I took ideas that I found on this thread and added some things to it to make it recursive. Only the deserialization code is shown here:
void main()
{
var serializer = GetDataContractSerializer<MyObjectWithCascadingInterfaces>();
using (FileStream stream = new FileStream(xmlPath, FileMode.Open))
{
XmlDictionaryReader reader = XmlDictionaryReader.CreateTextReader(stream, new XmlDictionaryReaderQuotas());
var obj = (MyObjectWithCascadingInterfaces)serializer.ReadObject(reader);
// your code here
}
}
DataContractSerializer GetDataContractSerializer<T>() where T : new()
{
Type[] types = GetTypesForInterfaces<T>();
// Filter out duplicates
Type[] result = types.ToList().Distinct().ToList().ToArray();
var obj = new T();
return new DataContractSerializer(obj.GetType(), types);
}
Type[] GetTypesForInterfaces<T>() where T : new()
{
return GetTypesForInterfaces(typeof(T));
}
Type[] GetTypesForInterfaces(Type T)
{
Type[] result = new Type[0];
var obj = Activator.CreateInstance(T);
// get the type for all interface properties that are not marked as "XmlIgnore"
Type[] types = T.GetProperties()
.Where(p => p.PropertyType.IsInterface &&
!p.GetCustomAttributes(typeof(System.Xml.Serialization.XmlIgnoreAttribute), false).Any())
.Select(p => p.GetValue(obj, null).GetType())
.ToArray();
result = result.ToList().Concat(types.ToList()).ToArray();
// do the same for each of the types identified
foreach (Type t in types)
{
Type[] embeddedTypes = GetTypesForInterfaces(t);
result = result.ToList().Concat(embeddedTypes.ToList()).ToArray();
}
return result;
}
I have found a simpler solution (you don't need the DataContractSerializer), thanks to this blog here:
XML serializing derived types when base type is in another namespace or DLL
But 2 problems can rise in this implementation:
(1) What if DerivedBase is not in the namespace of class Base, or even worse in a project that depends on Base namespace, so Base cannot XMLInclude DerivedBase
(2) What if we only have class Base as a dll ,so again Base cannot XMLInclude DerivedBase
Till now, ...
So the solution to the 2 problems is by using XmlSerializer Constructor (Type, array[]) :
XmlSerializer ser = new XmlSerializer(typeof(A), new Type[]{ typeof(DerivedBase)});
A detailed example is provided here on MSDN:
XmlSerializer Constructor (Type, extraTypesArray[])
It seems to me that for DataContracts or Soap XMLs, you need to check the XmlRoot as mentioned here in this SO question.
A similar answer is here on SO but it isn't marked as one, as it not the OP seems to have considered it already.
in my project, I have a
List<IFormatStyle> FormatStyleTemplates;
containing different Types.
I then use the solution 'XmlAnything' from above, to serialize this list of different types.
The generated xml is beautiful.
[Browsable(false)]
[EditorBrowsable(EditorBrowsableState.Never)]
[XmlArray("FormatStyleTemplates")]
[XmlArrayItem("FormatStyle")]
public XmlAnything<IFormatStyle>[] FormatStyleTemplatesXML
{
get
{
return FormatStyleTemplates.Select(t => new XmlAnything<IFormatStyle>(t)).ToArray();
}
set
{
// read the values back into some new object or whatever
m_FormatStyleTemplates = new FormatStyleProvider(null, true);
value.ForEach(t => m_FormatStyleTemplates.Add(t.Value));
}
}
Is it possible to assign a base class object to a derived class reference with an explicit typecast in C#?.
I have tried it and it creates a run-time error.
No. A reference to a derived class must actually refer to an instance of the derived class (or null). Otherwise how would you expect it to behave?
For example:
object o = new object();
string s = (string) o;
int i = s.Length; // What can this sensibly do?
If you want to be able to convert an instance of the base type to the derived type, I suggest you write a method to create an appropriate derived type instance. Or look at your inheritance tree again and try to redesign so that you don't need to do this in the first place.
No, that's not possible since assigning it to a derived class reference would be like saying "Base class is a fully capable substitute for derived class, it can do everything the derived class can do", which is not true since derived classes in general offer more functionality than their base class (at least, that's the idea behind inheritance).
You could write a constructor in the derived class taking a base class object as parameter, copying the values.
Something like this:
public class Base {
public int Data;
public void DoStuff() {
// Do stuff with data
}
}
public class Derived : Base {
public int OtherData;
public Derived(Base b) {
this.Data = b.Data;
OtherData = 0; // default value
}
public void DoOtherStuff() {
// Do some other stuff
}
}
In that case you would copy the base object and get a fully functional derived class object with default values for derived members. This way you can also avoid the problem pointed out by Jon Skeet:
Base b = new Base();//base class
Derived d = new Derived();//derived class
b.DoStuff(); // OK
d.DoStuff(); // Also OK
b.DoOtherStuff(); // Won't work!
d.DoOtherStuff(); // OK
d = new Derived(b); // Copy construct a Derived with values of b
d.DoOtherStuff(); // Now works!
Solution with JsonConvert (instead of typecast)
Today i faced the same issue and i found a simple and quick solution to the problem using JsonConvert.
var base = new BaseClass();
var json = JsonConvert.SerializeObject(base);
DerivedClass derived = JsonConvert.DeserializeObject<DerivedClass>(json);
I had this problem and solved it by adding a method that takes a type parameter and converts the current object into that type.
public TA As<TA>() where TA : Base
{
var type = typeof (TA);
var instance = Activator.CreateInstance(type);
PropertyInfo[] properties = type.GetProperties();
foreach (var property in properties)
{
property.SetValue(instance, property.GetValue(this, null), null);
}
return (TA)instance;
}
That means that you can use it in you code like this:
var base = new Base();
base.Data = 1;
var derived = base.As<Derived>();
Console.Write(derived.Data); // Would output 1
As many others have answered, No.
I use the following code on those unfortunate occasions when I need to use a base type as a derived type. Yes it is a violation of the Liskov Substitution Principle (LSP) and yes most of the time we favor composition over inheritance. Props to Markus Knappen Johansson whose original answer this is based upon.
This code in the base class:
public T As<T>()
{
var type = typeof(T);
var instance = Activator.CreateInstance(type);
if (type.BaseType != null)
{
var properties = type.BaseType.GetProperties();
foreach (var property in properties)
if (property.CanWrite)
property.SetValue(instance, property.GetValue(this, null), null);
}
return (T) instance;
}
Allows:
derivedObject = baseObect.As<derivedType>()
Since it uses reflection, it is "expensive". Use accordingly.
No it is not possible, hence your runtime error.
But you can assign an instance of a derived class to a variable of base class type.
As everyone here said, that's not possible directly.
The method I prefer and is rather clean, is to use an Object Mapper like AutoMapper.
It will do the task of copying properties from one instance to another (Not necessarily the same type) automatically.
In c# 9.0 you can try to use records for this. They have default copy constructor that copy all fields - no need to use reflection / constructor with all fields.
public record BaseR
{
public string Prop1 { get; set; }
}
public record DerivedR : BaseR
{
public DerivedR(BaseR baseR) : base(baseR) { }
public string Prop2 { get; set; }
}
var baseR = new BaseR { Prop1 = "base prob" };
var derivedR = new DerivedR(baseR) { Prop2 = "new prop" };
Not in the Traditional Sense... Convert to Json, then to your object, and boom, done! Jesse above had the answer posted first, but didn't use these extension methods which make the process so much easier. Create a couple of extension methods:
public static string ConvertToJson<T>(this T obj)
{
return JsonConvert.SerializeObject(obj);
}
public static T ConvertToObject<T>(this string json)
{
if (string.IsNullOrEmpty(json))
{
return Activator.CreateInstance<T>();
}
return JsonConvert.DeserializeObject<T>(json);
}
Put them in your toolbox forever, then you can always do this:
var derivedClass = baseClass.ConvertToJson().ConvertToObject<derivedClass>();
Ah, the power of JSON.
There are a couple of gotchas with this approach: We really are creating a new object, not casting, which may or may not matter. Private fields will not be transferred, constructors with parameters won't be called, etc. It is possible that some child json won't be assigned. Streams are not innately handled by JsonConvert. However, if our class doesn't rely on private fields and constructors, this is a very effective method of moving data from class to class without mapping and calling constructors, which is the main reason why we want to cast in the first place.
Expanding on #ybo's answer - it isn't possible because the instance you have of the base class isn't actually an instance of the derived class. It only knows about the members of the base class, and doesn't know anything about those of the derived class.
The reason that you can cast an instance of the derived class to an instance of the base class is because the derived class actually already is an instance of the base class, since it has those members already. The opposite cannot be said.
You can cast a variable that is typed as the base-class to the type of a derived class; however, by necessity this will do a runtime check, to see if the actual object involved is of the correct type.
Once created, the type of an object cannot be changed (not least, it might not be the same size). You can, however, convert an instance, creating a new instance of the second type - but you need to write the conversion code manually.
You have to use an object cloner/copier that will assign all the properties one by one.
Doing this by hand is inefficient and not future-proof. But serializing & deserializing to JSON and back is not the best solution, it is slow and very memory inefficient.
However, using AutoMapper is fast. PropMapper is even faster.
PS. Disclosure: I am a contributor at PropMapper open source project.
No, it is not possible.
Consider a scenario where an ACBus is a derived class of base class Bus. ACBus has features like TurnOnAC and TurnOffAC which operate on a field named ACState. TurnOnAC sets ACState to on and TurnOffAC sets ACState to off. If you try to use TurnOnAC and TurnOffAC features on Bus, it makes no sense.
class Program
{
static void Main(string[] args)
{
a a1 = new b();
a1.print();
}
}
class a
{
public a()
{
Console.WriteLine("base class object initiated");
}
public void print()
{
Console.WriteLine("base");
}
}
class b:a
{
public b()
{
Console.WriteLine("child class object");
}
public void print1()
{
Console.WriteLine("derived");
}
}
}
when we create a child class object,the base class object is auto initiated so base class reference variable can point to child class object.
but not vice versa because a child class reference variable can not point to base class object because no child class object is created.
and also notice that base class reference variable can only call base class member.
There actually IS a way to do this. Think about how you might use Newtonsoft JSON to deserialize an object from json. It will (or at least can) ignore missing elements and populate all the elements that it does know about.
So here's how I did it. A small code sample will follow my explanation.
Create an instance of your object from the base class and populate it accordingly.
Using the "jsonconvert" class of Newtonsoft json, serialize that object into a json string.
Now create your sub class object by deserializing with the json string created in step 2. This will create an instance of your sub class with all the properties of the base class.
This works like a charm! So.. when is this useful? Some people asked when this would make sense and suggested changing the OP's schema to accommodate the fact that you can't natively do this with class inheritance (in .Net).
In my case, I have a settings class that contains all the "base" settings for a service. Specific services have more options and those come from a different DB table, so those classes inherit the base class. They all have a different set of options. So when retrieving the data for a service, it's much easier to FIRST populate the values using an instance of the base object. One method to do this with a single DB query. Right after that, I create the sub class object using the method outlined above. I then make a second query and populate all the dynamic values on the sub class object.
The final output is a derived class with all the options set. Repeating this for additional new sub classes takes just a few lines of code. It's simple, and it uses a very tried and tested package (Newtonsoft) to make the magic work.
This example code is vb.Net, but you can easily convert to c#.
' First, create the base settings object.
Dim basePMSettngs As gtmaPayMethodSettings = gtmaPayments.getBasePayMethodSetting(payTypeId, account_id)
Dim basePMSettingsJson As String = JsonConvert.SerializeObject(basePMSettngs, Formatting.Indented)
' Create a pmSettings object of this specific type of payment and inherit from the base class object
Dim pmSettings As gtmaPayMethodAimACHSettings = JsonConvert.DeserializeObject(Of gtmaPayMethodAimACHSettings)(basePMSettingsJson)
You can use an Extention:
public static void CopyOnlyEqualProperties<T>(this T objDest, object objSource) where T : class
{
foreach (PropertyInfo propInfo in typeof(T).GetProperties())
if (objSource.GetType().GetProperties().Any(z => z.Name == propInfo.Name && z.GetType() == propInfo.GetType()))
propInfo.SetValue(objDest, objSource.GetType().GetProperties().First(z => z.Name == propInfo.Name && z.GetType() == propInfo.GetType()).GetValue(objSource));
}
In Code:
public class BaseClass
{
public string test{ get; set;}
}
public Derived : BaseClass
{
//Some properies
}
public void CopyProps()
{
BaseClass baseCl =new BaseClass();
baseCl.test="Hello";
Derived drv=new Derived();
drv.CopyOnlyEqualProperties(baseCl);
//Should return Hello to the console now in derived class.
Console.WriteLine(drv.test);
}
Might not be relevent, but I was able to run code on a derived object given its base. It's definitely more hacky than I'd like, but it works:
public static T Cast<T>(object obj)
{
return (T)obj;
}
...
//Invoke parent object's json function
MethodInfo castMethod = this.GetType().GetMethod("Cast").MakeGenericMethod(baseObj.GetType());
object castedObject = castMethod.Invoke(null, new object[] { baseObj });
MethodInfo jsonMethod = baseObj.GetType ().GetMethod ("ToJSON");
return (string)jsonMethod.Invoke (castedObject,null);
You can do this using generic.
public class BaseClass
{
public int A { get; set; }
public int B { get; set; }
private T ConvertTo<T>() where T : BaseClass, new()
{
return new T
{
A = A,
B = B
}
}
public DerivedClass1 ConvertToDerivedClass1()
{
return ConvertTo<DerivedClass1>();
}
public DerivedClass2 ConvertToDerivedClass2()
{
return ConvertTo<DerivedClass2>();
}
}
public class DerivedClass1 : BaseClass
{
public int C { get; set; }
}
public class DerivedClass2 : BaseClass
{
public int D { get; set; }
}
You get three benefits using this approach.
You are not duplicating the code
You are not using reflection (which is slow)
All of your conversions are in one place
I know this is old but I've used this successfully for quite a while.
private void PopulateDerivedFromBase<TB,TD>(TB baseclass,TD derivedclass)
{
//get our baseclass properties
var bprops = baseclass.GetType().GetProperties();
foreach (var bprop in bprops)
{
//get the corresponding property in the derived class
var dprop = derivedclass.GetType().GetProperty(bprop.Name);
//if the derived property exists and it's writable, set the value
if (dprop != null && dprop.CanWrite)
dprop.SetValue(derivedclass,bprop.GetValue(baseclass, null),null);
}
}
I combined some portions of the previous answers (thanks to those authors) and put together a simple static class with two methods that we're using.
Yes, it's simple, no it doesn't cover all scenarios, yes it could be expanded and made better, no it's not perfect, yes it could possibly be made more efficient, no it's not the greatest thing since sliced bread, yes there are full-on robust nuget package object mappers out there that are way better for heavy use, etc etc, yada yada - but it works for our basic needs though :)
And of course it will try to map values from any object to any object, derived or not (only the public properties that are named the same of course - ignores the rest).
USAGE:
SesameStreetCharacter puppet = new SesameStreetCharacter() { Name = "Elmo", Age = 5 };
// creates new object of type "RealPerson" and assigns any matching property
// values from the puppet object
// (this method requires that "RealPerson" have a parameterless constructor )
RealPerson person = ObjectMapper.MapToNewObject<RealPerson>(puppet);
// OR
// create the person object on our own
// (so RealPerson can have any constructor type that it wants)
SesameStreetCharacter puppet = new SesameStreetCharacter() { Name = "Elmo", Age = 5 };
RealPerson person = new RealPerson("tall") {Name = "Steve"};
// maps and overwrites any matching property values from
// the puppet object to the person object so now our person's age will get set to 5 and
// the name "Steve" will get overwritten with "Elmo" in this example
ObjectMapper.MapToExistingObject(puppet, person);
STATIC UTILITY CLASS:
public static class ObjectMapper
{
// the target object is created on the fly and the target type
// must have a parameterless constructor (either compiler-generated or explicit)
public static Ttarget MapToNewObject<Ttarget>(object sourceobject) where Ttarget : new()
{
// create an instance of the target class
Ttarget targetobject = (Ttarget)Activator.CreateInstance(typeof(Ttarget));
// map the source properties to the target object
MapToExistingObject(sourceobject, targetobject);
return targetobject;
}
// the target object is created beforehand and passed in
public static void MapToExistingObject(object sourceobject, object targetobject)
{
// get the list of properties available in source class
var sourceproperties = sourceobject.GetType().GetProperties().ToList();
// loop through source object properties
sourceproperties.ForEach(sourceproperty => {
var targetProp = targetobject.GetType().GetProperty(sourceproperty.Name);
// check whether that property is present in target class and is writeable
if (targetProp != null && targetProp.CanWrite)
{
// if present get the value and map it
var value = sourceobject.GetType().GetProperty(sourceproperty.Name).GetValue(sourceobject, null);
targetobject.GetType().GetProperty(sourceproperty.Name).SetValue(targetobject, value, null);
}
});
}
}
You can use a copy constructor that immediately invokes the instance constructor, or if your instance constructor does more than assignments have the copy constructor assign the incoming values to the instance.
class Person
{
// Copy constructor
public Person(Person previousPerson)
{
Name = previousPerson.Name;
Age = previousPerson.Age;
}
// Copy constructor calls the instance constructor.
public Person(Person previousPerson)
: this(previousPerson.Name, previousPerson.Age)
{
}
// Instance constructor.
public Person(string name, int age)
{
Name = name;
Age = age;
}
public int Age { get; set; }
public string Name { get; set; }
}
Referenced the Microsoft C# Documentation under Constructor for this example having had this issue in the past.
With regarding #MarkusKnappenJohansson answer and below comments we can change his code extending extension function :) so it may update an existing deriving class instance via this code :
public static TDerived As<TDerived>(this Base baseInstance, TDerived updateDerivedInstance = null) where TDerived : Base, new()
{
Type baseType = typeof(Base);
Type derivedType = typeof(TDerived);
PropertyInfo[] properties = baseType.GetProperties();
object instanceDerived = null;
if (updateDerivedInstance == null)
{
instanceDerived = Activator.CreateInstance(derivedType);
}
else
{
instanceDerived = (object)(updateDerivedInstance);
}
foreach (PropertyInfo property in properties)
{
if (property.CanWrite)
{
property.SetValue(instanceDerived, property.GetValue(baseInstance, null), null);
}
}
return (TDerived)instanceDerived;
}
Usage for getting new derived Instance is var base = new Base(); base.Data = 1; var derived = base.As<Derived>(); Console.Write(derived.Data); // Would output 1
Usage for updating existing derived Instance is var derived = new Derived(); var base = new Base(); base.Data = 1; var derivedUpdated = base.As<Derived>(derived); Console.Write(derivedUpdated.Data); // Would output 1
Another solution is to add extension method like so:
public static void CopyProperties(this object destinationObject, object sourceObject, bool overwriteAll = true)
{
try
{
if (sourceObject != null)
{
PropertyInfo[] sourceProps = sourceObject.GetType().GetProperties();
List<string> sourcePropNames = sourceProps.Select(p => p.Name).ToList();
foreach (PropertyInfo pi in destinationObject.GetType().GetProperties())
{
if (sourcePropNames.Contains(pi.Name))
{
PropertyInfo sourceProp = sourceProps.First(srcProp => srcProp.Name == pi.Name);
if (sourceProp.PropertyType == pi.PropertyType)
if (overwriteAll || pi.GetValue(destinationObject, null) == null)
{
pi.SetValue(destinationObject, sourceProp.GetValue(sourceObject, null), null);
}
}
}
}
}
catch (ApplicationException ex)
{
throw;
}
}
then have a constructor in each derived class that accepts base class:
public class DerivedClass: BaseClass
{
public DerivedClass(BaseClass baseModel)
{
this.CopyProperties(baseModel);
}
}
It will also optionally overwrite destination properties if already set (not null) or not.
Is it possible to assign a base class object to a derived class reference with an explicit typecast in C#?.
Not only explicit, but also implicit conversions are possible.
C# language doesn't permit such conversion operators, but you can still write them using pure C# and they work. Note that the class which defines the implicit conversion operator (Derived) and the class which uses the operator (Program) must be defined in separate assemblies (e.g. the Derived class is in a library.dll which is referenced by program.exe containing the Program class).
//In library.dll:
public class Base { }
public class Derived {
[System.Runtime.CompilerServices.SpecialName]
public static Derived op_Implicit(Base a) {
return new Derived(a); //Write some Base -> Derived conversion code here
}
[System.Runtime.CompilerServices.SpecialName]
public static Derived op_Explicit(Base a) {
return new Derived(a); //Write some Base -> Derived conversion code here
}
}
//In program.exe:
class Program {
static void Main(string[] args) {
Derived z = new Base(); //Visual Studio can show squiggles here, but it compiles just fine.
}
}
When you reference the library using the Project Reference in Visual Studio, VS shows squiggles when you use the implicit conversion, but it compiles just fine. If you just reference the library.dll, there are no squiggles.
How about:
public static T As<T>(this object obj)
{
return JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(obj));
}
Best way to add all base properties to derived item is use reflection in costructor. Try this code, without creating methods or instances.
public Derived(Base item) :base()
{
Type type = item.GetType();
System.Reflection.PropertyInfo[] properties = type.GetProperties();
foreach (var property in properties)
{
try
{
property.SetValue(this, property.GetValue(item, null), null);
}
catch (Exception) { }
}
}
I disagree that it is not possible. You can do it like this:
public class Auto
{
public string Make {get; set;}
public string Model {get; set;}
}
public class Sedan : Auto
{
public int NumberOfDoors {get; set;}
}
public static T ConvertAuto<T>(Sedan sedan) where T : class
{
object auto = sedan;
return (T)loc;
}
Usage:
var sedan = new Sedan();
sedan.NumberOfDoors = 4;
var auto = ConvertAuto<Auto>(sedan);
This is how I solved this for fields. You can do the same iteration through properties if you want. You may want to do some checks for null etc. but this is the idea.
public static DerivedClass ConvertFromBaseToDerived<BaseClass, DerivedClass>(BaseClass baseClass)
where BaseClass : class, new()
where DerivedClass : class, BaseClass, new()
{
DerivedClass derived = (DerivedClass)Activator.CreateInstance(typeof(DerivedClass));
derived.GetType().GetFields().ToList().ForEach(field =>
{
var base_ = baseClass.GetType().GetField(field.Name).GetValue(baseClass);
field.SetValue(derived, base_);
});
return derived;
}
You can just serialize the base object to JSON and then deserialize it to the derived object.
No, see this question which I asked - Upcasting in .NET using generics
The best way is to make a default constructor on the class, construct and then call an Initialise method
I would like to XML serialize an object that has (among other) a property of type IModelObject (which is an interface).
public class Example
{
public IModelObject Model { get; set; }
}
When I try to serialize an object of this class, I receive the following error:
"Cannot serialize member Example.Model of type Example because it is an interface."
I understand that the problem is that an interface cannot be serialized. However, the concrete Model object type is unknown until runtime.
Replacing the IModelObject interface with an abstract or concrete type and use inheritance with XMLInclude is possible, but seems like an ugly workaround.
Any suggestions?
This is simply an inherent limitation of declarative serialization where type information is not embedded within the output.
On trying to convert <Flibble Foo="10" /> back into
public class Flibble { public object Foo { get; set; } }
How does the serializer know whether it should be an int, a string, a double (or something else)...
To make this work you have several options but if you truly don't know till runtime the easiest way to do this is likely to be using the XmlAttributeOverrides.
Sadly this will only work with base classes, not interfaces. The best you can do there is to ignore the property which isn't sufficient for your needs.
If you really must stay with interfaces you have three real options:
Hide it and deal with it in another property
Ugly, unpleasant boiler plate and much repetition but most consumers of the class will not have to deal with the problem:
[XmlIgnore()]
public object Foo { get; set; }
[XmlElement("Foo")]
[EditorVisibile(EditorVisibility.Advanced)]
public string FooSerialized
{
get { /* code here to convert any type in Foo to string */ }
set { /* code to parse out serialized value and make Foo an instance of the proper type*/ }
}
This is likely to become a maintenance nightmare...
Implement IXmlSerializable
Similar to the first option in that you take full control of things but
Pros
You don't have nasty 'fake' properties hanging around.
you can interact directly with the xml structure adding flexibility/versioning
Cons
you may end up having to re-implement the wheel for all the other properties on the class
Issues of duplication of effort are similar to the first.
Modify your property to use a wrapping type
public sealed class XmlAnything<T> : IXmlSerializable
{
public XmlAnything() {}
public XmlAnything(T t) { this.Value = t;}
public T Value {get; set;}
public void WriteXml (XmlWriter writer)
{
if (Value == null)
{
writer.WriteAttributeString("type", "null");
return;
}
Type type = this.Value.GetType();
XmlSerializer serializer = new XmlSerializer(type);
writer.WriteAttributeString("type", type.AssemblyQualifiedName);
serializer.Serialize(writer, this.Value);
}
public void ReadXml(XmlReader reader)
{
if(!reader.HasAttributes)
throw new FormatException("expected a type attribute!");
string type = reader.GetAttribute("type");
reader.Read(); // consume the value
if (type == "null")
return;// leave T at default value
XmlSerializer serializer = new XmlSerializer(Type.GetType(type));
this.Value = (T)serializer.Deserialize(reader);
reader.ReadEndElement();
}
public XmlSchema GetSchema() { return(null); }
}
Using this would involve something like (in project P):
public namespace P
{
public interface IFoo {}
public class RealFoo : IFoo { public int X; }
public class OtherFoo : IFoo { public double X; }
public class Flibble
{
public XmlAnything<IFoo> Foo;
}
public static void Main(string[] args)
{
var x = new Flibble();
x.Foo = new XmlAnything<IFoo>(new RealFoo());
var s = new XmlSerializer(typeof(Flibble));
var sw = new StringWriter();
s.Serialize(sw, x);
Console.WriteLine(sw);
}
}
which gives you:
<?xml version="1.0" encoding="utf-16"?>
<MainClass
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Foo type="P.RealFoo, P, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
<RealFoo>
<X>0</X>
</RealFoo>
</Foo>
</MainClass>
This is obviously more cumbersome for users of the class though avoids much boiler plate.
A happy medium may be merging the XmlAnything idea into the 'backing' property of the first technique. In this way most of the grunt work is done for you but consumers of the class suffer no impact beyond confusion with introspection.
The solution to this is using reflection with the DataContractSerializer. You don't even have to mark your class with [DataContract] or [DataMember]. It will serialize any object, regardless of whether it has interface type properties (including dictionaries) into xml. Here is a simple extension method that will serialize any object into XML even if it has interfaces (note you could tweak this to run recursively as well).
public static XElement ToXML(this object o)
{
Type t = o.GetType();
Type[] extraTypes = t.GetProperties()
.Where(p => p.PropertyType.IsInterface)
.Select(p => p.GetValue(o, null).GetType())
.ToArray();
DataContractSerializer serializer = new DataContractSerializer(t, extraTypes);
StringWriter sw = new StringWriter();
XmlTextWriter xw = new XmlTextWriter(sw);
serializer.WriteObject(xw, o);
return XElement.Parse(sw.ToString());
}
what the LINQ expression does is it enumerates each property,
returns each property that is an interface,
gets the value of that property (the underlying object),
gets the type of that concrete object
puts it into an array, and adds that to the serializer's list of known types.
Now the serializer knows how about the types it is serializing so it can do its job.
If you know your interface implementors up-front there's a fairly simple hack you can use to get your interface type to serialize without writing any parsing code:
public interface IInterface {}
public class KnownImplementor01 : IInterface {}
public class KnownImplementor02 : IInterface {}
public class KnownImplementor03 : IInterface {}
public class ToSerialize {
[XmlIgnore]
public IInterface InterfaceProperty { get; set; }
[XmlArray("interface")]
[XmlArrayItem("ofTypeKnownImplementor01", typeof(KnownImplementor01))]
[XmlArrayItem("ofTypeKnownImplementor02", typeof(KnownImplementor02))]
[XmlArrayItem("ofTypeKnownImplementor03", typeof(KnownImplementor03))]
public object[] InterfacePropertySerialization {
get { return new[] { InterfaceProperty }; ; }
set { InterfaceProperty = (IInterface)value.Single(); }
}
}
The resulting xml should look something along the lines of
<interface><ofTypeKnownImplementor01><!-- etc... -->
You can use ExtendedXmlSerializer. This serializer support serialization of interface property without any tricks.
var serializer = new ConfigurationContainer().UseOptimizedNamespaces().Create();
var obj = new Example
{
Model = new Model { Name = "name" }
};
var xml = serializer.Serialize(obj);
Your xml will look like:
<?xml version="1.0" encoding="utf-8"?>
<Example xmlns:exs="https://extendedxmlserializer.github.io/v2" xmlns="clr-namespace:ExtendedXmlSerializer.Samples.Simple;assembly=ExtendedXmlSerializer.Samples">
<Model exs:type="Model">
<Name>name</Name>
</Model>
</Example>
ExtendedXmlSerializer support .net 4.5 and .net Core.
Replacing the IModelObject interface with an abstract or concrete type and use inheritance with XMLInclude is possible, but seems like an ugly workaround.
If it is possible to use an abstract base I would recommend that route. It will still be cleaner than using hand-rolled serialization. The only trouble I see with the abstract base is that your still going to need the concrete type? At least that is how I've used it in the past, something like:
public abstract class IHaveSomething
{
public abstract string Something { get; set; }
}
public class MySomething : IHaveSomething
{
string _sometext;
public override string Something
{ get { return _sometext; } set { _sometext = value; } }
}
[XmlRoot("abc")]
public class seriaized
{
[XmlElement("item", typeof(MySomething))]
public IHaveSomething data;
}
Unfortunately there's no simple answer, as the serializer doesn't know what to serialize for an interface. I found a more complete explaination on how to workaround this on MSDN
Unfortuantely for me, I had a case where the class to be serialized had properties that had interfaces as properties as well, so I needed to recursively process each property. Also, some of the interface properties were marked as [XmlIgnore], so I wanted to skip over those. I took ideas that I found on this thread and added some things to it to make it recursive. Only the deserialization code is shown here:
void main()
{
var serializer = GetDataContractSerializer<MyObjectWithCascadingInterfaces>();
using (FileStream stream = new FileStream(xmlPath, FileMode.Open))
{
XmlDictionaryReader reader = XmlDictionaryReader.CreateTextReader(stream, new XmlDictionaryReaderQuotas());
var obj = (MyObjectWithCascadingInterfaces)serializer.ReadObject(reader);
// your code here
}
}
DataContractSerializer GetDataContractSerializer<T>() where T : new()
{
Type[] types = GetTypesForInterfaces<T>();
// Filter out duplicates
Type[] result = types.ToList().Distinct().ToList().ToArray();
var obj = new T();
return new DataContractSerializer(obj.GetType(), types);
}
Type[] GetTypesForInterfaces<T>() where T : new()
{
return GetTypesForInterfaces(typeof(T));
}
Type[] GetTypesForInterfaces(Type T)
{
Type[] result = new Type[0];
var obj = Activator.CreateInstance(T);
// get the type for all interface properties that are not marked as "XmlIgnore"
Type[] types = T.GetProperties()
.Where(p => p.PropertyType.IsInterface &&
!p.GetCustomAttributes(typeof(System.Xml.Serialization.XmlIgnoreAttribute), false).Any())
.Select(p => p.GetValue(obj, null).GetType())
.ToArray();
result = result.ToList().Concat(types.ToList()).ToArray();
// do the same for each of the types identified
foreach (Type t in types)
{
Type[] embeddedTypes = GetTypesForInterfaces(t);
result = result.ToList().Concat(embeddedTypes.ToList()).ToArray();
}
return result;
}
I have found a simpler solution (you don't need the DataContractSerializer), thanks to this blog here:
XML serializing derived types when base type is in another namespace or DLL
But 2 problems can rise in this implementation:
(1) What if DerivedBase is not in the namespace of class Base, or even worse in a project that depends on Base namespace, so Base cannot XMLInclude DerivedBase
(2) What if we only have class Base as a dll ,so again Base cannot XMLInclude DerivedBase
Till now, ...
So the solution to the 2 problems is by using XmlSerializer Constructor (Type, array[]) :
XmlSerializer ser = new XmlSerializer(typeof(A), new Type[]{ typeof(DerivedBase)});
A detailed example is provided here on MSDN:
XmlSerializer Constructor (Type, extraTypesArray[])
It seems to me that for DataContracts or Soap XMLs, you need to check the XmlRoot as mentioned here in this SO question.
A similar answer is here on SO but it isn't marked as one, as it not the OP seems to have considered it already.
in my project, I have a
List<IFormatStyle> FormatStyleTemplates;
containing different Types.
I then use the solution 'XmlAnything' from above, to serialize this list of different types.
The generated xml is beautiful.
[Browsable(false)]
[EditorBrowsable(EditorBrowsableState.Never)]
[XmlArray("FormatStyleTemplates")]
[XmlArrayItem("FormatStyle")]
public XmlAnything<IFormatStyle>[] FormatStyleTemplatesXML
{
get
{
return FormatStyleTemplates.Select(t => new XmlAnything<IFormatStyle>(t)).ToArray();
}
set
{
// read the values back into some new object or whatever
m_FormatStyleTemplates = new FormatStyleProvider(null, true);
value.ForEach(t => m_FormatStyleTemplates.Add(t.Value));
}
}
I work an an automation team designing tests for electronic components. One thing our framework sorely needs is a single source point for our driver objects for the various pieces of test equipment at a workbench (right now, driver object creation is very wild-west).
Basically, the idea would be there would be one object, constructed based on a configuration file(s), which is the single place all other test code looks to to get the driver objects, based on a name string. I'll call it a "DriverSource" here.
The problem is, these drivers do not present similar interfaces at all. One might be a power supply (with methods like "SetVoltage" and "SetCurrentLimit"), while another might be a digital multimeter (with methods like "ReadVoltage" or "ReadCurrent").
The best solution I've come up with is to have a method with the following declaration:
public object GetDriver(string name);
Then, the test code using my "DriverSource" object would call that method, and then cast the System.Object to the correct driver type (or more accurately, the correct driver interface, like IPowerSupply).
I think casting like that is acceptable because whatever test code is about to use this driver had better know what the interface is. But I was hoping to get some input on whether or not this is an anti-pattern waiting to bite me. Any better pattern for solving this issue would also be greatly appreciated.
A final note: I think this is obvious, but performance is essentially a non-issue for this problem. Fetching the drivers is something will happen less than 100 times in a test run that can last hours.
If you already know the type and you're going to cast to an interface or class anyway, a better approach would be to hand the method call a type parameter.
public T GetDriver<T>(string name);
You can then use a Factory pattern to return you an object of the appropriate type from the method.
public T GetDriver<T>(string name)
{
switch(typeof(T).Name)
{
case "Foo":
// Construct and return a Foo object
case "Bar":
// Construct and return a Bar object
case "Baz":
// Construct and return a Baz object
default:
return default(T);
}
}
Usage:
var driver = GetDriver<Foo>(someString); // Returns a Foo object
If you really want to make this generic, I would use a factory pattern.
Lets start off by identifying the type structure:
public interface IDriver
{
}
public interface IPowerSupply : IDriver
{
void SetVoltage();
void SetCurrent();
}
public interface IMultimeter : IDriver
{
double MeasureVoltage();
}
Which you can add to or remove from as needed. Now we need a way for the factory to auto-discover the correct types and provide the configuration information to it. So lets create a custom attribute:
public class DriverHandlerAttribute : Attribute
{
public Type DriverType { get; set; }
public string ConfigurationName { get; set; }
}
And then we need a place to store configuration data. This type can contain whatever you want, like a dictionary of keys/values that are loaded from configuration files:
public class Configuration
{
public string DriverName { get; set; }
public string OtherSetting { get; set; }
}
Finally we can create a driver. Lets create an IPowerSupply:
[DriverHandler(DriverType = typeof(IPowerSupply), ConfigurationName="BaseSupply")]
public class BasePowerSupply : IPowerSupply
{
public BasePowerSupply(Configuration config) { /* ... */ }
public void SetVoltage() { /* ... */ }
public void SetCurrent() { /* ... */ }
}
The important part is that it is decorated with the attribute and that it has a constructor (although I created the factory so that it can use default constructors too):
public static class DriverFactory
{
public static IDriver Create(Configuration config)
{
Type driverType = GetTypeForDriver(config.DriverName);
if (driverType == null) return null;
if (driverType.GetConstructor(new[] { typeof(Configuration) }) != null)
return Activator.CreateInstance(driverType, config) as IDriver;
else
return Activator.CreateInstance(driverType) as IDriver;
}
public static T Create<T>(Configuration config) where T : IDriver
{
return (T)Create(config);
}
private static Type GetTypeForDriver(string driverName)
{
var type = (from t in Assembly.GetExecutingAssembly().GetTypes()
let attrib = t.GetCustomAttribute<DriverHandlerAttribute>()
where attrib != null && attrib.ConfigurationName == driverName
select t).FirstOrDefault();
return type;
}
}
So to use this, you would read in the configuration data (loaded from XML, read from a service, files, etc). You can then create the driver like:
var driver = DriverFactory.Create(configuration);
Or if you are using the generic method and you know the configuration is for a power supply, you can call:
var driver = DriverFactory.Create<IPowerSupply>(configuration);
And when you run your tests, you can verify that you get the right data back, for example, in your test method:
Assert.IsTrue(driver is IPowerSupply);
Assert.IsTrue(driver is BaseSupply);
Assert.DoesWhatever(((IPowerSupply)driver).SetVoltage());
And so-on and so-forth.
I would go with this code:
public T GetDriver<T>(string name)
{
return ((Func<string, T>)_factories[typeof(T)])(name);
}
The _factories object looks like this:
private Dictionary<Type, Delegate> _factories = new Dictionary<Type, Delegate>()
{
{ typeof(Foo), (Delegate)(Func<string, Foo>)(s => new Foo(s)) },
{ typeof(Bar), (Delegate)(Func<string, Bar>)(s => new Bar()) },
{ typeof(Baz), (Delegate)(Func<string, Baz>)(s => new Baz()) },
};
Basically the _factories dictionary contains all of the code to create each object type based on string parameter passed in. Note that in my example above the Foo class takes s as a constructor parameter.
The dictionary can also then be modified at run-time to suite your needs without needing to recompile code.
I would even go one step further. If you define this factory class:
public class Factory
{
private Dictionary<Type, Delegate> _factories = new Dictionary<Type, Delegate>();
public T Build<T>(string name)
{
return ((Func<string, T>)_factories[typeof(T)])(name);
}
public void Define<T>(Func<string, T> create)
{
_factories.Add(typeof(T), create);
}
}
You can then write this code:
var drivers = new Factory();
drivers.Define(s => new Foo(s));
drivers.Define(s => new Bar());
drivers.Define(s => new Baz());
var driver = drivers.Build<Foo>("foo");
I like that even better. It's strongly-typed and easily customized at run-time.
I need to make a copy of a MyGame class and use it in my simulation for game trials before I select a move to play.
For example :
public class MyGame
{
private int Start;
private Board board;
//Constructor
public void Play()
{
//play game
}
public object Clone()
{
}
}
public class Board
{
private int Count;
//Constructor
//Some methods and properties
public object Clone()
{
}
}
Writing code for the method Clone() I have tried
MemberwiseClone()
(Board) this.MemberwiseClone()
Board b = (Board) this.Board
I have read alot of articles and forums about this topic. The answer most people
use is Deep cloning objects in C#, I tried samples with respect to my project but I still
get my simulation modifying the original object (MyGame Class) and not the copy.
Here I have an example for a deep copy, which deeply copies all reference type objects that are used with a copy constructor:
public sealed class MyGame
{
private int start;
private Board board;
public MyGame(MyGame orig)
{
// value types - like integers - can easily be
// reused
this.start = orig.start;
// reference types must be clones seperately, you
// must not use orig.board directly here
this.board = new Board(orig.board);
}
}
public sealed class Board
{
private int count;
public Board(Board orig)
{
// here we have a value type again
this.count = orig.count;
// here we have no reference types. if we did
// we'd have to clone them too, as above
}
}
I think your copy might be somehow shallow and re-use some references (like for instance this.board = orig.board instead of creating a new board). This is a guess though, as I can't see your cloning implementation.
Furthermore, I used copy constructors instead of implementing ICloneable. The implementation is almost the same. One advantage though is that you simplify dealing with subclasses:
Suppose you had a MyAwesomeGame : MyGame, not overriding MyGame.Clone. What would you get from myAwesomeGame.Clone()? Actually, still a new MyGame because MyGame.Clone is the method in charge. One may carelessly expect a properly cloned MyAwesomeGame here, however. new MyGame(myAwesomeGame) still copies somehow incompletely, but it's more obvious. In my example I made the classes sealed to avoid this failures. If you can seal them, there's good change it will make your life simpler.
Implementing ICloneable is not recommended in general, see Why should I implement ICloneable in c#? for more detailed and general information.
Here I have an ICloneable approach anyway, to make things complete and enable you to compare and contrast:
public class MyGame : ICloneable
{
private int start;
private Board board;
public object Clone()
{
var copy = new MyGame();
copy.start = this.start;
copy.board = (Board)this.board.Clone();
return copy;
}
}
public class Board : ICloneable
{
private int count;
public object Clone()
{
var copy = new Board();
copy.count = this.count;
return copy;
}
}
The simplest and most reliable way to implement deep cloning is to serialize, and then deserialize your objects. This can have a large performance cost associated with it. Consider classes from this namespace for serialization http://msdn.microsoft.com/en-us/library/System.Xml.Serialization.aspx
Deep cloning requires recursively creating a new instance of every property that is not a value type. Cloning MyGame would require a new instance of MyGame and a new instance of Board, both populated with the same Start and Count values as their originals. This is fiddly and a nightmare to maintain. As you can guess, it is not an automatic process out of the box but it can be, using reflection (which is how the xml serialization above works.
MemberwiseClone only creates a new instance of the object you called it on - all references remain the same.
MemberwiseClone() creates a stupid shallow clone of each member of an object. This works fine when members are value types but in case of reference types it fails because it'll clone pointers and not pointed objects.
Starting from your code a memberwise clone is something like this:
public object Clone()
{
MyGame cloned = new MyGame();
cloned.Start = this.Start; // Copied (cloned) because value type
cloned.Board = this.Board; // This is not a copy, just a reference!
}
A better solution for a deep clone would be to implement ICloneable (for example, otherwise a copy constructor approach is also good) for each reference type, let's suppose Board is cloneable too:
public object Clone()
{
MyGame cloned = new MyGame();
cloned.Start = this.Start;
cloned.Board = (Board)this.Board.Clone();
}
Please note that in your example Board can implement Clone() using MemberwiseClone() because its members are all value types.
If you can't manage this (for example because code is not accesible) or you need a quick/dirty solution you may consider to user serializaiton (in memory). Which serializer is a big question, each one has some limitations (about what's serialized and how). For example XML serializer won't serialize private fields (it won't serialize fields at all). Faster one is binary formatter but you need to mark each class with a proper attribute.
Change according serializer you prefer (according to your requirements), in this case I assume you marked MyGame and Board as [Serializable] for the quick binary serialization:
public object Clone()
{
using (var stream = new MemoryStream())
{
var formatter = new BinaryFormatter();
formatter.Serialize(stream, this);
stream.Seek(0, SeekOrigin.Begin);
return formatter.Deserialize(stream);
}
}
Try this
public static T DeepCopy<T>(this T obj)
{
T result;
var serializer = new DataContractSerializer(typeof(T));
using (var ms = new MemoryStream())
{
serializer.WriteObject(ms, obj);
ms.Position = 0;
result = (T)serializer.ReadObject(ms);
ms.Close();
}
return result;
}
I have two extension methods that I use to achieve this. Demo code below:
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
namespace SimpleCloneDemo
{
public class Program
{
public static void Main(string[] args)
{
var person = new Person { Id = 1, FirstName = "John", Surname = "Doe" };
var clone = person.Clone();
clone.Id = 5;
clone.FirstName = "Jane";
Console.WriteLine(#"person: {0}", person);
Console.WriteLine(#"clone: {0}", clone);
if (Debugger.IsAttached)
Console.ReadLine();
}
}
public class Person
{
public int Id { get; set; }
public string FirstName { get; set; }
public string Surname { get; set; }
public override string ToString()
{
return string.Format("Id: {0}, Full Name: {1}, {2}", Id, Surname, FirstName);
}
}
public static class ObjectExtensions
{
public static T Clone<T>(this T entity) where T : class
{
var clone = Activator.CreateInstance(entity.GetType());
var entityPropValueDictionary = entity.AsPropValueDictionary();
foreach (var prop in clone.GetType().GetProperties())
{
clone.GetType().GetProperty(prop.Name).SetValue(clone, entityPropValueDictionary[prop.Name]);
}
return clone as T;
}
public static IDictionary<string, object> AsPropValueDictionary<T>(this T instance, params BindingFlags[] bindingFlags)
{
var runtimeBindingFlags = BindingFlags.Default;
switch (bindingFlags.Count())
{
case 0:
runtimeBindingFlags = BindingFlags.Default;
break;
case 1:
runtimeBindingFlags = bindingFlags[0];
break;
default:
runtimeBindingFlags = bindingFlags.Aggregate(runtimeBindingFlags, (current, bindingFlag) => current | bindingFlag);
break;
}
return runtimeBindingFlags == BindingFlags.Default
? instance.GetType().GetProperties().ToDictionary(prop => prop.Name, prop => prop.GetValue(instance))
: instance.GetType().GetProperties(runtimeBindingFlags).ToDictionary(prop => prop.Name, prop => prop.GetValue(instance));
}
}
}
Result:
I wrote these quick-and-dirty extension methods in a hurry so there are probably some issues with it and they are probably horribly inefficient, but they seemed to work for my use case. They may help you, too.