In C#, I have a class which has a derived property that should be serialized via XML. However, XML serialization (by default) doesn't serialize read=only properties. I can work around this by defining an empty setter like so:
public virtual string IdString
{
get { return Id.ToString("000000"); }
set { /* required for xml serialization */ }
}
But is there a cleaner more semantically correct way, short of writing my own ISerializable implementation?
Honestly this doesn't seem too bad to me as long as it is documented
You should probably throw an exception if the setter is actually called:
/// <summary>
/// Blah blah blah.
/// </summary>
/// <exception cref="NotSupportedException">Any use of the setter for this property.</exception>
/// <remarks>
/// This property is read only and should not be set.
/// The setter is provided for XML serialisation.
/// </remarks>
public virtual string IdString
{
get
{
return Id.ToString("000000");
}
set
{
throw new NotSupportedException("Setting the IdString property is not supported");
}
}
In short, no. With XmlSerializer you can either implement IXmlSerializable (which is non-trivial), or write a basic DTO (that is fully read-write) and then translate from the DTO model to your main model.
Note that in some cases DataContractSerializer is a viable option, but it doesn't offer the same control over the XML. However, with DCS you can do:
[DataMember]
public int Id { get; private set; }
With C# 8, obsoleting set is allowed, so you can do this:
public virtual string IdString
{
get { return Id.ToString("000000"); }
[Obsolete("Only used for xml serialization", error: true)]
set { throw new NotSupportedException(); }
}
This will error if anyone uses the setter accidentally.
To take the solution a little further to allow deserialization to work as well...
public class A
{
private int _id = -1;
public int Id
{
get { return _id; }
set
{
if (_id < 0)
throw new InvalidOperationException("...");
if (value < 0)
throw new ArgumentException("...");
_id = value;
}
}
}
This will allow Id to be set exactly one time to a value greater than or equal to 0. Any attempts to set it after will result in InvalidOperationException. This means that XmlSerializer will be able to set Id during deserialization, but it will never be able to be changed after. Note that if the property is a reference type then you can just check for null.
This may not be the best solution if you have a lot of read-only properties to serialize/deserialize as it would require a lot of boilerplate code. However, I've found this to be acceptable for classes with 1-2 read-only properties.
Still a hack, but this is at least a little more robust.
Related
I am confused on how XmlSerializer works behind the scenes. I have a class that deserializes XML into an object. What I am seeing is for the following two elements that are NOT part of the Xml being deserialized.
[XmlRootAttribute("MyClass", Namespace = "", IsNullable = false)]
public class MyClass
{
private string comments;
public string Comments
{
set { comments = value; }
get { return comments; }
}
private System.Collections.Generic.List<string> tests = null;
public System.Collections.Generic.List<string> Tests
{
get { return tests; }
set { tests = value; }
}
}
Let's take the following XML as an example:
<MyClass>
<SomeNode>value</SomeNode>
</MyClass>
You notice that Tests and Comments are NOT part of the XML.
When this XML gets deserialized Comments is null(which is expected) and Tests is an empty list with a count of 0.
If someone could explain this to me it would be much appreciated. What I would prefer is that if <Tests> is missing from the XML then the list should remain null, but if a (possibly empty) node <Tests /> is present then the list should get allocated.
What you are observing is that members referring to modifiable collections such as List<T> are automatically pre-allocated by XmlSerializer at the beginning of deserialization. I am not aware of any place where this behavior is documented. It may be related to the behavior described in this answer to XML Deserialization of collection property with code defaults, which explains that, since XmlSerializer supports adding to get-only and pre-allocated collections, if a pre-allocated collection contains default items then the deserialized items will be appended to it - possibly duplicating the contents. Microsoft may simply have chosen to pre-allocate all modifiable collections at the beginning of deserialization as the simplest way of implementing this.
The workaround from that answer, namely to use a surrogate array property, works here as well. Since an array cannot be appended to, XmlSerializer must accumulate all the values and set them back when deserialization is finished. But if the relevant tag is never encountered, XmlSerializer apparently does not begin accumulating values and so does not call the array setter. This seems to prevent the default pre-allocation of collections that you don't want:
[XmlRootAttribute("MyClass", Namespace = "", IsNullable = false)]
public class MyClass
{
private string comments;
public string Comments
{
set { comments = value; }
get { return comments; }
}
private System.Collections.Generic.List<string> tests = null;
[XmlIgnore]
public System.Collections.Generic.List<string> Tests
{
get { return tests; }
set { tests = value; }
}
[XmlArray("Tests")]
public string[] TestsArray
{
get
{
return (Tests == null ? null : Tests.ToArray());
}
set
{
if (value == null)
return;
(Tests = Tests ?? new List<string>(value.Length)).AddRange(value);
}
}
}
Sample .Net fiddle showing that Tests is allocated only when appropriate.
When you apply [System.Xml.Serialization.XmlElement(IsNullable = true)] to the property, the List will be null after deserialization.
Another possibility is to use the "magic" "Specified" suffix:
public bool TestsSpecified {get;set;}
If you have a serialized field/property XXX and a boolean property XXXSpecified, then the bool property is set according to whether or not the main field/property was set.
We wound up here after a google search for the same issue.
What we ended up doing was checking for Count == 0, after deserialization, and manually setting the property to null;
...
var varMyDeserializedClass = MyXmlSerializer.Deserialize(new StringReader(myInput));
if (varMyDeserializedClass.ListProperty.Count == 0)
{
varMyDeserializedClass.ListProperty = null;
}
...
It's a cheap workaround, but provides the expected result and is useful to avoid refactoring or redesign.
Using C# .NET 2.0, I have a composite data class that does have the [Serializable] attribute on it. I am creating an XMLSerializer class and passing that into the constructor:
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
I am getting an exception saying:
There was an error reflecting type.
Inside the data class there is another composite object. Does this also need to have the [Serializable] attribute, or by having it on the top object, does it recursively apply it to all objects inside?
Look at the inner exception that you are getting. It will tell you which field/property it is having trouble serializing.
You can exclude fields/properties from xml serialization by decorating them with the [XmlIgnore] attribute.
XmlSerializer does not use the [Serializable] attribute, so I doubt that is the problem.
Remember that serialized classes must have default (i.e. parameterless) constructors. If you have no constructor at all, that's fine; but if you have a constructor with a parameter, you'll need to add the default one too.
I had a similar problem, and it turned out that the serializer could not distinguish between 2 classes I had with the same name (one was a subclass of the other). The inner exception looked like this:
'Types BaseNamespace.Class1' and 'BaseNamespace.SubNamespace.Class1' both use the XML type name, 'Class1', from namespace ''. Use XML attributes to specify a unique XML name and/or namespace for the type.
Where BaseNamespace.SubNamespace.Class1 is a subclass of BaseNamespace.Class1.
What I needed to do was add an attribute to one of the classes (I added to the base class):
[XmlType("BaseNamespace.Class1")]
Note: If you have more layers of classes you need to add an attribute to them as well.
Most common reasons by me:
- the object being serialized has no parameterless constructor
- the object contains Dictionary
- the object has some public Interface members
Also be aware that XmlSerializer cannot serialize abstract properties.. See my question here (which I have added the solution code to)..
XML Serialization and Inherited Types
All the objects in the serialization graph have to be serializable.
Since XMLSerializer is a blackbox, check these links if you want to debug further into the serialization process..
Changing where XmlSerializer Outputs Temporary Assemblies
HOW TO: Debug into a .NET XmlSerializer Generated Assembly
If you need to handle specific attributes (i.e. Dictionary, or any class), you can implement the IXmlSerialiable interface, which will allow you more freedom at the cost of more verbose coding.
public class NetService : IXmlSerializable
{
#region Data
public string Identifier = String.Empty;
public string Name = String.Empty;
public IPAddress Address = IPAddress.None;
public int Port = 7777;
#endregion
#region IXmlSerializable Implementation
public XmlSchema GetSchema() { return (null); }
public void ReadXml(XmlReader reader)
{
// Attributes
Identifier = reader[XML_IDENTIFIER];
if (Int32.TryParse(reader[XML_NETWORK_PORT], out Port) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_PORT);
if (IPAddress.TryParse(reader[XML_NETWORK_ADDR], out Address) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_ADDR);
}
public void WriteXml(XmlWriter writer)
{
// Attributes
writer.WriteAttributeString(XML_IDENTIFIER, Identifier);
writer.WriteAttributeString(XML_NETWORK_ADDR, Address.ToString());
writer.WriteAttributeString(XML_NETWORK_PORT, Port.ToString());
}
private const string XML_IDENTIFIER = "Id";
private const string XML_NETWORK_ADDR = "Address";
private const string XML_NETWORK_PORT = "Port";
#endregion
}
There is an interesting article, which show an elegant way to implements a sophisticated way to "extend" the XmlSerializer.
The article say:
IXmlSerializable is covered in the official documentation, but the documentation states it's not intended for public use and provides no information beyond that. This indicates that the development team wanted to reserve the right to modify, disable, or even completely remove this extensibility hook down the road. However, as long as you're willing to accept this uncertainty and deal with possible changes in the future, there's no reason whatsoever you can't take advantage of it.
Because this, I suggest to implement you're own IXmlSerializable classes, in order to avoid too much complicated implementations.
...it could be straightforward to implements our custom XmlSerializer class using reflection.
I just got the same error and discovered that a property of type IEnumerable<SomeClass> was the problem. It appears that IEnumerable cannot be serialized directly.
Instead, one could use List<SomeClass>.
I've discovered that the Dictionary class in .Net 2.0 is not serializable using XML, but serializes well when binary serialization is used.
I found a work around here.
I recently got this in a web reference partial class when adding a new property. The auto generated class was adding the following attributes.
[System.Xml.Serialization.XmlElementAttribute(Order = XX)]
I needed to add a similar attribute with an order one higher than the last in the auto generated sequence and this fixed it for me.
I too thought that the Serializable attribute had to be on the object but unless I'm being a complete noob (I am in the middle of a late night coding session) the following works from the SnippetCompiler:
using System;
using System.IO;
using System.Xml;
using System.Collections.Generic;
using System.Xml.Serialization;
public class Inner
{
private string _AnotherStringProperty;
public string AnotherStringProperty
{
get { return _AnotherStringProperty; }
set { _AnotherStringProperty = value; }
}
}
public class DataClass
{
private string _StringProperty;
public string StringProperty
{
get { return _StringProperty; }
set{ _StringProperty = value; }
}
private Inner _InnerObject;
public Inner InnerObject
{
get { return _InnerObject; }
set { _InnerObject = value; }
}
}
public class MyClass
{
public static void Main()
{
try
{
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
TextWriter writer = new StreamWriter(#"c:\tmp\dataClass.xml");
DataClass clazz = new DataClass();
Inner inner = new Inner();
inner.AnotherStringProperty = "Foo2";
clazz.InnerObject = inner;
clazz.StringProperty = "foo";
serializer.Serialize(writer, clazz);
}
finally
{
Console.Write("Press any key to continue...");
Console.ReadKey();
}
}
}
I would imagine that the XmlSerializer is using reflection over the public properties.
Sometime, this type of error is because you dont have constructur of class without argument
I had a situation where the Order was the same for two elements in a row
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "SeriousInjuryFlag")]
.... some code ...
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "AccidentFlag")]
When I changed the code to increment the order by one for each new Property in the class, the error went away.
I was getting the same error when I created a property having a datatype - Type. On this, I was getting an error - There was an error reflecting type. I kept checking the 'InnerException' of every exception from the debug dock and got the specific field name (which was Type) in my case. The solution is as follows:
[XmlIgnore]
public Type Type { get; set; }
Also note that you cannot serialize user interface controls and that any object you want to pass onto the clipboard must be serializable otherwise it cannot be passed across to other processes.
I have been using the NetDataSerialiser class to serialise
my domain classes. NetDataContractSerializer Class.
The domain classes are shared between client and server.
I had the same issue and in my case the object had a ReadOnlyCollection. A collection must implement Add method to be serializable.
I have a slightly different solution to all described here so far, so for any future civilisation here's mine!
I had declared a datatype of "time" as the original type was a TimeSpan and subsequently changed to a String:
[System.Xml.Serialization.XmlElementAttribute(DataType="time", Order=3)]
however the actual type was a string
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
by removing the DateType property the Xml can be serialized
[System.Xml.Serialization.XmlElementAttribute(Order=3)]
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
[System.Xml.Serialization.XmlElementAttribute("strFieldName", Form = System.Xml.Schema.XmlSchemaForm.Unqualified)]
Or
[XmlIgnore]
string [] strFielsName {get;set;}
In the code base I was maintaining I found this exact class, pasted below. In logPath property, gets does some work. I would think that it is better to do the work in set - that way it will be done only once. However, partly because this is how the class is written, partly because it is an xml-mapped property, and partly because I am afraid that I might miss something in a debugger, I have doubts.
Additionally, if an element never existed in the xml, and it happened to be optional, then I think I will get a null for the value. I might actually want to differentiate between having no element and receiving empty value. I suppose I can have a private bool member which can help me detect that - that would be an argument for doing work in set rather than get. So, code optimizers work hard these days, so performance is rarely a true concern. It is more of a "figure this out once and do not think about it later" things. This is just one example, and properties frequently do some massaging.
Would you say that it is always better to do work in set? In get? It depends? A mixed style would not bother you a single bit as long as it works?
Thanks.
namespace MyNamespace
{
using System;
using System.Xml.Serialization;
/// <summary>
/// The LoggingListener class encapsulates the "logListener"
/// element of config file, and puts the "logPath"
/// attribute in a file path string.
/// </summary>
public class LoggingListener
{
private string logPathValue;
/// <summary>
/// Gets or sets the LOCAL file path to a log file
/// which will be written during operation of the Updater.
/// </summary>
[XmlAttribute("logPath")]
public string LogPath
{
get
{
return this.logPathValue == null ?
String.Empty : this.logPathValue;
}
set
{
this.logPathValue = value;
}
}
}
}
EDIT: In this given sample ... if the log file is not there, then no logging should take place.
I'd certainly prefer consistency. But the fact is in cases like this it often will not matter. I'm sure the original developer's intent was to avoid the infuriating NullReferenceException bug resulting from attempting to access the LogPath property of some LoggingListener object -- in which case, it probably just seemed most sensible to put the null check in the get (since that's where the exception was thrown).
In general, I'd agree with you that perhaps it makes the most sense to put it in the set -- but then, there's no guaranteeing LogPath will never return null, as the private member could have been set to null from within the class, or perhaps it was never set at all (as Kevin pointed out).
I tend to go with a somewhat hybrid approach: make the property read-only, and make sure it gets set to something non-null in the constructor:
public class LoggingListener {
private readonly string _logPath;
public LoggingListener(string logPath) {
_logPath = logPath ?? string.Empty;
}
public string LogPath {
get { return _logPath; }
}
}
Whether this is an acceptable compromise obviously depends on your specific needs. Also, whether the property should really never be null after all is certainly debatable, depending on the scenario, as you've already remarked.
I personally don't like when property changes assigned value in either get or set accessor. It changes expected property behavior:
var value = null;
var listener = new LoggingListener();
listener.LogPath = value;
if(listener.LogPath != value)
{
// how could we get here?
}
Instead, I prefer to clearly decide, whether property can accept null or not. If it can, it shouldn't do any work in get/set, if yes, it should neither return null nor accept it as a value.
If there is no way to prevent assignment of null, than i would prefer to handle this case in set accessor.
With getters and setters I follow a few rules:
No side effects - don't modify 'B' when you put a value in 'A'
What I put in 'A' comes out of 'A', if you need to modify 'A' expose a new read-only property
If you don't like my value for 'A', tell me now not later when I call a method
Outside of a data model, do not accept or return null
For your example I prefer seeing the following:
public class LoggingListener
{
private string logPathValue = String.Empty;
[XmlAttribute("logPath")]
public string LogPath
{
get { return logPathValue; }
set
{
if(value == null) throw new ArgumentNullException();
this.logPathValue = value;
}
}
}
Yet it's clear to me why you ask, it really about the behavior of "XmlAttribute" and the XmlSerializer. You can use the "DefaultValueAttribute" from the ComponentModel namespace, or use an XSD to provide the defaults, or expose a new property and/or method. You could also try creating an interface to separate concerns, something like the following:
public class LoggingListener : ILogListenerSettings
{
private string logPathValue;
[XmlAttribute("logPath")]
public string LogPath
{
get { return logPathValue; }
set { logPathValue = value; }
}
string ILogListenerSettings.FullLogPath
{
get
{
string path = logPathValue;
if(String.IsNullOrEmpty(path))
path = Environment.CurrentDirectory;
path = Path.GetFullPath(path);
Directory.Create(path);
return path;
}
}
}
the only way to be sure that logPathValue is initialized is to do it yourself...
public class LoggingListener
{
private string logPathValue = string.Empty;
I'm refactoring some objects that are serialized to XML but need to keep a few properties for backwards compatibility, I've got a method that converts the old object into the new one for me and nulls the obsolete property. I want to use the Obsolete attribute to tell other developers not to use this property but it is causing the property to be ignored by the XmlSerializer.
Similar Code:
[Serializable]
public class MySerializableObject
{
private MyObject _oldObject;
private MyObject _anotherOldObject;
private MyObject _newBetterObject;
[Obsolete("Use new properties in NewBetterObject to prevent duplication")]
public MyObject OldObject
{
get { return _oldObject; }
set { _oldObject = value; }
}
[Obsolete("Use new properties in NewBetterObject to prevent duplication")]
public MyObject AnotherOldObject
{
get { return _anotherOldObject; }
set { _anotherOldObject = value; }
}
public MyObject NewBetterObject
{
get { return _anotherOldObject; }
set { _anotherOldObject = value; }
}
}
Any ideas on a workaround? My best solution is to write obsolete in the XML comments...
Update: I'm using .NET 2.0
EDIT: After reading a MS Connect article, it appears that .Net 2.0 has a 'feature' where it makes ObsoleteAttribute equivalent to XmlIgnoreAttribute without any notification in the documentation. So I'm going to revise my answer to say that the only way to have your cake and eat it too in this instance is to follow #Will's advice and implement serialization manually. This will be your only future proof way of including Obsolete properties in your XML. It is not pretty in .Net 2.0, but .Net 3.0+ can make life easier.
From XmlSerializer:
Objects marked with the Obsolete Attribute no longer serialized
In the .NET Framework 3.5 the XmlSerializer class no longer serializes objects that are marked as [Obsolete].
Another workaround is to subscribe to XmlSerializer.UnknownElement, when creating the serializer for the datatype, and then fix old data that way.
http://weblogs.asp.net/psteele/archive/2011/01/31/xml-serialization-and-the-obsolete-attribute.aspx
Maybe consider to have the method for subscribing as a static method on the class for datatype.
static void serializer_UnknownElement(object sender, XmlElementEventArgs e)
{
if( e.Element.Name != "Hobbies")
{
return;
}
var target = (MyData) e.ObjectBeingDeserialized;
foreach(XmlElement hobby in e.Element.ChildNodes)
{
target.Hobbies.Add(hobby.InnerText);
target.HobbyData.Add(new Hobby{Name = hobby.InnerText});
}
}
I have struggled with this a lot - there is no solution other than doing serialization manually or using another serializer.
However, instead of writing shims for each obsolete property which quickly becomes a pain, you could consider adding an Obsolete prefix to property names (e.g. Foo becomes ObsoleteFoo. This will not generate a compiler warning like the attribute will, but at least it's visible in code.
1) WAG: Try adding the XmlAttributeAttribute to the property; perhaps this will override the ObsoleteAttribute
2) PITA: Implement IXmlSerializable
Yes I agree with marking things with the name "Obsolete" we do this with Enum values
/// <summary>
/// Determines the swap file location for a cluster.
/// </summary>
/// <remarks>This enum contains the original text based values for backwards compatibility with versions previous to "8.1".</remarks>
public enum VMwareClusterSwapFileLocation
{
/// <summary>
/// The swap file location is unknown.
/// </summary>
Unknown = 0,
/// <summary>
/// The swap file is stored in the virtual machine directory.
/// </summary>
VmDirectory = 1,
/// <summary>
/// The swap file is stored in the datastore specified by the host.
/// </summary>
HostLocal = 2,
/// <summary>
/// The swap file is stored in the virtual machine directory. This value is obsolete and used for backwards compatibility.
/// </summary>
[XmlElement("vmDirectory")]
ObseleteVmDirectory = 3,
/// <summary>
/// The swap file is stored in the datastore specified by the host. This value is obsolete and used for backwards compatibility.
/// </summary>
[XmlElement("hostLocal")]
ObseleteHostLocal = 4,
}
You may try the following workaround:
add a method named
ShouldSerializeOldObject ()
{
return true;
}
ShouldSerializeAnotherOldObject ()
{
return true
}
this may override the obsolete Attribute
Using C# .NET 2.0, I have a composite data class that does have the [Serializable] attribute on it. I am creating an XMLSerializer class and passing that into the constructor:
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
I am getting an exception saying:
There was an error reflecting type.
Inside the data class there is another composite object. Does this also need to have the [Serializable] attribute, or by having it on the top object, does it recursively apply it to all objects inside?
Look at the inner exception that you are getting. It will tell you which field/property it is having trouble serializing.
You can exclude fields/properties from xml serialization by decorating them with the [XmlIgnore] attribute.
XmlSerializer does not use the [Serializable] attribute, so I doubt that is the problem.
Remember that serialized classes must have default (i.e. parameterless) constructors. If you have no constructor at all, that's fine; but if you have a constructor with a parameter, you'll need to add the default one too.
I had a similar problem, and it turned out that the serializer could not distinguish between 2 classes I had with the same name (one was a subclass of the other). The inner exception looked like this:
'Types BaseNamespace.Class1' and 'BaseNamespace.SubNamespace.Class1' both use the XML type name, 'Class1', from namespace ''. Use XML attributes to specify a unique XML name and/or namespace for the type.
Where BaseNamespace.SubNamespace.Class1 is a subclass of BaseNamespace.Class1.
What I needed to do was add an attribute to one of the classes (I added to the base class):
[XmlType("BaseNamespace.Class1")]
Note: If you have more layers of classes you need to add an attribute to them as well.
Most common reasons by me:
- the object being serialized has no parameterless constructor
- the object contains Dictionary
- the object has some public Interface members
Also be aware that XmlSerializer cannot serialize abstract properties.. See my question here (which I have added the solution code to)..
XML Serialization and Inherited Types
All the objects in the serialization graph have to be serializable.
Since XMLSerializer is a blackbox, check these links if you want to debug further into the serialization process..
Changing where XmlSerializer Outputs Temporary Assemblies
HOW TO: Debug into a .NET XmlSerializer Generated Assembly
If you need to handle specific attributes (i.e. Dictionary, or any class), you can implement the IXmlSerialiable interface, which will allow you more freedom at the cost of more verbose coding.
public class NetService : IXmlSerializable
{
#region Data
public string Identifier = String.Empty;
public string Name = String.Empty;
public IPAddress Address = IPAddress.None;
public int Port = 7777;
#endregion
#region IXmlSerializable Implementation
public XmlSchema GetSchema() { return (null); }
public void ReadXml(XmlReader reader)
{
// Attributes
Identifier = reader[XML_IDENTIFIER];
if (Int32.TryParse(reader[XML_NETWORK_PORT], out Port) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_PORT);
if (IPAddress.TryParse(reader[XML_NETWORK_ADDR], out Address) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_ADDR);
}
public void WriteXml(XmlWriter writer)
{
// Attributes
writer.WriteAttributeString(XML_IDENTIFIER, Identifier);
writer.WriteAttributeString(XML_NETWORK_ADDR, Address.ToString());
writer.WriteAttributeString(XML_NETWORK_PORT, Port.ToString());
}
private const string XML_IDENTIFIER = "Id";
private const string XML_NETWORK_ADDR = "Address";
private const string XML_NETWORK_PORT = "Port";
#endregion
}
There is an interesting article, which show an elegant way to implements a sophisticated way to "extend" the XmlSerializer.
The article say:
IXmlSerializable is covered in the official documentation, but the documentation states it's not intended for public use and provides no information beyond that. This indicates that the development team wanted to reserve the right to modify, disable, or even completely remove this extensibility hook down the road. However, as long as you're willing to accept this uncertainty and deal with possible changes in the future, there's no reason whatsoever you can't take advantage of it.
Because this, I suggest to implement you're own IXmlSerializable classes, in order to avoid too much complicated implementations.
...it could be straightforward to implements our custom XmlSerializer class using reflection.
I just got the same error and discovered that a property of type IEnumerable<SomeClass> was the problem. It appears that IEnumerable cannot be serialized directly.
Instead, one could use List<SomeClass>.
I've discovered that the Dictionary class in .Net 2.0 is not serializable using XML, but serializes well when binary serialization is used.
I found a work around here.
I recently got this in a web reference partial class when adding a new property. The auto generated class was adding the following attributes.
[System.Xml.Serialization.XmlElementAttribute(Order = XX)]
I needed to add a similar attribute with an order one higher than the last in the auto generated sequence and this fixed it for me.
I too thought that the Serializable attribute had to be on the object but unless I'm being a complete noob (I am in the middle of a late night coding session) the following works from the SnippetCompiler:
using System;
using System.IO;
using System.Xml;
using System.Collections.Generic;
using System.Xml.Serialization;
public class Inner
{
private string _AnotherStringProperty;
public string AnotherStringProperty
{
get { return _AnotherStringProperty; }
set { _AnotherStringProperty = value; }
}
}
public class DataClass
{
private string _StringProperty;
public string StringProperty
{
get { return _StringProperty; }
set{ _StringProperty = value; }
}
private Inner _InnerObject;
public Inner InnerObject
{
get { return _InnerObject; }
set { _InnerObject = value; }
}
}
public class MyClass
{
public static void Main()
{
try
{
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
TextWriter writer = new StreamWriter(#"c:\tmp\dataClass.xml");
DataClass clazz = new DataClass();
Inner inner = new Inner();
inner.AnotherStringProperty = "Foo2";
clazz.InnerObject = inner;
clazz.StringProperty = "foo";
serializer.Serialize(writer, clazz);
}
finally
{
Console.Write("Press any key to continue...");
Console.ReadKey();
}
}
}
I would imagine that the XmlSerializer is using reflection over the public properties.
Sometime, this type of error is because you dont have constructur of class without argument
I had a situation where the Order was the same for two elements in a row
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "SeriousInjuryFlag")]
.... some code ...
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "AccidentFlag")]
When I changed the code to increment the order by one for each new Property in the class, the error went away.
I was getting the same error when I created a property having a datatype - Type. On this, I was getting an error - There was an error reflecting type. I kept checking the 'InnerException' of every exception from the debug dock and got the specific field name (which was Type) in my case. The solution is as follows:
[XmlIgnore]
public Type Type { get; set; }
Also note that you cannot serialize user interface controls and that any object you want to pass onto the clipboard must be serializable otherwise it cannot be passed across to other processes.
I have been using the NetDataSerialiser class to serialise
my domain classes. NetDataContractSerializer Class.
The domain classes are shared between client and server.
I had the same issue and in my case the object had a ReadOnlyCollection. A collection must implement Add method to be serializable.
I have a slightly different solution to all described here so far, so for any future civilisation here's mine!
I had declared a datatype of "time" as the original type was a TimeSpan and subsequently changed to a String:
[System.Xml.Serialization.XmlElementAttribute(DataType="time", Order=3)]
however the actual type was a string
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
by removing the DateType property the Xml can be serialized
[System.Xml.Serialization.XmlElementAttribute(Order=3)]
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
[System.Xml.Serialization.XmlElementAttribute("strFieldName", Form = System.Xml.Schema.XmlSchemaForm.Unqualified)]
Or
[XmlIgnore]
string [] strFielsName {get;set;}