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C# / MongoDB - Serialize Enum Dictionary Keys to String

I am attempting to serialize a dictionary of dictionaries where the parent dictionary has its keys as type enum and child dictionary has keys of type DateTime. While attempting to insert into my collection I am met with
When using DictionaryRepresentation.Document key values must serialize as strings
I have read forums discussing serialization of enum into string, however with the model definitions that are currently in place I'm not sure how to go about with this method.
The two dictionary models that are currently in use are simply implementations of the Dictionary class:
IndexValues
{
public class IndexValues : Dictionary<Index, DateDictionary> { }
}
DateDictionary
public class DateDictionary : Dictionary<DateTime, double>
{
public double AsOf(DateTime d)
{
DateTime date = d;
while (date >= Keys.Min())
{
if (TryGetValue(date, out var value))
{
return value;
}
date = date.AddDays(-1);
}
throw new Exception($"The dictionary doesn't have a value for any date less than or equal to {d}.");
}
}
Index
public enum Index
{
SPX,
NDX
}
I am adding values to the dictionary in my main program by simply instantiating new instances of both classes and adding the values in the required types.
IndexValues indexRecords = new IndexValues();
...
var enumHead = (Index)Enum.Parse(typeof(Index), header[l]); // header is simply a list of strings
...
DateDictionary dateDict = new DateDictionary();
var date = Convert.ToDateTime(dataLine[j]); // dataLine is simply a list of strings
var value = Convert.ToDouble(dataLine[k]);
if (indexRecords.ContainsKey(enumHead))
{
indexRecords[enumHead].Add(date, value);
}
else
{
dateDict.Add(date, value);
indexRecords.Add(enumHead, dateDict);
}
I have attempted defining the key and value within the model definitions and using both [BsonRepresentation(BsonType.String)] for the enum and DateTime values and [BsonDictionaryOptions(DictionaryRepresentation.Document)] for the DateDictionary, but am still met with the same issue.
What am I missing in this instance, and what would be the correct direction to look towards? For reference, I am using the C# driver v2.8.1.

It turns out I was needing two serializers instead of one. I defined these globally and I was able to insert without an issue.
BsonSerializer.RegisterSerializer(new EnumSerializer<Index>(BsonType.String));
BsonSerializer.RegisterSerializer(new DateTimeSerializer(DateTimeKind.Local, BsonType.String));

Can I access a class variable with another variable?

i want to do a class constructor that takes a dicionary as parameter and initialize all the class variables that are listed as key in the dictionary, after of course a type conversion:
public class User
{
public int id;
public string username;
public string password;
public string email;
public int mana_fire;
public int mana_water;
public int mana_earth;
public int mana_life;
public int mana_death;
public User ()
{
}
public User(Dictionary<string,string> dataArray){
FieldInfo[] classVariablesInfoList = typeof(User).GetFields();
for(int i = 0; i < classVariablesInfoList.Length; i++)
{
if(dataArray.ContainsKey(classVariablesInfoList[i].Name)){
//missing code here :)
//need something like classVariable= dataArray["classVariablesInfolist[i].name"]; ?
}
}
}
}
but i can't find out how to do this!
Can you please help? :)

You can use the SetValue frunction from reflection:
FieldInfo f = classVariablesInfoList[i];
if (f.ReflectedType == typeof(int))
{
f.SetValue(this, Convert.ToInt32(dataArray[f.Name]));
}
else
{
f.SetValue(this, dataArray[classVariablesInfoList[i].Name]);
}
But it is a really uncommon way to do this with a dictionary. You should considder accessing the fields directly or add parameters to the constructor for any field. And fields should never be public - use properties instead.

The following will work if Convert.ChangeType() is able to handle the conversion. There are a lot of problems waiting to occur, for example handling numbers or dates where the string representation depends on the locale. I would really suggest to use usual typed constructor parameters or standard (de)serialization mechanism if possible. Or at least use a dictionary containing objects instead of strings to get rid of the conversion, again if possible.
public User(Dictionary<String, String> data)
{
var fields = typeof(User).GetFields();
foreach (field in fields)
{
if (data.ContainsKey(field.Name))
{
var value = Convert.ChangeType(data[field.Name], field.MemberType);
field.SetValue(this, value);
}
}
}

I would like to separate your problem into two parts.
1. Applying conversion
The FieldInfo type present a FieldType property that is the actual type of the field, using this Type we can use the non-generic ChangeType method of System.Convert, this method will be able convert some types to others. Luckily it support String to Int.
Usage:
Convert.ChangeType(OLD_VALUE, TARGET_TYPE);
2. Setting the field
The field info class has a SetValue method (FieldInfo.SetValue), it has two parameters, the first one is the current (ie. this) instance (or the instance you wish to change). the second is the new value you wish to set.
Putting it all together
[...]
var fieldInfo = classVariablesInfoList[i];
var name = fieldInfo.Name;
var targetType = fieldInfo.Type;
var value = Convert.ChangeType(dataArray[name], targetType);
classVariablesInfoList[i].SetValue(this, value);

Using LINQ to create a List<T> where T : someClass<U>

This is related to a prior question of mine C# Generic List conversion to Class implementing List<T>
I have the following code:
public abstract class DataField
{
public string Name { get; set; }
}
public class DataField<T> : DataField
{
public T Value { get; set; }
}
public static List<DataField> ConvertXML(XMLDocument data) {
result = (from d in XDocument.Parse(data.OuterXML).Root.Decendendants()
select new DataField<string>
{
Name = d.Name.ToString(),
Value = d.Value
}).Cast<DataField>().ToList();
return result;
}
This works however I would like to be able to modify the select portion of the LINQ query to be something like this:
select new DataField<[type defined in attribute of XML Element]>
{
Name = d.Name.ToString(),
Value = d.Value
}
Is this just a poor approach? is it possible? Any suggestions?

Here is a working solution: (You must specify fully qualified type names for your Type attribute otherwise you have to configure a mapping somehow...)
I used the dynamic keyword, you can use reflection to set the value instead if you do not have C# 4...
public static void Test()
{
string xmlData = "<root><Name1 Type=\"System.String\">Value1</Name1><Name2 Type=\"System.Int32\">324</Name2></root>";
List<DataField> dataFieldList = DataField.ConvertXML(xmlData);
Debug.Assert(dataFieldList.Count == 2);
Debug.Assert(dataFieldList[0].GetType() == typeof(DataField<string>));
Debug.Assert(dataFieldList[1].GetType() == typeof(DataField<int>));
}
public abstract class DataField
{
public string Name { get; set; }
/// <summary>
/// Instanciate a generic DataField<T> given an XElement
/// </summary>
public static DataField CreateDataField(XElement element)
{
//Determine the type of element we deal with
string elementTypeName = element.Attribute("Type").Value;
Type elementType = Type.GetType(elementTypeName);
//Instanciate a new Generic element of type: DataField<T>
dynamic dataField = Activator.CreateInstance(typeof(DataField<>).MakeGenericType(elementType));
dataField.Name = element.Name.ToString();
//Convert the inner value to the target element type
dynamic value = Convert.ChangeType(element.Value, elementType);
//Set the value into DataField
dataField.Value = value;
return dataField;
}
/// <summary>
/// Take all the descendant of the root node and creates a DataField for each
/// </summary>
public static List<DataField> ConvertXML(string xmlData)
{
var result = (from d in XDocument.Parse(xmlData).Root.DescendantNodes().OfType<XElement>()
select CreateDataField(d)).ToList();
return result;
}
}
public class DataField<T> : DataField
{
public T Value { get; set; }
}

You cannot do this easily in C#. The generic type argument has to specified at compile time. You can use reflection to do otherwise
int X = 1;
Type listype = typeof(List<>);
Type constructed = listype.MakeGenericType( X.GetType() );
object runtimeList = Activator.CreateInstance(constructed);
Here we have just created a List<int>. You can do it with your type

Different instances of a generic class are actually different classes.
I.e. DataField<string> and DataField<int> are not the same class at all(!)
This means, that you can not define the generic parameter during run-time, as it has to be determined during compile-time.

I would say this is a poor approach. In reality, even after you parse your XML file, you're not going to know what types of "DataFields" you have. You might as well just parse them as objects.
However, if you know that you're only ever going to have x number of types, you can do like so:
var Dictionary<string, Func<string, string, DataField>> myFactoryMaps =
{
{"Type1", (name, value) => { return new DataField<Type1>(name, Type1.Parse(value); } },
{"Type2", (name, value) => { return new DataField<Type2>(name, Type2.Parse(value); } },
};

Termit's answer is certainly excellent. Here is a little variant.
public abstract class DataField
{
public string Name { get; set; }
}
public class DataField<T> : DataField
{
public T Value { get; set; }
public Type GenericType { get { return this.Value.GetType(); } }
}
static Func<XElement , DataField> dfSelector = new Func<XElement , DataField>( e =>
{
string strType = e.Attribute( "type" ).Value;
//if you dont have an attribute type, you could call an extension method to figure out the type (with regex patterns)
//that would only work for struct
Type type = Type.GetType( strType );
dynamic df = Activator.CreateInstance( typeof( DataField<>).MakeGenericType( type ) );
df.Name = e.Attribute( "name" ).Value;
dynamic value = Convert.ChangeType( e.Value , type );
df.Value = value;
return df;
} );
public static List<DataField> ConvertXML( string xmlstring )
{
var result = XDocument.Parse( xmlstring )
.Root.Descendants("object")
.Select( dfSelector )
.ToList();
return result;
}
static void Main( string[] args )
{
string xml = "<root><object name=\"im1\" type=\"System.String\">HelloWorld!</object><object name=\"im2\" type=\"System.Int32\">324</object></root>";
List<DataField> dfs = ConvertXML( xml );
}

you can create generic type by reflection
var instance = Activator.CreateInstance( typeof(DataField)
.MakeGenericType(Type.GetType(typeNameFromAttribute) );
// and here set properties also by reflection

#Termit and #Burnzy put forward good solutions involving factory methods.
The problem with that is that you're loading up your parsing routine with a bunch of extra logic (more testing, more errors) for dubious returns.
Another way to do it would be to use a simplified string-based DataField with typed read methods - the top answer for this question.
An implementation of a typed-value method that would be nice but only works for value types (which does not include strings but does include DateTimes):
public T? TypedValue<T>()
where T : struct
{
try { return (T?) Convert.ChangeType(this.Value, typeof(T)); }
catch { return null; }
}
I'm assuming that you're wanting to use the type information to do things like dynamically assigning user-controls to the field, validation rules, correct SQL types for persistence etc.
I've done a lot of this sort of thing with approaches that seem a bit like yours.
At the end of the day you should seperate your metadata from your code - #Burnzy's answer chooses the code based on the metadata (a "type" attribute of the DataField element) and is a very simple example of this.
If you're dealing with XML, XSDs are a very useful and extensible form of metadata.
As far as what you store each field's data in - use strings because:
they are nullable
they can store partial values
they can store invalid values (makes telling the user to sort their act out more transparent)
they can store lists
special cases won't invade unrelated code because there aren't any
learn regular expressions, validate, be happy
you can convert them to stronger types really easily
I found it very rewarding to develop little frameworks like this - it is a learning experience and you'll come out understanding a lot more about UX and the reality of modelling from it.
There are four groups of test cases that I would advise you to tackle first:
Dates, Times, Timestamps (what I call DateTime), Periods (Timespan)
in particular, make sure you test having a different server locality from the client's.
lists - multi-select foreign keys etc
null values
invalid input - this generally involves retaining the original value
Using strings simplifies all this greatly because it allows you to clearly demarcate responsibilities within your framework. Think about doing fields containing lists in your generic model - it gets hairy rather quickly and it is easy to end up with a special case for lists in pretty much every method. With strings, the buck stops there.
Finally, if you want a solid implementation of this sort of stuff without having to do anything much, consider DataSets - old school I know - they do all sorts of wonderful things you wouldn't expect but you do have to RTFM.
The main downfall of that idea would be that it isn't compatible with WPF data binding - though my experience has been that reality isn't compatible with WPF data binding.
I hope I interpreted your intentions correctly - good luck either way :)

Unfortunately, there no inheritance relation between C<T> and C<string> for instance.
However, you can inherit from a common non-generic class and in addition to this implement a generic interface.
Here I use explicit interface implementation in order to be able to declare a Value property typed as object, as well as a more specifically typed Value property.
The Values are read-only and can only be assigned through a typed constructor parameter. My construction is not perfect, but type safe and doesn't use reflection.
public interface IValue<T>
{
T Value { get; }
}
public abstract class DataField
{
public DataField(string name, object value)
{
Name = name;
Value = value;
}
public string Name { get; private set; }
public object Value { get; private set; }
}
public class StringDataField : DataField, IValue<string>
{
public StringDataField(string name, string value)
: base(name, value)
{
}
string IValue<string>.Value
{
get { return (string)Value; }
}
}
public class IntDataField : DataField, IValue<int>
{
public IntDataField(string name, int value)
: base(name, value)
{
}
int IValue<int>.Value
{
get { return (int)Value; }
}
}
The list can then be declared with the abstract base class DataField as generic parameter:
var list = new List<DataField>();
switch (fieldType) {
case "string":
list.Add(new StringDataField("Item", "Apple"));
break;
case "int":
list.Add(new IntDataField("Count", 12));
break;
}
Access the strongly typed field through the interface:
public void ProcessDataField(DataField field)
{
var stringField = field as IValue<string>;
if (stringField != null) {
string s = stringField.Value;
}
}

While the other questions mostly proposed an elegant solution to convert your XML elements to a generic class instance, I'm going to deal with the consequences of taking the approach to model the DataField class as a generic like DataField<[type defined in attribute of XML Element]>.
After selecting your DataField instance into the list you want to use these fields. Her polymorphism comes into play! You want to iterate your DataFields an treat them in a uniform way. Solutions that use generics often end up in a weird switch/if orgy since there is no easy way to associate behavior based on the generic type in c#.
You might have seen code like this (I'm trying to calculate the sum of all numeric DataField instances)
var list = new List<DataField>()
{
new DataField<int>() {Name = "int", Value = 2},
new DataField<string>() {Name = "string", Value = "stringValue"},
new DataField<float>() {Name = "string", Value = 2f},
};
var sum = 0.0;
foreach (var dataField in list)
{
if (dataField.GetType().IsGenericType)
{
if (dataField.GetType().GetGenericArguments()[0] == typeof(int))
{
sum += ((DataField<int>) dataField).Value;
}
else if (dataField.GetType().GetGenericArguments()[0] == typeof(float))
{
sum += ((DataField<float>)dataField).Value;
}
// ..
}
}
This code is a complete mess!
Let's go try the polymorphic implementation with your generic type DataField and add some method Sum to it that accepts the old some and returns the (possibly modified) new sum:
public class DataField<T> : DataField
{
public T Value { get; set; }
public override double Sum(double sum)
{
if (typeof(T) == typeof(int))
{
return sum + (int)Value; // Cannot really cast here!
}
else if (typeof(T) == typeof(float))
{
return sum + (float)Value; // Cannot really cast here!
}
// ...
return sum;
}
}
You can imagine that your iteration code gets a lot clearer now but you still have this weird switch/if statement in you code. And here comes the point: Generics do not help you here it's the wrong tool at the wrong place. Generics are designed in C# for giving you compile time type safety to avoid potential unsafe cast operations. They additionally add to code readability but that's not the case here :)
Let's take a look at the polymorphic solution:
public abstract class DataField
{
public string Name { get; set; }
public object Value { get; set; }
public abstract double Sum(double sum);
}
public class IntDataField : DataField
{
public override double Sum(double sum)
{
return (int)Value + sum;
}
}
public class FloatDataField : DataField
{
public override double Sum(double sum)
{
return (float)Value + sum;
}
}
I guess you will not need too much fantasy to imagine how much adds to your code's readability/quality.
The last point is how to create instances of these classes. Simply by using some convention TypeName + "DataField" and Activator:
Activator.CreateInstance("assemblyName", typeName);
Short Version:
Generics is not the appropriate approach for your problem because it does not add value to the handling of DataField instances. With the polymorphic approach you can work easily with the instances of DataField!

It's not impossible as you can do this with reflection. But this isn't what generics were designed for and isn't how it should be done. If you're going to use reflection to make the generic type, you may as well not use a generic type at all and just use the following class:
public class DataField
{
public string Name { get; set; }
public object Value { get; set; }
}

You'll need to insert the logic for determining the data type from your XML and add all the types you need to use but this should work:
result = (from d in XDocument.Parse(data.OuterXML).Root.Descendants()
let isString = true //Replace true with your logic to determine if it is a string.
let isInt = false //Replace false with your logic to determine if it is an integer.
let stringValue = isString ? (DataField)new DataField<string>
{
Name = d.Name.ToString(),
Value = d.Value
} : null
let intValue = isInt ? (DataField)new DataField<int>
{
Name = d.Name.ToString(),
Value = Int32.Parse(d.Value)
} : null
select stringValue ?? intValue).ToList();

Architecturally speaking, how should I replace an extremely large switch statement with something more manageable?

EDIT 1: Forgot to add the nested property curve ball.
UPDATE: I have chosen #mtazva's answer as that was the preferred solution for my specific case. In retrospect, I asked a general question with a very specific example and I believe that ended up confusing everyone (or maybe just me) as to what the question was exactly. I do believe the general question has been answered as well (see the Strategy pattern answers and links). Thanks everyone!
Large switch statements obviously smell and I have seen some links on how you could do this with a dictionary that maps to functions. But I'm wondering if there is a better (or smarter way) to do this? In a way, this is a question I've always sort of had rolling around in the back of my head but never really had a good solution to.
This question stemmed from another question I asked earlier: How to select all the values of an object's property on a list of typed objects in .Net with C#
Here is an example class I'm working with (from an external source):
public class NestedGameInfoObject
{
public string NestedName { get; set; }
public int NestedIntValue { get; set; }
public decimal NestedDecimalValue { get; set; }
}
public class GameInfo
{
public int UserId { get; set; }
public int MatchesWon { get; set; }
public long BulletsFired { get; set; }
public string LastLevelVisited { get; set; }
public NestedGameInfoObject SuperCoolNestedGameInfo { get; set; }
// thousands more of these
}
Unfortunately, this is coming from an external source... imagine a HUGE data dump from Grand Theft Auto or something.
And I want to get just a small cross section of a list of these objects. Imagine we want to be able to compare you with a bunch of your friends' game info objects. An individual result for one user would look like this:
public class MyResult
{
public int UserId { get; set; } // user id from above object
public string ResultValue { get; set; } // one of the value fields from above with .ToString() executed on it
}
And an example of what I want to replace with something more manageable (believe me, I DON'T want to be maintaining this monster switch statement):
const int MATCHES_WON = 1;
const int BULLETS_FIRED = 2;
const int NESTED_INT = 3;
public static List<MyResult> GetMyResult(GameInfo[] gameInfos, int input)
{
var output = new List<MyResult>();
switch(input)
{
case MATCHES_WON:
output = gameInfos.Select(x => new MyResult()
{
UserId = x.UserId,
ResultValue = x.MatchesWon.ToString()
}).ToList<MyResult>();
break;
case BULLETS_FIRED:
output = gameInfos.Select(x => new MyResult()
{
UserId = x.UserId,
ResultValue = x.BulletsFired.ToString()
}).ToList<MyResult>();
break;
case NESTED_INT:
output = gameInfos.Select(x => new MyResult()
{
UserId = x.UserId,
ResultValue = x.SuperCoolNestedGameInfo.NestedIntValue.ToString()
}).ToList<MyResult>();
break;
// ad nauseum
}
return output;
}
So the question is are there any reasonable ways to manage this beast? What I'd really like is a dynamic way to get this info in case that initial object changes (more game info properties are added, for instance). Is there a better way to architect this so it's less clumsy?

I think your first sentence eluded to what is probably the most reasonable solution: some form of dictionary mapping values to methods.
For example, you could define a static Dictionary<int, func<GameInfo, string>>, where each value such as MATCHES_WON would be added with a corresponding lambda that extracts the appropriate value (assuming your constants, etc are defined as shown in your example):
private static Dictionary<int, Func<GameInfo, string>> valueExtractors =
new Dictionary<int, Func<GameInfo, string>>() {
{MATCHES_WON, gi => gi.MatchesWon.ToString()},
{BULLETS_FIRED, gi => gi.BulletsFired.ToString()},
//.... etc for all value extractions
};
You can then use this dictionary to extract the value in your sample method:
public static List<MyResult> GetMyResult(GameInfo[] gameInfos, int input)
{
return gameInfo.Select(gi => new MyResult()
{
UserId = gi.UserId,
ResultValue = valueExtractors[input](gi)
}).ToList<MyResult>();
}
Outside of this option, you could potentially have some sort of file/database/stored lookup with the number and the property name, then use reflection to extract the value, but that would obviously not perform as well.

I think this code is getting out of hand a bit. You're effectively using constants to index properties - and this is creating fragile code that you're looking to use some technique - such as - reflection, dictionaries, etc - to control the increased complexity.
Effectively the approach that you're using now will end up with code like this:
var results = GetMyResult(gameInfos, BULLETS_FIRED);
The alternative is to define an extension method that lets you do this:
var results = gameInfos.ToMyResults(gi => gi.BulletsFired);
This is strongly-typed, it doesn't require constants, switch statements, reflection, or anything arcane.
Just write these extension methods and you're done:
public static class GameInfoEx
{
public static IEnumerable<MyResult> ToMyResults(
this IEnumerable<GameInfo> gameInfos,
Func<GameInfo, object> selector)
{
return gameInfos.Select(gi => gi.ToMyResult(selector));
}
public static MyResult ToMyResult(
this GameInfo gameInfo,
Func<GameInfo, object> selector)
{
return new MyResult()
{
UserId = gameInfo.UserId,
ResultValue = selector(gameInfo).ToString()
};
}
}
Does that work for you?

You can use reflection for theses purposes. You can implement custom attributes, mark your properties, etc. Also, it is dynamic way to get info about your class if it changes.

If you want to manage switch code I would point you at Design Patterns book (GoF) and suggest possibly looking at patterns like Strategy and possibly Factory (thats when we talk about general case use, your case isn't very suited for Factory) and implementing them.
While switch statement still has to be left somewhere after refactoring to pattern is complete (for example, in a place where you select strategy by id), code will be much more maintanable and clear.
That said about general switch maintenance, if they become beast like, I am not sure its best solution given how similar your case statements look.
I am 100% sure you can create some method (possibly an extension method) that will be accepting desired property accessor lambda, that should be used when results are generated.

If you want your code to be more generic, I agree with the suggestion of a dictionary or some kind of lookup pattern.
You could store functions in the dictionary, but they seemly all perform the same operation - getting the value from a property. This is ripe for reflection.
I'd store all your properties in a dictionary with an enum (prefer an enum to a const) as the key, and a PropertyInfo - or, less preferred, a string which describes the name of the property - as the value. You then call the GetValue() method on the PropertyInfo object to retrieve the value from the object / class.
Here's an example where I'm mapping enum values to their 'same named' properties in a class, and then using reflection to retrieve the values out of a class.
public enum Properties
{
A,
B
}
public class Test
{
public string A { get; set; }
public int B { get; set; }
}
static void Main()
{
var test = new Test() { A = "A value", B = 100 };
var lookup = new Dictionary<Properties, System.Reflection.PropertyInfo>();
var properties = typeof(Test).GetProperties().ToList();
foreach (var property in properties)
{
Properties propertyKey;
if (Enum.TryParse(property.Name, out propertyKey))
{
lookup.Add(propertyKey, property);
}
}
Console.WriteLine("A is " + lookup[Properties.A].GetValue(test, null));
Console.WriteLine("B is " + lookup[Properties.B].GetValue(test, null));
}
You can map your const values to the names of the properties, PropertyInfo objects which relate to those properties, functions which will retrieve the property values... whatever you think suits your needs.
Of course you will need some mapping - somewhere along the way you will be depending on your input value (the const) mapping to a specific property. The method by which you can get this data might determine the best mapping structure and pattern for you.

I think the way to go is indeed some kind of mapping from one value (int) to something that is somehow a function that knows how to extract a value.
If you really want to keep it extensible, so that you can easily add some without touching the code, and possibly accessing more complex properties (ie. nested properties, do some basic computation), you may want to keep that in a separate source.
I think one way to do this is to rely on the Scripting Services, for instance evaluating a simple IronPython expression to extract a value...
For instance in a file you could store something like :
<GameStats>
<GameStat name="MatchesWon" id="1">
<Expression>
currentGameInfo.BulletsFired.ToString()
</Expression>
</GameStat>
<GameStat name="FancyStat" id="2">
<Expression>
currentGameInfo.SuperCoolNestedGameInfo.NestedIntValue.ToString()
</Expression>
</GameStat>
</GameStats>
and then, depending on the requested stat, you always end up retrieving the general GameInfos. You can them have some kind of foreach loop with :
foreach( var gameInfo in gameInfos){
var currentGameInfo = gameInfo
//evaluate the expression for this currentGameInfo
return yield resultOfEvaluation
}
See http://www.voidspace.org.uk/ironpython/dlr_hosting.shtml for examples on how to embed IronPython Scripting in a .NET application.
NOTE: when working with this kind of stuff, there are several things you must really be careful about:
this potentially allows someone to inject code in your application ...
you should measure the performance impact of Dynamic evaluation in here

I don't have a solution to your switch problem off the top of my head, but you could certainly reduce the code by using a class that can automatically map all the fields you need. Check out http://automapper.org/.

I would not have written the GetMyResult method in the first place. All it is doing is transforming GameInfo sequence into MyResult sequence. Doing it with Linq would be easier and more expressive.
Instead of calling
var myResultSequence = GetMyResult(gameInfo, MatchesWon);
I would simply call
var myResultSequence = gameInfo.Select(x => new MyResult() {
UserId = x.UserId,
ResultValue = x.MatchesWon.ToString()
});
To make it more succinct you can pass the UserId and ResultValue in constructor
var myResultSequence =
gameInfo.Select(x => new MyResult(x.UserId, x.MatchesWon.ToString()));
Refactor only if you see the selects getting duplicated too much.

This is one possible way without using reflection:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
public class GameInfo
{
public int UserId { get; set; }
public int MatchesWon { get; set; }
public long BulletsFired { get; set; }
public string LastLevelVisited { get; set; }
// thousands more of these
}
public class MyResult
{
public int UserId { get; set; } // user id from above object
public string ResultValue { get; set; } // one of the value fields from above with .ToString() executed on it
}
public enum DataType
{
MatchesWon = 1,
BulletsFired = 2,
// add more as needed
}
class Program
{
private static Dictionary<DataType, Func<GameInfo, object>> getDataFuncs
= new Dictionary<DataType, Func<GameInfo, object>>
{
{ DataType.MatchesWon, info => info.MatchesWon },
{ DataType.BulletsFired, info => info.BulletsFired },
// add more as needed
};
public static IEnumerable<MyResult> GetMyResult(GameInfo[] gameInfos, DataType input)
{
var getDataFunc = getDataFuncs[input];
return gameInfos.Select(info => new MyResult()
{
UserId = info.UserId,
ResultValue = getDataFunc(info).ToString()
});
}
static void Main(string[] args)
{
var testData = new GameInfo[] {
new GameInfo { UserId="a", BulletsFired = 99, MatchesWon = 2 },
new GameInfo { UserId="b", BulletsFired = 0, MatchesWon = 0 },
};
// you can now easily select whatever data you need, in a type-safe manner
var dataToGet = DataType.MatchesWon;
var results = GetMyResult(testData, dataToGet);
}
}
}

Purely on the question of large switch statements, it is notable that there are 2 variants of the Cyclomatic Complexity metric in common use. The "original" counts each case statement as a branch and so it increments the complexity metric by 1 - which results in a very high value caused by many switches. The "variant" counts the switch statement as a single branch - this is effectively considering it as a sequence of non-branching statements, which is more in keeping with the "understandability" goal of controlling complexity.

How can I refactor this C# code

Basically I have a method that takes an object and sets another objects properties based on the object passed in.
e.g:
private void SetObject(MyClass object)
{
MyClass2 object2 = new MyClass2();
object2.Property1 = HelperClass.Convert(object.Property1);
//....
// Lots more code ....
//....
}
Now the method is 53 lines long because there are alot of properties to set. The method seems too long to me but I'm struggling to work out how I can possibly break it down.
One option is to try and group up similar properties and pass the object around as a reference to different methods that set these similar properties, but that doesn't seem to sit right with me.
Or I could create a constructor for MyClass2 that accepts a MyClass1 but that doesn't seem right either.
Anyway would welcome some suggestions.
EDIT: Ok thanks for the replies I'll have to give more info, the property names arent the same and I have to call some conversion methods as well. Reflection wouldn't be good because of this and also the performance hit. Automapper I think for the same reasons.
A real example of the code:
private ReportType GetReportFromItem(SPWeb web, SPListItem item)
{
ReportType reportType = new ReportType();
reportType.ReportID = int.Parse(item["Report ID"].ToString());
reportType.Name = item["Title"].ToString();
reportType.SourceLocation = FieldHelpers.GetUri(item["Source Location"]);
reportType.TargetLocation = FieldHelpers.GetUri(item["Document Library"]);
SPFieldUserValue group1 =
new SPFieldUserValue(web, FieldHelpers.GetStringFieldValue(item, "Security Group 1"));
reportType.SecurityGroup1 = group1.LookupValue;
SPFieldUserValue group2 =
new SPFieldUserValue(web, FieldHelpers.GetStringFieldValue(item, "Security Group 2"));
reportType.SecurityGroup2 = group2.LookupValue;
SPFieldUserValue group3 =
new SPFieldUserValue(web, FieldHelpers.GetStringFieldValue(item, "Security Group 3"));
reportType.SecurityGroup3 = group3.LookupValue;
SPFieldUserValue group4 =
new SPFieldUserValue(web, FieldHelpers.GetStringFieldValue(item, "Security Group 4"));
// More code
//...
//...
}

Sounds like a job for AutoMapper

use reflection to do it. probably have a method like this:
private void SetProperties<T>(List<T> objects, List<Tuple<string, object>> propsAndValues) where T:<your_class>
{
Type type = typeof(T);
var propInfos = propsAndValues.ToDictionary(key => type.GetProperty(key.Item1, BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance | BindingFlags.SetProperty), elem => elem.Item2);
objects.AsParallel().ForAll(obj =>
{
obj.SetProps(propInfos);
});
}
public static void SetProps<T>(this T obj, Dictionary<PropertyInfo, object> propInfos) where T : <your_class>
{
foreach (var propInfo in propInfos)
{
propInfo.Key.SetValue(obj, propInfo.Value, null);
}
}

There are a few strategies that came to my mind for doing this, all with their own advantages and disadvantages. Also, I was not familiar with it, but the AutoMapper tool linked to in a different answer to your question sounds like it also could be a good solution. (Also, if there were any way of deriving your classes all from the same class, or storing the properties themselves in a struct instead of directly in the classes, those seem like things to consider as well.)
Reflection
This was mentioned in this answer. However, I am not sure I totally understand the intended use of the functions in that answer, since I don't see a GetValue call, nor any mapping between two types. Also, I can see times where you might want to create something to allow for two different names to map to one another, or for conversion between two types. For a rather generic solution, I would probably go with an approach like this:
Create an extension class with one or more methods that will use reflection to copy based on identical property names and/or pre-defined configuration objects.
For each pair of types that has properties that won't have identical names, create a configuration object mapping the names to each other.
For properties that you won't want to be copied, create a configuration object that holds a list of names to ignore.
I don't actually see anything objectionable about passing one class to another in the constructor if the intent is to copy the properties, seems more of a matter of style than anything hard and fast.
Example Code
classes to be copied to:
public class MyClass2
{
public int Property1 { get; set; }
public int Property2 { get; set; }
public string Property3WithOtherName { get; set; }
public double Property4 { get; set; }
public string Property5WithDifferentName { get; set; }
public string TestIntToString { get; set; }
public int TestStringToInt { get; set; }
}
public class MyClass3
{
public int Prop1 { get; set; }
public int Prop2 { get; set; }
public string Prop3OtherName { get; set; }
public double Prop4 { get; set; }
public string Prop5DiffName { get; set; }
public string PropOnlyClass3 { get; set; }
public string[] StringArray { get; set; }
}
class to be copied, w/ mapping info to the other objects:
public class MyClass
{
public int Property1 { get; set; }
public int Property2 { get; set; }
public string Property3 { get; set; }
public double Property4 { get; set; }
public string Property5 { get; set; }
public double PropertyDontCopy { get; set; }
public string PropertyOnlyClass3 { get; set; }
public int[] PropertyIgnoreMe { get; set; }
public string[] StringArray { get; set; }
public int TestIntToString { get; set; }
public string TestStringToInt { get; set; }
# region Static Property Mapping Information
// this is one possibility for creating and storing the mapping
// information: the class uses two dictionaries, one that links
// the other type with a dictionary of mapped properties, and
// one that links the other type with a list of excluded ones.
public static Dictionary<Type, Dictionary<string, string>>
PropertyMappings =
new Dictionary<Type, Dictionary<string, string>>
{
{
typeof(MyClass2),
new Dictionary<string, string>
{
{ "Property3", "Property3WithOtherName" },
{ "Property5", "Property5WithDifferentName" },
}
},
{
typeof(MyClass3),
new Dictionary<string, string>
{
{ "Property1", "Prop1" },
{ "Property2", "Prop2" },
{ "Property3", "Prop3OtherName" },
{ "Property4", "Prop4" },
{ "Property5", "Prop5DiffName" },
{ "PropertyOnlyClass3", "PropOnlyClass3" },
}
},
};
public static Dictionary<Type, List<string>>
UnmappedProperties =
new Dictionary<Type, List<string>>
{
{
typeof(MyClass2),
new List<string>
{
"PropertyDontCopy",
"PropertyOnlyClass3",
"PropertyIgnoreMe"
}
},
{
typeof(MyClass3),
new List<string>
{
"PropertyDontCopy",
"PropertyIgnoreMe"
}
}
};
// this function pulls together an individual property mapping
public static Tuple<Dictionary<string, string>, List<string>>
MapInfo<TOtherType>()
{
return
new Tuple<Dictionary<string,string>,List<string>>
(
PropertyMappings[typeof(TOtherType)],
UnmappedProperties[typeof(TOtherType)]
);
}
#endregion
}
Mapping Extension Class:
public static class MappingExtensions
{
// this is one possibility for setting up object mappings
#region Type Map Definition Section
// * set up the MapInfo<TOther>() call in each object to map
// * setup as follows to map two types to an actual map
public static Tuple<Type, Type> MapFromTo<TFromType, TToType>()
{
return Tuple.Create<Type,Type>(typeof(TFromType), typeof(TToType));
}
static Dictionary<
Tuple<Type, Type>,
Tuple<Dictionary<string, string>, List<string>>
>
MappingDefinitions =
new Dictionary <
Tuple<Type,Type>,
Tuple<Dictionary<string,string>,List<string>>
>
{
{ MapFromTo<MyClass,MyClass2>(), MyClass.MapInfo<MyClass2>() },
{ MapFromTo<MyClass,MyClass3>(), MyClass.MapInfo<MyClass3>() },
};
#endregion
// method using Reflection.GetPropertyInfo and mapping info to do copying
// * for fields you will need to reflect using GetFieldInfo() instead
// * for both you will need to reflect using GetMemberInfo() instead
public static void CopyFrom<TFromType, TToType>(
this TToType parThis,
TFromType parObjectToCopy
)
{
var Map = MappingDefinitions[MapFromTo<TFromType, TToType>()];
Dictionary<string,string> MappedNames = Map.Item1;
List<string> ExcludedNames = Map.Item2;
Type FromType = typeof(TFromType); Type ToType = typeof(TToType);
// ------------------------------------------------------------------------
// Step 1: Collect PIs for TToType and TFromType for Copying
// ------------------------------------------------------------------------
// Get PropertyInfos for TToType
// the desired property types to reflect for ToType
var ToBindings =
BindingFlags.Public | BindingFlags.NonPublic // property visibility
| BindingFlags.Instance // instance properties
| BindingFlags.SetProperty; // sets for ToType
// reflect an array of all properties for this type
var ToPIs = ToType.GetProperties(ToBindings);
// checks for mapped properties or exclusions not defined for the class
#if DEBUG
var MapErrors =
from name in
MappedNames.Values
where !ToPIs.Any(pi => pi.Name == name)
select string.Format(
"CopyFrom<{0},{1}>: mapped property '{2}' not defined for {1}",
FromType.Name, ToType.Name, name
);
#endif
// ------------------------------------------------------------------------
// Get PropertyInfos for TFromType
// the desired property types to reflect; if you want to use fields, too,
// you can do GetMemberInfo instead of GetPropertyInfo below
var FromBindings =
BindingFlags.Public | BindingFlags.NonPublic // property visibility
| BindingFlags.Instance // instance/static
| BindingFlags.GetProperty; // gets for FromType
// reflect all properties from the FromType
var FromPIs = FromType.GetProperties(FromBindings);
// checks for mapped properties or exclusions not defined for the class
#if DEBUG
MapErrors = MapErrors.Concat(
from mn in MappedNames.Keys.Concat(
ExcludedNames)
where !FromPIs.Any(pi => pi.Name == mn)
select string.Format(
"CopyFrom<{0},{1}>: mapped property '{2}' not defined for {1}",
FromType.Name, ToType.Name, mn
)
);
// if there were any errors, aggregate and throw
if (MapErrors.Count() > 0)
throw new Exception(
MapErrors.Aggregate(
"", (a,b)=>string.Format("{0}{1}{2}",a,Environment.NewLine,b)
));
#endif
// exclude anything in the exclusions or not in the ToPIs
FromPIs = FromPIs.Where(
fromPI =>
!ExcludedNames.Contains(fromPI.Name)
&& ToPIs.Select(toPI => toPI.Name).Concat(MappedNames.Keys)
.Contains(fromPI.Name)
)
.ToArray();
// Step 1 Complete
// ------------------------------------------------------------------------
// ------------------------------------------------------------------------
// Step 2: Copy Property Values from Source to Destination
#if DEBUG
Console.WriteLine("Copying " + FromType.Name + " to " + ToType.Name);
#endif
// we're using FromPIs to drive the loop because we've already elimiated
// all items that don't have a matching value in ToPIs
foreach (PropertyInfo FromPI in FromPIs)
{
PropertyInfo ToPI;
// if the 'from' property name exists in the mapping, use the mapped
// name to find ToPI, otherwise use ToPI matching the 'from' name
if (MappedNames.Keys.Contains(FromPI.Name))
ToPI = ToPIs.First(pi => pi.Name == MappedNames[FromPI.Name]);
else
ToPI = ToPIs.First(pi => pi.Name == FromPI.Name);
Type FromPropertyType = FromPI.PropertyType;
Type ToPropertyType = ToPI.PropertyType;
// retrieve the property value from the object we're copying from; keep
// in mind if this copies by-reference for arrays and other ref types,
// so you will need to deal with it if you want other behavior
object PropertyValue = FromPI.GetValue(parObjectToCopy, null);
// only need this if there are properties with incompatible types
// * implement IConvertible for user-defined types to allow conversion
// * you can try/catch if you want to ignore items which don't convert
if (!ToPropertyType.IsAssignableFrom(FromPropertyType))
PropertyValue = Convert.ChangeType(PropertyValue, ToPropertyType);
// set the property value on the object we're copying to
ToPI.SetValue(parThis, PropertyValue, null);
#if DEBUG
Console.WriteLine(
"\t"
+ "(" + ToPI.PropertyType.Name + ")" + ToPI.Name
+ " := "
+ "(" + FromPI.PropertyType.Name + ")" + FromPI.Name
+ " == "
+ ((ToPI.PropertyType.Name == "String") ? "'" : "")
+ PropertyValue.ToString()
+ ((ToPI.PropertyType.Name == "String") ? "'" : "")
);
#endif
}
// Step 2 Complete
// ------------------------------------------------------------------------
}
}
Test Method:
public void RunTest()
{
MyClass Test1 = new MyClass();
Test1.Property1 = 1;
Test1.Property2 = 2;
Test1.Property3 = "Property3String";
Test1.Property4 = 4.0;
Test1.Property5 = "Property5String";
Test1.PropertyDontCopy = 100.0;
Test1.PropertyIgnoreMe = new int[] { 0, 1, 2, 3 };
Test1.PropertyOnlyClass3 = "Class3OnlyString";
Test1.StringArray = new string[] { "String0", "String1", "String2" };
Test1.TestIntToString = 123456;
Test1.TestStringToInt = "654321";
Console.WriteLine("-------------------------------------");
Console.WriteLine("Copying: Test1 to Test2");
Console.WriteLine("-------------------------------------");
MyClass2 Test2 = new MyClass2();
Test2.CopyFrom(Test1);
Console.WriteLine("-------------------------------------");
Console.WriteLine("Copying: Test1 to Test3");
Console.WriteLine("-------------------------------------");
MyClass3 Test3 = new MyClass3();
Test3.CopyFrom(Test1);
Console.WriteLine("-------------------------------------");
Console.WriteLine("Done");
Console.WriteLine("-------------------------------------");
}
}
Output:
-------------------------------------
Copying: Test1 to Test2
-------------------------------------
Copying MyClass to MyClass2
(Int32)Property1 := (Int32)Property1 == 1
(Int32)Property2 := (Int32)Property2 == 2
(String)Property3WithOtherName := (String)Property3 == 'Property3String'
(Double)Property4 := (Double)Property4 == 4
(String)Property5WithDifferentName := (String)Property5 == 'Property5String'
(String)TestIntToString := (Int32)TestIntToString == '123456'
(Int32)TestStringToInt := (String)TestStringToInt == 654321
-------------------------------------
Copying: Test1 to Test3
-------------------------------------
Copying MyClass to MyClass3
(Int32)Prop1 := (Int32)Property1 == 1
(Int32)Prop2 := (Int32)Property2 == 2
(String)Prop3OtherName := (String)Property3 == 'Property3String'
(Double)Prop4 := (Double)Property4 == 4
(String)Prop5DiffName := (String)Property5 == 'Property5String'
(String)PropOnlyClass3 := (String)PropertyOnlyClass3 == 'Class3OnlyString'
(String[])StringArray := (String[])StringArray == System.String[]
-------------------------------------
Done
-------------------------------------
NOTE: if you have use for copying back the other direction, or would like, for instance, to create your mappings with a code generator, you may want to go with having your mappings in a separate static variable somewhere else, mapped by both types, rather than storing your mappings directly within a class. If you want to reverse direction, you could probably just add a flag to the existing code that lets you invert the meanings of the tables and of the passed types, although I would recommend changing references to TToType and TFromType to TType1 and TType2.
For having a code generator generate the mapping it's probably a good bit easier to separate it into the separate class with two type parameters for the generic, so that you don't necessarily have to worry about putting those definitions directly within your classes; I was torn about how to do it when I wrote the code, but I do think that would probably have been a more flexible option. (On the other hand, it probably means needing larger overall structure, which is why I broke it out like I did in the first place.) Another advantage to this way is that you don't necessarily need to create everything all at once, you could conceivable change to member variables that let you create them on-the-fly as needed, possibly through a function param or through an additional interface on your object.
Code Generation
This can be used by itself, it can also be used as a tool in conjunction with either of the next two methods. But the idea is that you can create a CSV or use some other method to hold your mapping data, and then you can create class templates (in separate files or in code) with placeholders in them (e.g., ${PROPERTIES_LIST}) that you can use to do .Replace() operations on, or you can create templates of the .xsd files used for typed dataset generation in the next section, generate the individual lines of the .xsd from the list, or, finally you could create the structures that hold the mapping information for something like the solution I give in the reflection section.
One thing I've done in the past which was very handy was to just whip up a typed dataset with a table structure that can hold all the information I need to do my code generation, and use the old .NET 2.0 version of the GridView to allow me to enter the data in. But even with just a simple XmlDocument or CSV file(s), it should be very easy to enter your properties mappings and read them back in, and the none of the generation for any of the scenarios here is likely to be terribly much effort, usually even compared to having to type it all in by hand just once or twice, plus if it's something that gets updated at all often, you will eventually save yourself hand-coding errors and debug time as well.
Typed Data Sets
Although it's sort of beyond the intended use of the data set, if you don't need super-high performance, it can come in handy. After defining a table in the dataset and building, you have a set of strongly-typed objects that can be used, for instance, to hold objects representing the tables and columns or rows. So, you could easily create a typed dataset from scratch using column names and types matching your objects, and then loop through the column names to get the names of your properties. While not as powerful as reflection, it could be a very quick way of getting yourself set up to copy two objects with the same property names. Of course, it's a much more limited usefulness because it's only going to be useful if you have control over your types, and if you don't have any particularly complicated needs for copying the data.
But it also can let you do things like:
MyClassDataRow Object1 = MyDataSet.MyClassTable.NewRow();
Object1.Prop1 = 123;
Object2.Prop2 = "Hello Dataset";
// etc...
MyClass2DataRow Object2 = MyDataSet.MyClass2Table.NewRow();
foreach (DataColumn ColumnName in MyClassTable.Columns)
Object2[ColumnName] = Object1[ColumnName];
with little additional effort. And, if you're in a situation where you want to be able save your objects out to disk, just add the rows to the table you've got a great way of serializing the data with the DataSet.ReadXml and DataSet.WriteXml calls.
Also, for the reflection solution, as long as your requirements weren't too complicated, you could create your mapping definitions by creating a typed dataset with a couple of tables with column names matching those to map, and then using the information in the DataColumns of the tables to do your mapping definition instead of Dictionaries, Lists, and Tuples. Using some sort of predefined names prefixes or otherwise unused types in your table, you ought to be able to duplicate most of the functionality in the sample code.