Data contract serialization for IList<T>

Question

I have the following code in which I'm trying to serialize a list to a file

public static void Serialize<T>(this IList<T> list, string fileName)  
{
   try
   {
      var ds = new DataContractSerializer(typeof(T));
      using (Stream s = File.Create(fileName))
          ds.WriteObject(s, list);  
   }
   catch (Exception e)
   {
      _logger.Error(e);
      throw;
   } 
}

and I'm getting the exception:

Type 'System.Collections.Generic.List`1[[MyClass, MyNameSpace, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' with data contract name 'ArrayOf*MyClass*:http://schemas.datacontract.org/2004/07/MyNameSpace' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.

[KnownType(typeof(MyClass))]
[DataContract]
public class MyClass
{
    #region Properties
    [DataMember]
    public string Foo{ set; get; }
    [DataMember]
    public string Bar{ set; get; }
}

Any ideas?

There is no inheritance.

shouldn't you be doing new DataContractSerializer(typeof(List<T>)) or something similar — Darren Kopp
good catch. can u write that as response so i can mark it. Thanks, — DarthVader

Darren Kopp Darren Kopp · Accepted Answer · 2011-09-27T17:21:46

What has happened is that the serializer is expecting an instance of T, not a list of T, so you want your method to be like so:

public static void Serialize<T>(this IList<T> list, string fileName)  
{
   try
   {
      var ds = new DataContractSerializer(list.GetType());
      using (Stream s = File.Create(fileName))
        ds.WriteObject(s, list);  
   }
   catch (Exception e)
   {
     _logger.Error(e);
     throw;
   } 
}

Data contract serialization for IList<T>

3 Answers