SharePointConnectionException when executing a SharePoint command

The other day I developed a custom SharePoint command in Visual Studio 2010.

I was to specify a String parameter for the command and it should have returned a simple .NET object having a few properties. Something like that:

1. using System;
2.  
3. namespace MyNameSpace
4. {
5.     public class MyClass
6.     {
7.         public String Title { get; set; }
8.         public bool IsDeleted { get; set; }
9.     }
10. }

To execute the command that returns this kind of data I had to use the following overload of the ExecuteCommand method:

TResult ExecuteCommand<T, TResult>(string commandId, T arg)

It seemed that the command was executed successfully, but I experienced that instead of the expected result, an exotic runtime exception was generated:

Microsoft.VisualStudio.SharePoint.SharePointConnectionException. Message: Type ‘MyNameSpace.MyClass’ with data contract name ‘MyClass:http://schemas.datacontract.org/2004/07/SPVSCommands’ is not expected. 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.

I used this type of ExecuteMethod successfully for simple object types, like String.

The following posts gave me some info on the possible background of the error:

All About KnownTypes
About KnownTypeAttribute example

Finally, I found a rather simple and logic solution for the issue:

1. using System;
2. using System.Runtime.Serialization;
3.  
4. namespace MyNameSpace
5. {
6.     [Serializable()]
7.     public class MyClass
8.     {
9.         public String Title { get; set; }
10.         public bool IsDeleted { get; set; }
11.     }
12. }

It seems the object must be serializable to be transmitted over the wire. It is interesting that if I use a similar “complex” object type as the input parameter of the ExecuteMethod, it runs without error, even if the class is not serializable.

Tags: SP 2010, VSX