There is a problem with the UltraWebGrid to handle the ExtensionDataObject that I receive from my Service that is implemented with WCF.

Error  I received is
Type 'System.Runtime.Serialization.ExtensionDataObject' in Assembly 'System.Runtime.Serialization, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.

When running the same code with a standard GridView it is not a problem. I retrieve my List<User> and set the grids datasource like this:

this.UltraWebGrid1.DataSource = UserList;
this.UltraWebGrid1.DataBind();

Currently I m in a process of vender evaluation and using a trial-version of infragistics.