I tried using a <data:EntityGridView DataSource='<%# Eval("MyDetailsTableCollection") %>' ...
Throws an "Object reference not set to an instance of an object."
On line 242 in EntityGridView.cs
DataSourceControl dsc = (DataSourceControl)this.Parent.FindControl(string.Format("{0}", this.DataSourceID));
System.Reflection.EventInfo eventInfo = dsc.GetType().GetEvent("Selected");
I noticed that since this.DataSourceID is null... resulting in dsc is null...
Causes the next line of code "dsc.GetType()" to throw the exception.