C# - How To Get Gridview Underlying Datasource

i have gridview in my asp.net web application under framework 3.5. I am binding the gridview with List. Inside the grid there is update and delete functionalities which are running fine. But my save functionality, for which i decided to extract the list back from the datasource and then through loop i will insert the new list to database. But when i tried to get it conventional way it returned me null.

I tried the following ways to retrieve the List back.

1. List<MyClass> list = (List<MyClass>gv.DataSource);

2. List<MyClass> list = gv.DataSource as List<MyClass>;

3. IDataSource idt = (IDataSource)gv.Datasource;

List<MyClass> list = (List<MyClass>)idt;

But no luck, each time i got null.