Populating DataKeyNames when binding Generic List to Gridview

 I have a generic List which is populated with an object which has properties like FirstName, Surname etc.
If I bind a gridview to the list with autocompletecolumns = true, the Gridview displays the data in the List.
The code looks like:
DataAccess da = new DataAccess();
gvUserList.DataSource = da.getUsers(2);
gvUserList.DataBind();
If I were using a SqlDataReader to populate the GridView I would be able to do something like this:

gvUserList.DataSource = myDataReader; gvUserList.DataKeyNames = new string[] { "FirstName", "Surname" }; gvUserList.DataBind(); My question is:
How do I populate the DataKeyNames with the properties (FirstName, Surname) contained in the object that is contained in each element of the Generic List?
Thanks for any help.

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