Grideview DataKeys in Asp.net Using C# code

GrideviewName.DataKeyNames = new string[] { "pid", "catId" };
OR

mension datakeys in the source code like in the Gridtag
asp:gridview DataKeyNames=pid,catId
In the above we are given datakeys names pid,catId

Get Datakeys values(pid,catId):

GridviewName.DataKeys[e.RowIndex].Values["Pid"]);
GridviewName.DataKeys[e.RowIndex].Values["catId"]);