C# windows application binding a gridview

Question

In my application I have 2 datatables. One is NameTable (Id,Name), other is FriendsTable(NameId,Name). NameId of FriendsTable is the Id of NameTable. Now in my application I want to display data in gridview as follows: Gridview should show NameTable rows i.e. Id and Name and also displays count of Friends. So gridview must contain 3 columns, 2 displaying NameTable columns and third the count. When I double click a row of datagridview, the application must open other window which displays all the Friends in a table. I am stucked in first part of displaying the count column. Please help. Thanks in advance.