Hi.
I saw your code what you have tried so far, there is nothing wrong in that but I am not sure stored procedure of
GetAllUsers
as
Karthik told, Can you share your stored procedure here. so that we can help you find the solution.
You can call this code for binding data from List
List<Users> usersList=userDB.GetAllUsers();
GridView1.DataSource = usersList;
GridView1.DataBind();