Your Where clause is wrong in your stored procedure. Should be:
ALTER PROCEDURE [dbo].[sproc_del_MenuItem]
@MenuID int
AS
BEGIN
DELETE FROM CampRandolph.dbo.Menu
WHERE MenuID = @MenuID
END
In your definition of the GridView add DataKeyNames property:
<asp:GridView ID="GridView1" runat="server" DataKeyNames="MenuID" ....
I also read that the HeaderText needs to be the same as key name:
<asp:BoundField DataField="MenuID" HeaderText="MenuID" Visible="true" ReadOnly="true" />