RadGrid Row Select

If you want to select row in RadGrid then set some RadGrid properties like 

            <ClientSettings Selecting-AllowRowSelect="true" Selecting-EnableDragToSelectRows="false">
             <MasterTableView DataKeyNames="ID">



If you want to select first row then use below code

               if (RadGrid.Items.Count > 0)
                {
                    RadGrid.MasterTableView.Items[0].Selected = true;
                }

If you want to select any row on that basis of data key name then use below code

              GridDataItem item = RadGrid.MasterTableView.FindItemByKeyValue("ID", "4");
                if (item != null)
                {
                    item.Selected = true;
                }