edit form 的非空驗證

protected void RadGrid4_ItemDataBound(object sender, GridItemEventArgs e)
    {
        if ((e.Item is GridEditableItem) && (e.Item.IsInEditMode))
        {
            var editForm = (GridEditableItem)e.Item;
            var update = (LinkButton)editForm.FindControl("UpdateButton");
            var insert = (LinkButton)editForm.FindControl("PerformInsertButton");
            var txtbx = (TextBox)editForm["taskName"].Controls[0];
            if (update != null)
            {
                update.Attributes.Add("onclick", "return Validate('" + txtbx.ClientID + "')");
            }
            if (insert != null)
            {
                insert.Attributes.Add("onclick", "return Validate('" + txtbx.ClientID + "')");
            }
        }
    }