删除前的判断。

procedure TForm1.Button8Click(Sender: TObject);
var
SQLL:string;
begin
    if  DBGridEh2.DataSource.DataSet=nil then
    begin
     showmessage('没有可删除数据！');
    end
     else
    begin
    SQLL:='delete from Checke where Dormitory='''+DBGridEh2.Columns.Grid.Fields[0].Value+'''';

      if application.MessageBox('是否要删除此信息！','提示',mb_yesno)=idyes then
         begin
           with ADOQuery1 do
            begin
             Close;
             SQL.Clear;
             SQL.Add('select * from Dormitory where Dormitory= '''+DBGridEh2.Columns.Grid.Fields[0].Value+'''');
             Open;
            end;
             if ADOQuery1.RecordCount>0 then
              begin
                showmessage('操作失败！');
                exit;
              end
              else
              begin
                Form1.shuaixi(DBGridEh2,DBGridEh1,DBGridEh3,DBGridEh4);
              end;
         end;
    end;
end;