GRIDVIEW删除问题(请高手指教)

有个数据表aa,结构如下:id(int)主键,account(nvarchar(64)),dtime(datetime)
数据集里有个DeleteQuery(DELETE FROM aa WHERE (ID = @Original_ID))
gridview帮定只帮定了account和dtime,在删除按纽处代码        DMDataSetTableAdapters.competition_continueTableAdapter otaAdapter = new DMDataSetTableAdapters.competition_continueTableAdapter();
otaAdapter.DeleteQuery(Convert.ToInt32(GridView1.DataKeys[i][0]));
排错提示:确保方法的参数格式正确,将一个字符串转换为DateTime,先分析字符串获取日期,然后将每个变量放置到DateTime对象中
如果我把DeleteQuery(DELETE FROM aa WHERE (ID = @Original_ID))该成DeleteQuery(DELETE FROM aa WHERE (account = @Original_account)).
otaAdapter.DeleteQuery(Convert.ToInt32(GridView1.DataKeys[i][0]))改成otaAdapter.DeleteQuery(Convert.ToString(GridView1.DataKeys[i][0]));
删除就没问题.请问这是怎么回事?