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 请看下面，下面是怎么会事？

在下面的中DropDownList1上绑定了数据。

protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType ==DataControlRowType.DataRow)
        {
            DataSet Ds = new DataSet();
            DropDownList ddl = (DropDownList)e.Row.FindControl("DropDownList1");
            string Name = "GetBooks";//存储过程名字
            int strWhere = 0;//表示查询条件为空

            //访问类库的Sql静态方法
            Ds = DB.GetList(Name, strWhere);
            if (Ds.Tables[0].Rows.Count != 0)
            {
                ///绑定数据
                ddl.DataSource = Ds;
                ddl.DataTextField = "AuthorName";
                ddl.DataValueField = "AuthorName";
            }

        //    Button btnDel = (Button)e.Row.FindControl("btndel");
        //    btnDel.Attributes.Add("onclick", "return confirm('真的要删除吗？')");
        }
    }

在下面的中DropDownList1上绑定不了数据。

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            ////DataSet Ds = new DataSet();
            ////DropDownList ddl = (DropDownList)e.Row.FindControl("DropDownList1");
            ////string Name = "GetBooks";//存储过程名字
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