Question

我似乎无法弄清楚为什么这不起作用... 我有两个下拉列表。第一个我绑定到DataView 第二个我想将其绑定到DataTable本身。
当我尝试使用block将第二个下拉列表绑定到DataView之外的数据表时。我没有填充记录...

不确定为什么会这样..有人有什么想法吗？如果我移动代码以将第二个下拉列表绑定到DataView的using块内或该块之前，则可以正常工作。

为什么我不能在使用块的DataView之外使用DataTable？

下面是我的代码：

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolderBody" runat="Server">    
    <asp:DropDownList runat="server" ID="ddlEstNo1"></asp:DropDownList>    
    <asp:DropDownList runat="server" ID="ddlEstNo2"></asp:DropDownList>
</asp:Content>


protected void bindDDLs(string vCat, int year, int month)
{
    using (DataTable dt = getData(vCat, year, month))
    {

        // THIS CODE ALSO WORKS..
        //ddlEstNo2.DataSource = dt;
        //ddlEstNo2.DataTextField = "estNo";
        //ddlEstNo2.DataValueField = "estNo";
        //ddlEstNo2.DataBind();
        //ddlEstNo2.Items.Insert(0, new ListItem("--Any--", ""));
        //ddlEstNo2.Items.Remove("Summary");

        using (DataView dv = dt.DefaultView)
        {
            // populate ddlEstNo1
            ddlEstNo1.DataSource = dv;
            ddlEstNo1.DataTextField = "estNo";
            ddlEstNo1.DataValueField = "estNo";
            ddlEstNo1.DataBind();
            ddlEstNo1.Items.Insert(0, new ListItem("--Any--", ""));
            ddlEstNo1.Items.Remove("Summary");

            // THIS CODE ALSO WORKS..
            //ddlEstNo2.DataSource = dt;
            //ddlEstNo2.DataTextField = "estNo";
            //ddlEstNo2.DataValueField = "estNo";
            //ddlEstNo2.DataBind();
            //ddlEstNo2.Items.Insert(0, new ListItem("--Any--", ""));
            //ddlEstNo2.Items.Remove("Summary");
        }

        // populate ddlEstNo2 ==>>> doesnt work!
        ddlEstNo2.DataSource = dt;
        ddlEstNo2.DataTextField = "estNo";
        ddlEstNo2.DataValueField = "estNo";
        ddlEstNo2.DataBind();
        ddlEstNo2.Items.Insert(0, new ListItem("--Any--", ""));
        ddlEstNo2.Items.Remove("Summary");

    }
}

Answer 1

实际上您的第二个using语句以某种方式取消了第一个using语句的作用……所以您可以做的是

     using (DataTable dt = getData(vCat, year, month))
  using (DataView dv = dt.DefaultView)
        {

            // THIS CODE ALSO WORKS..
            //ddlEstNo2.DataSource = dt;
            //ddlEstNo2.DataTextField = "estNo";
            //ddlEstNo2.DataValueField = "estNo";
            //ddlEstNo2.DataBind();
            //ddlEstNo2.Items.Insert(0, new ListItem("--Any--", ""));
            //ddlEstNo2.Items.Remove("Summary");



                // populate ddlEstNo1
                ddlEstNo1.DataSource = dv;
                ddlEstNo1.DataTextField = "estNo";
                ddlEstNo1.DataValueField = "estNo";
                ddlEstNo1.DataBind();
                ddlEstNo1.Items.Insert(0, new ListItem("--Any--", ""));
                ddlEstNo1.Items.Remove("Summary");

                // THIS CODE ALSO WORKS..
                //ddlEstNo2.DataSource = dt;
                //ddlEstNo2.DataTextField = "estNo";
                //ddlEstNo2.DataValueField = "estNo";
                //ddlEstNo2.DataBind();
                //ddlEstNo2.Items.Insert(0, new ListItem("--Any--", ""));
                //ddlEstNo2.Items.Remove("Summary");


            // populate ddlEstNo2 ==>>> doesnt work!
            ddlEstNo2.DataSource = dt;
            ddlEstNo2.DataTextField = "estNo";
            ddlEstNo2.DataValueField = "estNo";
            ddlEstNo2.DataBind();
            ddlEstNo2.Items.Insert(0, new ListItem("--Any--", ""));
            ddlEstNo2.Items.Remove("Summary");

        }

使用（DataView dv = dt.DefaultView）块后，下拉列表数据绑定不起作用

1 个答案: