在EditItemTemplate中对DropDownList进行数据绑定

DataList和GridView等数据绑定控件给我们提供了一个非常实用的功能:只需编写很少的代码就能实现数据的更新和删除。在实现数据的更新时需要使用EditItemTemplate模板,我们常见的EditItemTemplate模板中的代码形如:

<asp:DataList ID="DataList1" runat="server" DataKeyField="ID" OnEditCommand="DataList1_Edit">
    <ItemTemplate>
        <asp:Label ID="Label1" runat="server" Text='<%# Eval("Province") %>'></asp:Label>
        <asp:Button ID="Button1" runat="server" CommandName="edit" Text="编辑" />
    </ItemTemplate>
    <EditItemTemplate>
        <asp:TextBox ID="TextBox1" runat="server" Text='<%# Eval("Province") %>'></asp:TextBox>
    </EditItemTemplate>
</asp:DataList>

注意上边使用的是TextBox,但有时所需更改的数据是某个序列中的一个成员,此时我们就应使用DropDownList控件,如下所示:

<asp:DataList ID="DataList1" runat="server" DataKeyField="ID" OnEditCommand="DataList1_Edit">
    <ItemTemplate>
        <asp:Label ID="Label1" runat="server" Text='<%# Eval("Province") %>'></asp:Label>
        <asp:Button ID="Button1" runat="server" CommandName="edit" Text="编辑" />
    </ItemTemplate>
    <EditItemTemplate>
        <asp:DropDownList ID="DropDownList1" runat="server">
        </asp:DropDownList>
    </EditItemTemplate>
</asp:DataList>

问题随之而来,怎么在点击编辑按钮后对DropDownList1进行数据绑定?这还是比较好解决的,可在DataList1_Edit函数中进行绑定,代码如下:

/// <summary>
/// 编辑
/// </summary>
/// <param name="source"></param>
/// <param name="e"></param>
protected void DataList1_Edit(object source, System.Web.UI.WebControls.DataListCommandEventArgs e)
{
    DataList1.EditItemIndex = e.Item.ItemIndex;
    DataList1_DataBind();

    //对DropDownList1进行数据绑定
    string[] province = { "北京", "上海", "福建" };
    DropDownList MyDropDownList = (DropDownList)DataList1.Items[e.Item.ItemIndex].FindControl("DropDownList1");
    for (int i = 0; i < province.Length; i++)
    {
        MyDropDownList.Items.Add(new ListItem(province[i], province[i]));
    }
}

此外还有一种绑定方法:

<asp:DataList ID="DataList1" runat="server" DataKeyField="ID" OnEditCommand="DataList1_Edit">
    <ItemTemplate>
        <asp:Label ID="Label1" runat="server" Text='<%# Eval("Province") %>'></asp:Label>
        <asp:Button ID="Button1" runat="server" CommandName="edit" Text="编辑" />
    </ItemTemplate>
    <EditItemTemplate>
        <asp:DropDownList ID="DropDownList1" runat="server" DataSource='<%# DropDownList1_DataBind() %>'>
        </asp:DropDownList>
    </EditItemTemplate>
</asp:DataList>

/// <summary>
/// 编辑
/// </summary>
/// <param name="source"></param>
/// <param name="e"></param>
protected void DataList1_Edit(object source, DataListCommandEventArgs e)
{
    DataList1.EditItemIndex = e.Item.ItemIndex;
    DataList1_DataBind();
}

/// <summary>
/// DropDownList1数据绑定
/// </summary>
protected string[] DropDownList1_DataBind()
{
    string[] province = { "北京", "上海", "福建" };
    return province;
}

数据绑定问题是解决了,但新的问题又随之而来:怎么让原先的值处于选中状态?不然给编辑造成了一定的不便!要解决这个问题,就先得想办法获取到原先的值,尝试了多种方法都无法直接获取,最终,在EditItemTemplate放个隐藏的表单来解决:

<asp:DataList ID="DataList1" runat="server" DataKeyField="ID" OnEditCommand="DataList1_Edit">
    <ItemTemplate>
        <asp:Label ID="Label1" runat="server" Text='<%# Eval("Province") %>'></asp:Label>
        <asp:Button ID="Button1" runat="server" CommandName="edit" Text="编辑" />
    </ItemTemplate>
    <EditItemTemplate>
        <asp:TextBox ID="TextBox1" runat="server" Text='<%# Eval("Province") %>' Visible="false"></asp:TextBox>
        <asp:DropDownList ID="DropDownList1" runat="server">
        </asp:DropDownList>
    </EditItemTemplate>
</asp:DataList>

/// <summary>
/// 编辑
/// </summary>
/// <param name="source"></param>
/// <param name="e"></param>
protected void DataList1_Edit(object source, System.Web.UI.WebControls.DataListCommandEventArgs e)
{
    DataList1.EditItemIndex = e.Item.ItemIndex;
    DataList1_DataBind();

    //对DropDownList1进行数据绑定
    string oldProvince = ((TextBox)DataList1.Items[e.Item.ItemIndex].FindControl("TextBox1")).Text;
    string[] province = { "北京", "上海", "福建" };
    DropDownList MyDropDownList = (DropDownList)DataList1.Items[e.Item.ItemIndex].FindControl("DropDownList1");
    for (int i = 0; i < province.Length; i++)
    {
        MyDropDownList.Items.Add(new ListItem(province[i], province[i]));
        if (MyDropDownList.Items[MyDropDownList.Items.Count - 1].Value == oldProvince)
        {
            MyDropDownList.SelectedIndex = MyDropDownList.Items.Count - 1;
        }
    }
}


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