如何从代码隐藏更新 DropDownList 的 SQLDataSource

Question

我有两个下拉列表：

<td style="width: 20%;">
    <!-- TASK NAME -->
    <asp:DropDownList ID="ddlTaskName" DataSourceID="dsPopulateTaskName" AutoPostBack="true" DataValueField="Task Name" runat="server" AppendDataBoundItems="true" OnSelectedIndexChanged="ddlTaskName_onSelectIndexChanged">
        <asp:ListItem Text="All" Value="%"></asp:ListItem>
    </asp:DropDownList>
    <asp:SqlDataSource ID="dsPopulateTaskName" runat="server" ConnectionString="<%$ ConnectionStrings:gc %>" SelectCommand=""></asp:SqlDataSource>
</td>
<td style="width: 20%;">
    <!-- SERVICE -->
    <asp:DropDownList ID="ddlService" DataSourceID="dsPopulateService" AutoPostBack="true" DataValueField="Service" runat="server" AppendDataBoundItems="true" OnSelectedIndexChanged="ddlService_onSelectIndexChanged">
        <asp:ListItem Text="All" Value="%"></asp:ListItem>
    </asp:DropDownList>
    <asp:SqlDataSource ID="dsPopulateService" runat="server" ConnectionString="<%$ ConnectionStrings:gc %>" SelectCommand=""></asp:SqlDataSource>
</td>

Page_Load 上的代码隐藏：

strForDropDownList = @" FROM [Db].[dbo].[table1] WHERE [stat] = 'A'";
string pol = " AND ";
if (ddlTaskName.SelectedIndex == 0)
{
    pol += " ([tcol] LIKE '%' OR [tcol] IS NULL) AND ";
}
else
{
    pol += " [tcol] = '" + ddlTaskName.SelectedValue.TrimEnd() + "' AND ";
}
if (ddlService.SelectedIndex == 0)
{
    pol += " (scol LIKE '%' OR scol IS NULL) AND ";
}
else
{
    pol += " scol = '" + ddlService.SelectedValue.TrimEnd() + "' AND ";
}
strWhere = pol;
dsPopulateTaskName.SelectCommand = @"SELECT DISTINCT [tcol] 'Task Name'" + strForDropDownList + strWhere;
dsPopulateService.SelectCommand = @"SELECT DISTINCT scol 'Service'" + strForDropDownList + strWhere;

当页面加载时，一切都以 % 开头并正确填充下拉列表。如果我 select 来自 ddlService 下拉列表的选项，dsPopulateTaskName.SelectCommand 会显示正确的查询以重新填充 ddlTaskName 下拉列表，但不会更新它。

请帮我解决一下

Answer 1

你应该在设置 SelectCommand 后调用 ddlService.DataBind() 和 ddlTaskName.DataBind() ，我的意思是如下：

dsPopulateTaskName.SelectCommand = 
@"SELECT DISTINCT [tcol] 'Task Name'" + strForDropDownList + strWhere;
ddlService.DataBind();

dsPopulateService.SelectCommand = 
@"SELECT DISTINCT scol 'Service'" + strForDropDownList + strWhere;
ddlTaskName.DataBind();

希望对您有所帮助

如何从代码隐藏更新 DropDownList 的 SQLDataSource

How to update the SQLDataSource of a DropDownList from code-behind

c#

asp.net

drop-down-menu