C# 级联数据绑定<；ajaxtoolkit:combobox>；及<；asp:dropdownlist>；在asp.net中

我有一个

asp.net

搜索表单，其中包括一个

ajaxToolkit组合框

和一个标准的

asp下拉列表

。两个控件都绑定到两个独立的

SqlDatasource

组件

大概是这样的：

<ajaxToolkit:ComboBox
    ID="cbConvenzionato"
    runat="server"
    AutoCompleteMode="SuggestAppend"
    DropDownStyle="DropDownList"
    DataSourceID="sdsConvenzionati"
    DataTextField="nome"
    DataValueField="id"
    AutoPostBack="true"
    OnSelectedIndexChanged="cbConvenzionato_SelectedIndexChanged" />

<asp:DropDownList
    ID="ddlVeicoli"
    DataSourceID="sdsVeicoli"
    DataTextField="targa"
    DataValueField="id"
    runat="server"
    AutoPostBack="true"
    OnSelectedIndexChanged="ddlVeicoli_SelectedIndexChanged"
    AppendDataBoundItems="true">
    <asp:ListItem Text="TUTTI" Value="" Selected="True" />
</asp:DropDownList>

<asp:SqlDataSource
    ID="sdsConvenzionati"
    runat="server"
    ConnectionString="<%$ ConnectionStrings:db %>"
    ProviderName="<%$ ConnectionStrings:db.ProviderName %>"
    SelectCommand="
        SELECT
            id,
            nome
        FROM
            anag_convenzionati
        ORDER BY nome;" />

<asp:SqlDataSource
    ID="sdsVeicoli"
    runat="server"
    EnableCaching="false"
    CancelSelectOnNullParameter="false"
    ConnectionString="<%$ ConnectionStrings:db %>"
    ProviderName="<%$ ConnectionStrings:db.ProviderName %>"
    SelectCommand="
        SELECT 
            id, 
            targa
        FROM 
            veicoli_contratti
        WHERE
            ((@id_convenzionato IS NULL) OR (id_convenzionato = @id_convenzionato))
        ORDER BY targa;">
    <SelectParameters>
        <asp:ControlParameter
            Name="id_convenzionato"
            ControlID="cbConvenzionato"
            PropertyName="SelectedValue"
            Direction="Input"
            ConvertEmptyStringToNull="true"
            DbType="Int32"
            DefaultValue="" />
    </SelectParameters>
</asp:SqlDataSource>

我认为在

cbconventioniato

中选择一个项目后，我应该以这种方式过滤

ddlVeicoli

项目。。。但它不起作用。。。为什么?

如果我在调试中查看

sdsVeicoli

SelectParameters

，我可以看到

id\u convenzionato

被正确地设置为所选值（id来自

cbConvenzionato

），我还打赌

sdsNoleggi

数据集将被正确地更新为新值，因为我以前多次这样做过。那为什么不是呢？我还试图在

sdsVeicoli.Select（）

调用之后强制执行

ddlVeicoli.DataBind（）

。。。但这没有效果。

我这样做：

protected void cbConvenzionato_SelectedIndexChanged(object sender, EventArgs e)
{
    ddlVeicoli.DataSource = null;

    sdsVeicoli.Select(DataSourceSelectArguments.Empty);

    ddlVeicoli.DataSource = sdsVeicoli;
    ddlVeicoli.DataBind();

    Search();
}

protected void cbConvenzionato_SelectedIndexChanged(object sender, EventArgs e)
{
    ddlVeicoli.DataSource = null;

    sdsVeicoli.Select(DataSourceSelectArguments.Empty);

    ddlVeicoli.DataSource = sdsVeicoli;
    ddlVeicoli.DataBind();

    Search();
}