如何使用SqlDataSource选择级联的DropDownList

Question

我的数据库中有以下内容-

breedId Species Breed
0       dog      Alsatian
1       dog      pitbull
2       dog      Shetland sheepdog
3       dog      Boxer
4       cat      Dragon Li
5       cat      Australian Mist
6       cat      Korat

在c＃设计器视图中，我有2个下拉列表，其中一个包含品种，另一个包含品种。

我想要的是，当用户在物种列表中选择“狗”时，品种列表应具有以下Alsatian, pitbull, Shetland sheepdog,Boxer犬，比特犬Alsatian, pitbull, Shetland sheepdog,Boxer

当我选择“狗”时，将显示数据库中的所有品种。

<asp:DropDownList ID="DropDownListSpecies" runat="server" 
     Height="27px" Width="107px" DataSourceID="hs330" 
     DataTextField="Species" DataValueField="Species">
</asp:DropDownList>
<asp:SqlDataSource ID="Species" runat="server" 
     ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
     SelectCommand="SELECT DISTINCT [Species] FROM [Breed]">
</asp:SqlDataSource>

<asp:DropDownList ID="DropDownListBreed" runat="server" Height="20px" 
    Width="110px" DataSourceID="breed" DataTextField="Breed" 
    DataValueField="Breed">
</asp:DropDownList>
<asp:SqlDataSource ID="breed" runat="server" 
    ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
    SelectCommand="SELECT DISTINCT [Breed] FROM [Breed]">
</asp:SqlDataSource>

Answer 1

您需要在SelectParameters中使用ControlParameter 。

确保DropDownListSpecies的 AutoPostBack =“ True”

仅供参考：您在Speecies中有错字

<asp:DropDownList ID="DropDownListSpecies" runat="server"
    Height="27px" Width="107px" DataSourceID="Species"
    DataTextField="Species" DataValueField="Species" AutoPostBack="True">
</asp:DropDownList>
<asp:SqlDataSource ID="Species" runat="server"
    ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
    SelectCommand="SELECT DISTINCT [Species] FROM [Breed]"></asp:SqlDataSource>
<asp:DropDownList ID="DropDownListBreed" runat="server"
    Height="20px" Width="110px"
    DataSourceID="breed" DataTextField="Breed" DataValueField="Breed">
</asp:DropDownList>
<asp:SqlDataSource ID="breed" runat="server"
    ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
    SelectCommand="SELECT DISTINCT [Breed] FROM [Breed] WHERE Species=@Species">
    <SelectParameters>
        <asp:ControlParameter ControlID="DropDownListSpecies" PropertyName="SelectedValue"
            Name="Species " Type="String" DefaultValue="cat" />
    </SelectParameters>
</asp:SqlDataSource>

Answer 2

您不会根据第一个下拉列表中的选择（这就是您想要的）来过滤第二个下拉列表中的数据。

    <asp:DropDownList ID="DropDownListBreed" runat="server" Height="20px" Width="110px" DataSourceID="breed" DataTextField="Breed" DataValueField="Breed">
    </asp:DropDownList>
    <asp:SqlDataSource ID="breed" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>" SelectCommand="SELECT DISTINCT [Breed] FROM [Breed] WHERE Species = @Species">
    <SelectParameters>
        <asp:ControlParameter ControlID="DropDownListSpecies" PropertyName="SelectedValue"
            Name="Species " Type="String" DefaultValue="cat" />
    </SelectParameters>
</asp:SqlDataSource>

另外，如果希望在更改每个DropDownList的值后立即反映出更改，则需要向每个DropDownList添加AutoPostBack =“ True”属性。