DropDownListboxes - 为什么要添加这些数据？

Question

I have three dropdownlistboxes that are populated with "select distinct" queries and it works fine at first glance. Ddl1 has only one of each item from the database, and then ddl2 has only one of each item that go with what was selected in ddl1, until you change ddl1, then it adds what was in ddl2 from the first selection to the 2nd selection.

just to give further explanation of what is happening:

if the first one has A, B, C and you select A, the second one with show D, E, and F. then if you decide to go back and change the first one to B the second has G, H, I, AND it still has D, E, F, when it should only have G, H, and I

What am I doing wrong?

Here are my datasources:

        <asp:SqlDataSource ID="LEDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:AXMAPConnectionString %>" SelectCommand="SELECT DISTINCT [LegalEntity] FROM [AXMAP].[Customers]"></asp:SqlDataSource>
    <asp:SqlDataSource ID="OSEDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:AXMAPConnectionString %>" SelectCommand="SELECT DISTINCT [OldSourceEnvironment] FROM [AXMAP].[Customers] WHERE LegalEntity = @LegalEntity">
        <SelectParameters>
            <asp:ControlParameter ControlID="ddlLegalEntity" PropertyName="SelectedValue" Type="String" Name="LegalEntity" DefaultValue="-- Please Select --" />
        </SelectParameters>
    </asp:SqlDataSource>
                <asp:SqlDataSource ID="OCCDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:AXMAPConnectionString %>" SelectCommand="SELECT DISTINCT [OldCompanyCode] FROM [AXMAP].[Customers] WHERE LegalEntity = @LegalEntity AND OldSourceEnvironment = @OldSourceEnvironment">
                    <SelectParameters>
                        <asp:ControlParameter ControlID="ddlLegalEntity" PropertyName="SelectedValue" Type="String" Name="LegalEntity" DefaultValue="-- Please Select --" />
                        <asp:ControlParameter ControlID="ddlOldSourceEnvironment" PropertyName="SelectedValue" Type="String" Name="OldSourceEnvironment" DefaultValue="-- Please Select --" />
                    </SelectParameters>
    </asp:SqlDataSource>

And Here are my dropdownlists:

                <td class="auto-style6">
                <asp:DropDownList ID="ddlLegalEntity" runat="server" AutoPostBack="True" DataSourceID="LEDataSource" DataTextField="LegalEntity" DataValueField="LegalEntity" Width="135px" AppendDataBoundItems="True">
                <asp:ListItem Selected="True" Value="0" Text="-- Please Select --"></asp:ListItem>
                </asp:DropDownList>
            </td>
        </tr>
        <tr>
            <td class="auto-style6">
                <asp:DropDownList ID="ddlOldSourceEnvironment" runat="server" AutoPostBack="true" DataSourceID="OSEDataSource" DataTextField="OldSourceEnvironment" DataValueField="OldSourceEnvironment" AppendDataBoundItems="true" Width="135px">
                <asp:ListItem Selected="True" Value="0" Text="-- Please Select --"></asp:ListItem>                    
                </asp:DropDownList>
            </td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td class="auto-style6">
                <asp:DropDownList ID="ddlOldCompanyCode" runat="server" AutoPostBack="true" DataSourceID="OCCDataSource" DataTextField="OldCompanyCode" DataValueField="OldCompanyCode" AppendDataBoundItems="true" Width="135px">
                <asp:ListItem Selected="True" Value="0" Text="-- Please Select --"></asp:ListItem>  
                </asp:DropDownList>

Answer 1

你已经设定好了

 AppendDataBoundItems="true"