Linq to SQL Where ControlParameter for text in dropdownlist

Hi EE,

I have an asp page with 4 dropdownlists (DD) and a grid.  When a user selects a dropdown(DD)  it automatically fills the next  DD according to the selectedvalue.
Everything works fine when using the selected value, but on my last DD I have to take the text from the 3rd DD to filter the last DD.
For example, the 3rd DD has a list with CityID and  CityName, instead of filtering the last DD by CityID, I need to match the CityName field with the SalonCity field in the last DD.
How would I do this using Linq to SQL?
Thanks

<td>    
                         <asp:DropDownList ID="ddCity" Width="95%"  runat="server" AutoPostBack="True" 
                              DataSourceID="DSCities" DataTextField="CityName" 
                              DataValueField="CityLUID">
                         </asp:DropDownList>                                
                         <asp:LinqDataSource ID="DSCities" runat="server" 
                              ContextTypeName="SalonClassesDataContext" OrderBy="CityName" 
                              Select="new (CityLUID, CityName)" TableName="CitysLUs" 
                              Where="StateID == @StateID">
                              <WhereParameters>
                                   <asp:ControlParameter ControlID="ddState" Name="StateID" 
                                        PropertyName="SelectedValue" Type="Int32" />
                              </WhereParameters>
                         </asp:LinqDataSource>
                    </td>
                    <td>
                         <asp:DropDownList ID="ddSalonName"  Width="95%" runat="server" 
                              AutoPostBack="True" DataSourceID="DSSalonNames" DataTextField="SalonName" 
                              DataValueField="StylistID">
                         </asp:DropDownList>                                
                         <asp:LinqDataSource ID="DSSalonNames" runat="server" 
                              ContextTypeName="SalonClassesDataContext" OrderBy="SalonName" 
                              Select="new (StylistID, SalonName)" TableName="Stylists" 
                              Where="SalonCity == @CityName">
                              
                              <WhereParameters>
                                   <asp:ControlParameter ControlID="ddCity" Name="CityName" 
                                        PropertyName="SelectedItem" Type="String" />
                              </WhereParameters>
                         </asp:LinqDataSource>
                    </td>

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