First foray into .NET so please be gentle............

Please note: there are extra spaces in the code near the < > tags. UT could not accept the original formatting

Following an example in an online tutorial I have the following code

    < asp:SqlDataSource ID="myFilteringDataSource" runat="server"
        ConnectionString="< %$ ConnectionStrings:RLP_SPOTLIGHTConnectionString % >" 
        ProviderName="< %$ ConnectionStrings:RLP_SPOTLIGHTConnectionString.ProviderName % >" 
        SelectCommand="SELECT DISTINCT buyer_type FROM open_order"
    / >
    < asp:DropDownList ID="myDropDownList" runat="server"
        DataSourceID   = "myFilteringDataSource"
        DataValueField = "buyer_type"
        AutoPostBack   = "True"
     / >

    <br />
    <br />
    < asp:SqlDataSource ID="MySqlOpen_Order" runat="server" 
        ConnectionString="< %$ ConnectionStrings:RLP_SPOTLIGHTConnectionString % >" 
        ProviderName="< %$ ConnectionStrings:RLP_SPOTLIGHTConnectionString.ProviderName % >" 
        SelectCommand="SELECT * FROM open_order">      
    < /asp:SqlDataSource >


    < asp:GridView ID="GridView1" runat="server" DataSourceID="MySqlOpen_Order" 
                             etc

This code works in that both the dropdown list and the grid display properly.

Again based on sample code from the tutorial I've tried to modify the code to have the grid based upon the value of the dropdown
with the modified code as follows

< asp:SqlDataSource ID="MySqlOpen_Order" runat="server" 
     ConnectionString="< %$ ConnectionStrings:RLP_SPOTLIGHTConnectionString % >" 
     ProviderName="< %$ ConnectionStrings:RLP_SPOTLIGHTConnectionString.ProviderName % >" 
     SelectCommand="SELECT * FROM open_order where buyer_type = @buyer_type">      
        
     < SelectParameters>
      < asp:ControlParameter Name="buyer_type" ControlID="myDropDownList" PropertyName="SelectedValue" / >
    < /SelectParameters>
< /asp:SqlDataSource>

When this version of the code runs the dropdown list appears but the grid never gets populated. Selecting a new value from the dropdown doesn't do anything.

All suggestions gratefully appreciated

.........Rich