Joins On Uniqueidentifier Columns

I have recently introduced Microsoft’s
user/roles facility by running aspnet_regsql.exe against my database so that I
would be able to link activities with staff members.



In testing I was able to

Join 2
tables (Reservations and aspnet_Users) with the join fields being of type
uniqueidentifier, using SQL Server Manager Studio Express diagram
facility; Create
a record in aspnet_Users using Microsoft’s
Website Admin toolCreate
a record in Reservations and paste in the contents of uniqueidentifier
field in aspnet_Users using SQL Server Manager Studio Express




All the basic tests had been fine so I created a web page
with a detailsview of the Reservations table and made a templated field (in the
insertitemtemplate), replaced the text box with a dropdown and did a bind of
that dropdown to the relevant records in the aspnet_Users table i.e. UserName
and UserId columns with UserName being displayed. The source is as follows:


    <asp:TemplateField HeaderText="Taken By" SortExpression="RES_Taken_By_Staff_ID">


                    <EditItemTemplate>


                        <asp:TextBox ID="TextBox5" runat="server" Text='<%#
Bind("RES_Taken_By_Staff_ID") %>'></asp:TextBox>


                    </EditItemTemplate>


                    <InsertItemTemplate>


                        <asp:DropDownList ID="DropDownList5" runat="server" DataSourceID="SDSStaff" DataTextField="UserName"


                            DataValueField="UserId">


                        </asp:DropDownList><br />


                        <asp:SqlDataSource ID="SDSStaff" runat="server" ConnectionString="<%$ ConnectionStrings:ReservationsDBConnectionString %>"


                            SelectCommand="SELECT
[UserId], [UserName] FROM [vw_aspnet_Users]"></asp:SqlDataSource>


                    </InsertItemTemplate>


                    <ItemTemplate>


                        <asp:Label ID="Label5" runat="server" Text='<%#
Bind("RES_Taken_By_Staff_ID") %>'></asp:Label>


                    </ItemTemplate>


                </asp:TemplateField>


           

 

Everything looks OK, the correct data appears in the dropdown
but when I hit the INSERT button I receive the following failure message:

 

Implicit conversion from data type sql_variant to uniqueidentifier is
not allowed. Use the CONVERT function to run this query.

Description: An unhandled exception
occurred during the execution of the current web request. Please review the
stack trace for more information about the error and where it originated in the
code.



Exception Details: System.Data.SqlClient.SqlException: Implicit
conversion from data type sql_variant to uniqueidentifier is not allowed. Use
the CONVERT function to run this query.

 

 

I can’t quite see what I should do so I would be
grateful for any help.