delete from gridview using stored procedure

Question

Hi i have a gridview, linked to a sqldatasource. I have added a stored procedure to delete from multiple tables, and then enabled deleting on the gridviews smart tag.

When i click the delete button i get an error message, "Object must implement IConvertible". I read that it is a problem passing the parameter to the stored procedure, possibly the wrong datatype being passed. Im not sure if i am passing the parameter to the stored procedure at all. The parameter should be the gridviews datakeyname, in this case it is "UserId".

The stored procedure works i fine in management studio, so i think it is just the parameter being passed (or possibly not being passed)

Do i have to code the parameter in the code behind to be passed to the stored procedure?

<asp:SqlDataSource ID="selectUsers" runat="server" ConnectionString="<%$ ConnectionStrings:CASSFConnectionString %>"
        SelectCommand="SELECT aspnet_Membership.UserId, aspnet_Membership.IsLockedOut, aspnet_Membership.Email, aspnet_Membership.CreateDate, aspnet_Membership.LastLoginDate, aspnet_Membership.LastPasswordChangedDate, aspnet_Profile.PropertyValuesString, aspnet_Users.UserName, aspnet_Membership.IsApproved FROM aspnet_Membership INNER JOIN aspnet_Profile ON aspnet_Membership.UserId = aspnet_Profile.UserId INNER JOIN aspnet_Users ON aspnet_Membership.UserId = aspnet_Users.UserId AND aspnet_Profile.UserId = aspnet_Users.UserId WHERE (CONVERT (nvarchar(256), aspnet_Profile.PropertyValuesString) = @district)" 
        DeleteCommand="DeleteUsers" DeleteCommandType="StoredProcedure" UpdateCommand="UPDATE [aspnet_Membership] SET [IsApproved] = @IsApproved, [Email] = @email, [IsLockedOut] = @IsLockedOut WHERE [aspnet_Membership].[UserId] = @UserID">
        <SelectParameters>
            <asp:ControlParameter ControlID="DropDownList1" Name="district" PropertyName="SelectedValue" />
        </SelectParameters>
        <DeleteParameters>
            <asp:Parameter Name="UserId" Type="String" />
        </DeleteParameters>
        <UpdateParameters>
            <asp:Parameter Name="IsApproved" />
            <asp:Parameter Name="email" />
            <asp:Parameter Name="IsLockedOut" />
            <asp:Parameter Name="UserID" />
        </UpdateParameters>
    </asp:SqlDataSource>

Answer 1

Found the answer, i had just to remove Type="String" from the delete parameter.