Question

I have encountered this error: Must declare the scalar variable “@UserId” when i am trying to delete one particular row in my SqlServer. I had already declare the UserId in the DeleteParameters, but this error still appear.

Exception Details: System.Data.SqlClient.SqlException: Must declare the scalar variable > "@UserId".

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Here is my code:

<asp:SqlDataSource ID="SqlDataSource1" runat="server" 
    ConnectionString="<%$ ConnectionStrings:ASPNETDBConnectionString1 %>" 
    SelectCommand="SELECT aspnet_Membership.Email, Details.CustName, Details.CustNum, Details.CustRole, Details.CustStatus, Details.PName, Details.PEmail, Details.PRole, Details.WedDate, aspnet_Users.UserName, Details.UserId FROM Details INNER JOIN aspnet_Membership ON Details.UserId = aspnet_Membership.UserId INNER JOIN aspnet_Users ON aspnet_Membership.UserId = aspnet_Users.UserId WHERE (Details.UserId = @UserId)"
    UpdateCommand="update Details SET CustName = @CustName, CustNum = @CustNum, CustRole = @CustRole, CustStatus = @CustStatus, PName = @PName, PEmail = @PEmail, PRole = @PRole, WedDate = @WedDate WHERE [UserId] = @UserId Update aspnet_Membership Set Email= @email WHERE [UserId] = @UserId"
    DeleteCommand="DELETE FROM Details WHERE [UserId] = @UserId">
    <DeleteParameters>
        <asp:Parameter Name="UserId" type="String" />
        <asp:Parameter Name="CustName" />
        <asp:Parameter Name="CustNum" />
        <asp:Parameter Name="CustRole" />
        <asp:Parameter Name="CustStatus" />
        <asp:Parameter Name="PName" />
        <asp:Parameter Name="PEmail" />
        <asp:Parameter Name="PRole" />
        <asp:Parameter Name="WedDate" />
        <asp:Parameter Name="email" />
    </DeleteParameters>
    <SelectParameters>
        <asp:ControlParameter ControlID="lblHidden" Name="UserId"
        PropertyName="Text" />
    </SelectParameters>
    <UpdateParameters>
        <asp:Parameter Name="CustName" />
        <asp:Parameter Name="CustNum" />
        <asp:Parameter Name="CustRole" />
        <asp:Parameter Name="CustStatus" />
        <asp:Parameter Name="PName" />
        <asp:Parameter Name="PEmail" />
        <asp:Parameter Name="PRole" />
        <asp:Parameter Name="WedDate" />
        <asp:Parameter Name="UserId" />
        <asp:Parameter Name="email" />
    </UpdateParameters>
</asp:SqlDataSource>
<asp:DetailsView ID="DetailsView1" runat="server"
    AutoGenerateRows="False" DataSourceID="SqlDataSource1"
    Height="50px" Width="125px">
    <Fields>
        <asp:BoundField DataField="Email" HeaderText="Email"
            SortExpression="Email" />
        <asp:BoundField DataField="CustName" HeaderText="CustName"
            SortExpression="CustName" />
        <asp:BoundField DataField="CustNum" HeaderText="CustNum"
            SortExpression="CustNum" />
        <asp:BoundField DataField="CustRole" HeaderText="CustRole"
            SortExpression="CustRole" />
        <asp:BoundField DataField="CustStatus" HeaderText="CustStatus"
            SortExpression="CustStatus" />
        <asp:BoundField DataField="PName" HeaderText="PName"
            SortExpression="PName" />
        <asp:BoundField DataField="PEmail" HeaderText="PEmail"
            SortExpression="PEmail" />
        <asp:BoundField DataField="PRole" HeaderText="PRole"
            SortExpression="PRole" />
        <asp:BoundField DataField="WedDate" HeaderText="WedDate"
            SortExpression="WedDate" />
        <asp:BoundField DataField="UserName" HeaderText="UserName"
            SortExpression="UserName" />
        <asp:BoundField DataField="UserId" HeaderText="UserId"
            SortExpression="UserId" />
        <asp:CommandField ShowDeleteButton="True"
            ShowEditButton="True" />
    </Fields>
</asp:DetailsView>
<asp:Label ID="lblHidden" runat="server" Text="Label" Visible="False">
</asp:Label>

Answer 1

I think you have pasted T-SQL query as it was. I want to explain you what you are doing here:

SELECT aspnet_Membership.Email, Details.CustName, Details.CustNum, 
    Details.CustRole, Details.CustStatus, Details.PName, Details.PEmail, 
    Details.PRole, Details.WedDate, aspnet_Users.UserName, Details.UserId 
FROM Details 
INNER JOIN aspnet_Membership ON Details.UserId = aspnet_Membership.UserId 
INNER JOIN aspnet_Users ON aspnet_Membership.UserId = aspnet_Users.UserId 
WHERE (Details.UserId = @UserId) 

this query retrieves the data from the following table on the basis of UserId

1. Details
2. aspnet_Membership
3. aspnet_Users

You have to pass UserId to the SqlDataSource to perform its function: Read about how to INSERT, UPDATE and DELETE with SQLDataSource