Problem with an datagrid solution

Problem with an datagrid solution

Hi All,

I have written an form with several dropdownlists.

I want to show only the things (in an datagrid) of which the user has selected a Item in one of the available dropdownlists. I have written a query of which I think should do the trick, but instead I see nothing :(

Maybe I have forgotten something, but I can't see what. Perhaps some of you may have a idea? Thanks in advance:

The SQL query of the datagrid:

SELECT BandenMerk, Bandenwinter, BandenBreedte, BandenSerie, BandenInch, BandenSpeed, BandenLoad, BandenProfiel, BandenBestelcode, BandenBrutoST, BandenMarge, BandenNettoST FROM Bandenexport WHERE (@bandenmerk IS NULL OR bandenMerk = @bandenmerk) and (@bandenwinter = Null OR bandenwinter = @bandenwinter) and (@BandenBreedte = Null or BandenBreedte = @BandenBreedte) and (@BandenSerie is Null or BandenSerie = @BandenSerie) and (@BandenInch is Null or BandenInch = @BandenInch) and (@BandenSpeed is Null or BandenSpeed = @BandenSpeed) and (@BandenLoad is Null or BandenLoad = @BandenLoad) and (@BandenProfiel is null or BandenProfiel = @BandenProfiel)

The parameterselection :

>
<asp:ControlParameter ControlID="lstMerk" Name="bandenmerk" PropertyName="SelectedValue" DefaultValue="Null" />
<asp:ControlParameter ControlID="lstwinter" Name="bandenwinter" PropertyName="SelectedValue" DefaultValue="" />
<asp:ControlParameter ControlID="lstbreedte" Name="BandenBreedte" PropertyName="SelectedValue" DefaultValue="" />
<asp:ControlParameter ControlID="lstinch" Name="BandenSerie" PropertyName="SelectedValue" />
<asp:ControlParameter ControlID="lstinch" Name="BandenInch" PropertyName="SelectedValue" />
<asp:ControlParameter ControlID="lstspeed" Name="BandenSpeed" PropertyName="SelectedValue" />
<asp:ControlParameter ControlID="lstLoad" Name="BandenLoad" PropertyName="SelectedValue" />
<asp:ControlParameter ControlID="lstProfiel" Name="BandenProfiel" PropertyName="SelectedValue" />
SelectParameters>

properties of the gridview:

<

asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="BandenView">

If nothing is selected by the user, all records should bee shown.

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