Selecting Where Cloumn = Column OR Column = Value

Hi

I have a gridview with a sql data source and a few drop down lists where i choose values to sorth what i would like to retrive from the table. The problem im facing is that when i pass values to the database, i can sort out and retrive my items when both my listboxes have selected values.

But when i want to select everything from the table where the column = clumn or cloumn = value i dont get anything back.

I have 2 dropdown lists. One for category and one for location. These are populated drom the database by selecting the column and retriving destinct values. I have a function that fires when one of the dropdown lists are changed witch changes the sql datasource select value so it retrives items sorted by the selected categories and locations.

Here is the function:

    protected void DropDownList_Change(object sender, EventArgs e)
    {
        string Category = DropDownListKategori.SelectedValue.ToString();
        string Location = DropDownListEtabl.SelectedValue.ToString();
        SqlDataSource1.SelectCommand = "SELECT ARTNR, ARTTYP, AKTIVITET, DATUM, KUND, PLATS, KOMMENTAR FROM ARTIKEL WHERE ARTTYP = @ARTTYP AND PLATS = @PLATS";
        SqlDataSource1.SelectParameters.Clear();
        SqlDataSource1.SelectParameters.Add(@"ARTTYP", Category);
        SqlDataSource1.SelectParameters.Add(@"PLATS", Location);
        SqlDataSource1.DataBind();

    }

The dropdown lists have an option to not retrive values by category or location. I have set that value to PLATS and ARTTYP thinking the query would would retrive everything if these were selected

SELECT ARTNR, ARTTYP, AKTIVITET, DATUM, KUND, PLATS, KOMMENTAR FROM ARTIKEL WHERE ARTTYP = ARTTYP AND PLATS = PLATS

however if both these drop down lists are set to not filter, my query gets nothing in return. And if one of the lists has this selected and ther other one has a value, say a location or something nothing is retrived either. However if both columns have something selected i do get values returned.

My speculation is that the query beeing run when this happens is that it is trying to find columns having the value ARTTYP or PLATS (category or location), as a string and actually seeing it as Im trying to retrive values where column = column.

Any suggestions on how i can make my query run as intended or is there another problem Im not seeing.