ต้องการค้นหาแบบมีเงื่อนไงโดยใช้ DropDownList จะต้องเขียนอย่างไรคะ ตัวอย่างดังรูป..

    Protected Sub btnSubmit_Click(sender As Object, e As System.EventArgs) Handles btnSubmit.Click
        Dim strSQL As String = "select aa.GoodCode," & _
                                       "aa.GoodName1," & _
                                       "bb.GoodCateCode+' '+bb.GoodCateName GoodCate," & _
                                       "cc.GoodGroupCode+' '+cc.GoodGroupName GoodGroup," & _
                                       "dd.GoodPattnCode+' '+dd.GoodPattnName GoodPattn," & _
                                       "ee.GoodBrandName," & _
                                       "ff.Remark(GoodModel)" & _
                               "from  EMGood aa ," & _
                                      "EMGoodCate bb ," & _
                                      "EMGoodGroup cc ," & _
                                      "EMGoodPattn dd ," & _
                                      "EMGoodBrand ee ," & _
                                      "EMGoodRemarkHD ff" & _
                                      "where"

        Select Case ddlGroupBy.SelectedValue

            Case 1
                ' Case 1 ค้นหาด้วยรหัสสินค้า
                strSQL = strSQL & "aa.GoodCode LIKE '%" & txtTag.Text & "%'"

            Case 2
                ' Case 2 ค้นหาด้วยชื่อ
                strSQL = strSQL & "aa.GoodName1 LIKE '%" & txtTag.Text & "%'"

        End Select


        Dim da As New SqlDataAdapter(strSQL, condb)
        da.Fill(ds, "select")
        dt = ds.Tables("select").Rows(0)

        lblName.Text = dt("GoodName1")
        lblProductCode.Text = dt("GoodCode")
        lblGroup.Text = dt("GoodGroupCode")
        lblDesign.Text = dt("GoodPattnCode")
        lblBrand.Text = dt("GoodBrandName")
        lblModel.Text = dt("GoodModel")