Sql 错误[42000]不允许使用名称WHSER

我的ControlParameter标记的变量@Whser出现名称错误

是什么原因造成的

<asp:SqlDataSource ID="SqlDataSource1" runat="server"
    ConnectionString="<%$ ConnectionStrings:AS400fr %>" 
    ProviderName="<%$ ConnectionStrings:AS400fr.ProviderName %>" 

    SelectCommand="SELECT PO180M1.POORNO AS PO_No, PO180M1.POSTAT AS PO_Status, PO180M2.PHSTAT AS LineStatus, PO180M1.POVNNO AS Vendor_No, PO180M1.POVNNM AS Vendor, PO180M1.POWHSE AS Whse, PO180M2.PHLNNO AS LineNo, PO180M2.PHPPN AS PartNo, PO180M2.PHVNPD AS PartDesc1, PO180M2.PHVNP2 AS PartDesc2, PO180M2.PHORTP, PO180M2.PHTYPE, PO180M1.POORDT AS OrderDate, PO180M2.PHLNEX AS DueDate, PO180M1.POCLDT, PO180M2.PHPUOQ AS OrderQty, PO180M2.PHPURQ AS RecdQty, PO180M2.PHUNCT AS UnitCost, PO180M2.PHSKUM AS StockingUOM, PO180M2.PHPUUM AS PurchgUOM, PO180M2.PHPUOQ - PO180M2.PHPURQ AS QtyRemng FROM PO180M1, PO180M2 WHERE PO180M1.POORNO = PO180M2.PHORNO AND (PO180M2.PHPUOQ - PO180M2.PHPURQ &gt; 0) AND (PO180M1.POSTAT = 'O') AND (PO180M1.POWHSE = @Whser) ORDER BY Vendor_No DESC, OrderDate">

  <SelectParameters>
    <asp:ControlParameter Name="Whser" ControlID="DropDown1" DbType="Object" PropertyName="SelectedValue" Type="String"/>
  </SelectParameters>
</asp:SqlDataSource>