问一个有关ObjectDataSource控件的参数问题

大家帮忙看看，删除的时候提示没有参数？<fieldset style="padding:15px;" >
        <legend>ObjectDataSource控件使用Demo</legend>
        <br />
        请选择地区：<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" DataSourceID="ObjectDataSource_State" DataTextField="state" DataValueField="state">
        </asp:DropDownList>
        <asp:ObjectDataSource ID="ObjectDataSource_State" runat="server" SelectMethod="GetStates" TypeName="AuthorDB"></asp:ObjectDataSource>
        <br />
        <asp:GridView ID="GridView1" AutoGenerateColumns="false" runat="server" AllowPaging="True" AllowSorting="True" DataSourceID="ObjectDataSource_GridView" Width="100%" >
            <Columns>
                <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" ShowSelectButton="True" >
                    <ItemStyle Width="13%" />
                </asp:CommandField>
               <asp:BoundField DataField="au_id" HeaderText="au_id" SortExpression="au_id" />
               <asp:BoundField DataField="au_fname" HeaderText="au_fname" SortExpression="au_fname"/>
               <asp:BoundField DataField="au_lname" HeaderText="au_lname" SortExpression="au_lname"/>
               <asp:BoundField DataField="state" HeaderText="state" SortExpression="state"/>
            </Columns>
            <SelectedRowStyle BackColor="ControlDark" />
        </asp:GridView>
        
        <asp:ObjectDataSource ID="ObjectDataSource_GridView" runat="server" TypeName="AuthorDB" UpdateMethod="UpdateAuthor" DeleteMethod="DeleteAuthors" InsertMethod="InsertAuthor" SelectMethod="GetAuthorsByState" >
           
            <UpdateParameters>
                <asp:Parameter Name="au_id" Type="String" />
                <asp:Parameter Name="au_lname" Type="String" />
                <asp:Parameter Name="au_fname" Type="String" />
                <asp:Parameter Name="state" Type="String" />
            </UpdateParameters>
             <DeleteParameters>
                <asp:Parameter Name="au_id"  Type="String" /> 
            </DeleteParameters>
            <SelectParameters>
                <asp:ControlParameter ControlID="DropDownList1" Name="state" PropertyName="SelectedValue"
                    Type="String" />
            </SelectParameters>
            <InsertParameters>
                <asp:Parameter Name="au_lname" Type="String" />
                <asp:Parameter Name="au_fname" Type="String" />
                <asp:Parameter Name="state" Type="String" />
            </InsertParameters>
        </asp:ObjectDataSource>
        <br />
    </fieldset>