急！！关于SqlDataSource

我在页面手动绑定了SqlDataSource 现在我想要在InsertCommand里在加一个字段不过这字段我是在后台获取的我要怎么样把这个字段添加到InsertCommand里的附代码谢谢！！！

 <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:GeDaiSystem %>"

            SelectCommand="SELECT a.ID, a.Name, a.Agent, a.DelegationAmount, a.NewBalance, a.DelegationUnit, 
      a.CaseStatus, a.CaseType, a.AdjustmentCity
FROM GeDai a INNER JOIN
      Legal_services b ON a.P_ID = b.ID"

            UpdateCommand="UPDATE GeDai SET Name = @Name, Agent = @Agent, DelegationAmount = @DelegationAmount, NewBalance = @NewBalance, DelegationUnit = @DelegationUnit, CaseStatus = @CaseStatus, CaseType = @CaseType, AdjustmentCity = @AdjustmentCity WHERE (ID=@ID)"

            InsertCommand="insert into GeDai(legalstatus,Name,Address,TEl,Note,FinalTime,Agent,ArchiveTime,ArchiveManage,ArchiveNo,DelegationAmount,NewBalance,DelegationUnit,CaseStatus,CaseType,AdjustmentCity)values(@legalstatus,@Name,@Address,@TEl,@Note,@FinalTime,@Agent,@ArchiveTime,@ArchiveManage,@ArchiveNo,@DelegationAmount,@NewBalance,@DelegationUnit,@CaseStatus,@CaseType,@AdjustmentCity)"

            DeleteCommand="DELETE FROM GeDai WHERE (ID=@ID)">

            <InsertParameters>

                <asp:Parameter Name="legalstatus" />

                <asp:Parameter Name="Name" />

                <asp:Parameter Name="Address" />

                <asp:Parameter Name="TEl" />

                <asp:Parameter Name="Note" />

                <asp:Parameter Name="FinalTime" />

                <asp:Parameter Name="Agent" />

                <asp:Parameter Name="ArchiveTime" />

                <asp:Parameter Name="ArchiveManage" />

                <asp:Parameter Name="ArchiveNo" />

                <asp:Parameter Name="DelegationAmount" />

                <asp:Parameter Name="NewBalance" />

                <asp:Parameter Name="DelegationUnit" />

                <asp:Parameter Name="CaseStatus" />

                <asp:Parameter Name="CaseType" />

                <asp:Parameter Name="AdjustmentCity" />

                <asp:Parameter Name="TextBox1" />

            </InsertParameters>

            <UpdateParameters>

                <asp:Parameter Name="Name" />

                <asp:Parameter Name="Agent" />

                <asp:Parameter Name="DelegationAmount" />

                <asp:Parameter Name="NewBalance" />

                <asp:Parameter Name="DelegationUnit" />

                <asp:Parameter Name="CaseStatus" />

                <asp:Parameter Name="CaseType" />

                <asp:Parameter Name="AdjustmentCity" />

                <asp:Parameter Name="id" />

            </UpdateParameters>

            <DeleteParameters>

                <asp:Parameter Name="id" />

            </DeleteParameters>

        </asp:SqlDataSource>

--------------------编程问答-------------------- 后台修改这个 SqlDataSource --------------------编程问答--------------------

引用 1 楼 happyer_longlong 的回复:

后台修改这个 SqlDataSource

怎么加的？给个代码吧

行 38:             P_ID = Convert.ToInt32(dropDownList.SelectedValue.ToString());
行 39:             SqlDataSource1.InsertCommand.Insert(P_ID, "@P_ID");
行 40:             SqlDataSource1.InsertParameters["@P_ID"].DefaultValue = P_ID.ToString();
行 41:             DetailsView1.DataSourceID = "SqlDataSource1";
行 42:             DetailsView1.DataBind();

40行报错未将对象引用设置到对象的实例。

补充：.NET技术 ,  C#