多行Gridview更新

Question

我正在尝试使用gridview更新/插入多行。一切都正确显示，直到我按下订单按钮。这是我的错误：

 "Object reference not set to an instance of an object"

问题似乎在这里，但我不确定： FloorstockOrder.IsRowModified（GridViewRow row）

这是我的代码：         System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent（String eventArgument）+10         System.Web.UI.Page.RaisePostBackEvent（IPostBackEventHandler sourceControl，String eventArgument）+13         System.Web.UI.Page.RaisePostBackEvent（NameValueCollection postData）+36         System.Web.UI.Page.ProcessRequestMain（Boolean includeStagesBeforeAsyncPoint，Boolean includeStagesAfterAsyncPoint）+1565

    System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
    System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
    System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
    System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565



<asp:SqlDataSource ID="SqlDataSource4" runat="server" 
            ConnectionString="<%$ ConnectionStrings:rx_empConnectionString_PICUSER %>" SelectCommand="select ABS(CHECKSUM(NewID())) as ID, drug Drug, null Qty
from
floorstock_meds
where
area = @area" UpdateCommand="insert into floorstock_order
(drug, area, qty, order_date)
values (@drug, @area, @qty, getdate())">
            <SelectParameters>
                <asp:ControlParameter ControlID="DropDownList1" Name="area" 
                    PropertyName="SelectedValue" />
            </SelectParameters>
            <UpdateParameters>
                <asp:ControlParameter ControlID="GridView2" Name="drug" 
                    PropertyName="SelectedValue" />
                    <asp:ControlParameter ControlID="DropDownList1" Name="area" 
                    PropertyName="SelectedValue" />
                <asp:ControlParameter ControlID="GridView5" Name="Qty" 
                    PropertyName="SelectedValue" />

            </UpdateParameters>
        </asp:SqlDataSource>
        </div>

   <div>
   <asp:GridView ID="GridView5" runat="server" 
                             AllowPaging="True" 
                             DataSourceID="SqlDataSource4" 
                             AutoGenerateColumns="False" DataKeyNames="ID">
<Columns>
    <asp:TemplateField HeaderText="Select">
    <ItemTemplate>
    <asp:CheckBox ID="chkSelect" runat="server" 
                  AutoPostBack="true" 
             OnCheckedChanged="chkSelect_CheckedChanged"/>
    </ItemTemplate>

    </asp:TemplateField>
    <asp:BoundField DataField="ID" HeaderText="ID" 
                                   SortExpression="ID"/>

    <asp:BoundField DataField="Drug" HeaderText="Drug" 
                                   SortExpression="Drug"/>

    <asp:TemplateField HeaderText="Qty" 
                       SortExpression="Qty">
    <ItemTemplate>
    <asp:TextBox ID="txtName" runat="server" 
                 Text='<%# Bind("Qty") %>' ReadOnly="true" 
                 ForeColor="Blue" BorderStyle="none" 
                 BorderWidth="0px" >
    </asp:TextBox>
    </ItemTemplate>
    </asp:TemplateField>

    </Columns>
</asp:GridView>

<asp:Button ID="Button2" runat="server" 
            OnClick="btnUpdate_Click" Text="Order" /><br />


Private strConnection As String = ConfigurationManager.ConnectionStrings("ConnectionString").ConnectionString
    Private tableCopied As Boolean = False
    Private originalTable As DataTable

    Protected Sub GridView5_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
        If e.Row.RowType = DataControlRowType.DataRow Then
            If Not tableCopied Then
                originalTable = DirectCast(e.Row.DataItem, System.Data.DataRowView).Row.Table.Copy()
                ViewState("originalValues") = originalTable
                tableCopied = True
            End If
        End If
    End Sub
    Protected Sub btnUpdate_Click(ByVal sender As Object, ByVal e As EventArgs)
        originalTable = DirectCast(ViewState("originalValues"), DataTable)
        For Each row As GridViewRow In GridView5.Rows
            If IsRowModified(row) Then
                GridView5.UpdateRow(row.RowIndex, False)
            End If
        Next
        tableCopied = False
        GridView5.DataBind()
    End Sub
    Protected Function IsRowModified(ByVal row As GridViewRow) As Boolean
        Dim ID As Integer
        Dim qty As String
        Dim area As String

        ID = Convert.ToInt32(GridView5.DataKeys(row.RowIndex).Value)

        qty = DirectCast(row.FindControl("txtName"), TextBox).Text
        area = DirectCast(row.FindControl("DropDownList1"), DropDownList).SelectedValue

        Dim newRow As System.Data.DataRow = originalTable.[Select]([String].Format("ID = {0}", ID))(0)

        If Not qty.Equals(newRow("qty").ToString()) Then
            Return True
        End If
        If Not area.Equals(newRow("area").ToString()) Then
            Return True
        End If

        Return False


    End Function
    Protected Sub chkSelect_CheckedChanged(ByVal sender As Object, ByVal e As EventArgs)
        Dim chkTest As CheckBox = DirectCast(sender, CheckBox)
        Dim grdRow As GridViewRow = DirectCast(chkTest.NamingContainer, GridViewRow)
        Dim txtname As TextBox = DirectCast(grdRow.FindControl("txtName"), TextBox)

        If chkTest.Checked Then
            txtname.[ReadOnly] = False
            txtname.ForeColor = System.Drawing.Color.Black
        Else
            txtname.[ReadOnly] = True
            txtname.ForeColor = System.Drawing.Color.Blue

        End If
    End Sub