VS2005 中选择gridview1的某行，gridview2显示其他信息的问题！
如题，2个gridview都是自定义的数据源，现在的问题是取第一个gridview的行号时老是有问题，代码：

VB.NET code

    Protected Sub GridView1_SelectedIndexChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSelectEventArgs) Handles GridView1.SelectedIndexChanging        Dim comm As Data.SqlClient.SqlCommand        Dim da As Data.SqlClient.SqlDataAdapter        Dim dt, su As Data.DataTable        Dim xsdd As String ‘第一个gridview的行号变量        xsdd = Me.GridView1.SelectedRow.Cells(3).Text()        '这里报错，“[color=#FF0000]未将对象引用设置到对象的实例[/color]”        comm = New Data.SqlClient.SqlCommand("SELECT sp_xsdh,sp_mx,sp_sl,sp_dj,sp_je,sp_bz,hkrq,fpje,kprq,kpdw,fph FROM spmx WHERE sp_xsdh = '" & xsdd & "'", conn)        da = New Data.SqlClient.SqlDataAdapter        su = CType(GridView2.DataSource, Data.DataTable)        'su.AcceptChanges()        comm.CommandType = Data.CommandType.Text        da.SelectCommand = comm        dt = New Data.DataTable        da.Fill(dt)        GridView2.DataSource = dt        'Dim r As Data.DataRow = su.NewRow        'r.Item(0) = "合计："        'r.Item("sp_je") = su.Compute("sum(sp_je)", "")        'su.Rows.Add(r)        GridView2.DataBind()    End Sub