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这面这段代码为什么不能绑定GridView1 控件调了一个晚上没能成功
一执行的时候就提示：   在 System.Web.UI.WebControls.BoundField.GetValue(Control controlContainer)
   在 System.Web.UI.WebControls.BoundField.OnDataBindField(Object sender, EventArgs e)
   在 System.Web.UI.Control.OnDataBinding(EventArgs e)
   在 System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding)
   在 System.Web.UI.Control.DataBind()
   在 System.Web.UI.Control.DataBindChildren()
   在 System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding)
   在 System.Web.UI.Control.DataBind()
   在 System.Web.UI.WebControls.GridView.CreateRow(Int32 rowIndex, Int32 dataSourceIndex, DataControlRowType rowType, DataControlRowState rowState, Boolean dataBind, Object dataItem, DataControlField[] fields, TableRowCollection rows, PagedDataSource pagedDataSource)
   在 System.Web.UI.WebControls.GridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding)
   在 SmartLib.asp.net.Controls.GridViewEx.CreateChildControls(IEnumerable dataSource, Boolean dataBinding) 位置 D:\开发\出版社\测试代码\jzlib\Smartlib\asp.net\Controls\GridViewEx.cs:行号 371
   在 System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable data)
   在 System.Web.UI.WebControls.GridView.PerformDataBinding(IEnumerable data)
   在 System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data)
   在 System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback)
   在 System.Web.UI.WebControls.DataBoundControl.PerformSelect()
   在 System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
   在 System.Web.UI.WebControls.GridView.DataBind()
   在 SmartLib.asp.net.Controls.GridViewEx.BindDataTable(DataTable table) 位置 D:\开发\出版社\测试代码\jzlib\Smartlib\asp.net\Controls\GridViewEx.cs:行号 472
   在 SmartLib.asp.net.Controls.GridViewEx.OnBind() 位置 D:\开发\出版社\测试代码\jzlib\Smartlib\asp.net\Controls\GridViewEx.cs:行号 454
   在 Admin_06_Admin_TextSite.Page_Load(Object sender, EventArgs e) 位置 d:\SenateManages\Admin\06\Admin_TextSite.aspx.cs:行号 36
   在 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
   在 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
   在 System.Web.UI.Control.OnLoad(EventArgs e)
   在 System.Web.UI.Control.LoadRecursive()
   在 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)怎么解决啊？
public partial class Admin_06_Admin_TextSite : System.Web.UI.Page
{
    public static string OperType;
    clsLogic clsLogic1 = new clsLogic();
    ClsDbOper ClsDbOper1 = new ClsDbOper();
    protected void Page_Load(object sender, EventArgs e)
    {
        ClsCommon.ChkLogin(Session["UserId"]);
        if (!IsPostBack)
        {
            lblTitle.Text = "考场信息维护";
            clsLogic1.GetOperGroup(Session["GroupId"], Session["UserId"], "考场信息", btnAdd, "添加");
            clsLogic1.GetOperGroup(Session["GroupId"], Session["UserId"], "考场信息", btnQuery, "查询");
            clsLogic1.GetOperGroup(Session["GroupId"], Session["UserId"], "考场信息", btnExport, "导出");
            
            
            //绑定教室名称
            string sql = "select JID,JName from T_Info_Classroom";
            clsLogic1.InitDdlbySql(sql, ddlCID);
            OperType = "1=2";
            GridView1.OnBind();
        }
    }
    protected void GetBin()
    {
        try
        {
            string sql = "SELECT a.ExamRoomId  ,T_Info_Classroom.JName,a.ExamPer,a.SelectPer,a.Operator,a.OperDate,a.Re FROM T_Info_ExamRoom a  left join T_Info_Classroom  on T_Info_Classroom.JID = a.ClassRoom where " + OperType + " ";
            if (ddlCID.SelectedValue == "0")
            {
                sql += " and a.ClassRoom ='" + ddlCID.SelectedValue.ToString() + "'";
            }
            if (txtDName.Text != "")
            {
                sql += " and T_Info_Classroom.JName like '%" + txtDName.Text.Trim() + "%'";
            }
            sql += " ORDER BY a.ExamRoomId desc";            DataTable dt = ClsDbOper1.GetDataTable(sql);
            GridView1.DataSource = dt;
        }
        catch (Exception ex)
        {
            Response.Redirect("../ErrorMsg.aspx?ErrId=query&ErrMsg=" + ex.Message);
        }
    }