请教该语句为什么出错LabelBianji.Text = Session["LoginName"].ToString();

using System;using System.Data;using System.Configuration;using System.Collections;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;using System.Data.SqlClient;public partial class BianJi_OpinionBianJi : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { LabelBianji.Text = Session["LoginName"].ToString(); SqlDataReader dr = Paper.GetPaperMessageByNumber(Convert.ToInt32(Request.QueryString["Number"].ToString())); if (dr.Read()) { TextBox1Title.Text = dr["Head"].ToString(); TextBoxAssTitle.Text = dr["AssistantHead"].ToString(); TextBoxKeyWorld.Text = dr["KeyWord"].ToString(); DropDownListPaperStype.SelectedValue = dr["Speciality"].ToString(); TextBoxCommentMan.Text = dr["CommendMan"].ToString(); TextBoxSummary.Text = dr["Summary"].ToString(); TextBoxEnglishSummary.Text = dr["EnglishSummary"].ToString(); TextBoxRemark.Text = dr["Remark"].ToString(); HyperLinkPaperContent.Text = dr["Head"].ToString(); HyperLinkPaperContent.NavigateUrl = dr["PaperContent"].ToString(); } } } protected void ButtonOK_Click(object sender, EventArgs e) { if(Paper.InseretOpinionByNumber(Convert.ToInt32(Request.QueryString["Number"].ToString()),Session["LoginName"].ToString(),TextBoxOpinion.Text)) { Paper.InseretPaperIdByNumber(Convert.ToInt32(Request.QueryString["Number"].ToString()),Session["LoginName"].ToString()); } if(Paper.UpdateYiShen(Convert.ToInt32(Request.QueryString["Number"].ToString()))) { LabelResult.Text="提交稿件意见成功，谢谢你审稿！"; } }