未将对象引用设置到对象的实例
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;
using System.IO;
public partial class UserWork_Bottom : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string status="未读";
string Name = SelectName();
SqlConnection con=new SqlConnection(ConfigurationManager.AppSettings["Connection"]);
con.Open();
string sql = "select * from Email,Employee where Email.Meetname='" + Name + "' and status='" + status + "' ";
SqlCommand com = new SqlCommand(sql,con);
SqlDataReader dr = com.ExecuteReader();
if (dr.Read())
{
Response.Write("<bgsound src='D:\\OA_Test\\你有新的消息，请注意查收！hun(NEW59).mp3' autostart='true'>");
}
con.Close();
if (!IsPostBack)
{
Bind();
}
}
protected void bnQuery_ServerClick(object sender, EventArgs e)
{
}
public void Bind()
{
SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["Connection"]);
con.Open();
string Name=SelectName();
string sql = "select * from Email,Employee where Email.Meetname='" + Name + "' and Email.sendname=Employee.username order by sid desc ";
SqlDataAdapter da = new SqlDataAdapter(sql,con);
DataSet ds = new DataSet();
da.Fill(ds);
GridView1.DataSource = ds;
GridView1.DataBind();
//while (dr.Read())
//{
// string Meetname = dr["Meetname"].ToString();
// string[] a;
// a = Meetname.Split(';');
// for (int i = 0; i < a.Length; i++)
// {
// string c = a[i].ToString();
// string b = ChaXun();
// if (c == b)
// {
// }
// }
//}
//con.Close();
}
public string SelectName()
{
SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["Connection"]);
con.Open();
string sql = "select Name from Employee where username='"+Session["UserName"].ToString()+"'";
SqlCommand com = new SqlCommand(sql,con);
SqlDataReader dr = com.ExecuteReader();
dr.Read();
string Name = dr.GetValue(0).ToString();
return Name;
}
protected void bnQuery_ServerClick1(object sender, EventArgs e)
{
if (this.txFDate.Value == "" || this.txTDate.Value == "")
{
Response.Write("<script>alert('请选择时间！')</script>");
}
else
{
DateTime FD = Convert.ToDateTime(this.txFDate.Value);
DateTime TD = Convert.ToDateTime(this.txTDate.Value);
SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["Connection"]);
con.Open();
string sql = "select * from Email,Employee where Pubdate between '" + FD + "' and '" + TD + "' and sendname='" + Session["UserName"].ToString() + "' and Email.sendname=Employee.username";
SqlDataAdapter da = new SqlDataAdapter(sql, con);
DataSet ds = new DataSet();
da.Fill(ds);
GridView1.DataSource = ds;
GridView1.DataBind();
this.Label1.Text = "共" + ds.Tables[0].Rows.Count + "记录";
con.Close();
}
}
protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{
SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["Connection"]);
con.Open();
int sid = Convert.ToInt32(GridView1.DataKeys[e.NewEditIndex].Value.ToString());
string status = "已查看";
string sql = "update Email set Status='"+status+"' where sid="+sid+" ";
SqlCommand com = new SqlCommand(sql,con);
com.ExecuteNonQuery();
con.Close();
Response.Redirect("../MailRead1.aspx?sid="+sid+"");
}
protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["Connection"]);
con.Open();
int sid = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value.ToString());
string sql = "select Appurtenance from Email where sid=" + sid + "";
SqlCommand com = new SqlCommand(sql,con);
SqlDataReader dr = com.ExecuteReader();
dr.Read();
string ss=dr["Appurtenance"].ToString();
string[] a = ss.Split(';');
string url = "";
for (int i = 0; i < a.Length; i++)
{
string b = a[i];
url = Server.MapPath("~") + "\\upfiles\\" + b;
break;
}
if(File.Exists(url))
{
File.Delete(url);
}
SqlConnection con1 = new SqlConnection(ConfigurationManager.AppSettings["Connection"]);
con1.Open();
string sql1 = "delete from Email where sid=" + sid + "";
SqlCommand com1 = new SqlCommand(sql1, con1);
com1.ExecuteNonQuery();
Response.Write("<script>alert('删除成功！')</script>");
con1.Close();
Bind();
}
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
if (e.Row.RowState == DataControlRowState.Normal || e.Row.RowState == DataControlRowState.Alternate)
{
((LinkButton)e.Row.Cells[6].Controls[0]).Attributes.Add("onclick", "javascript:return confirm('你确认要删除吗?')");
}
}
}
}
错误提示：string sql = "select Name from Employee where username='"+Session["UserName"].ToString()+"'";
——>用户代码为处理NullReferenceException 未将对象引用设置到对象的实例
麻烦各位高手帮忙。 --------------------编程问答-------------------- Session["UserName"]没有 --------------------编程问答-------------------- 你用ToString()方法时,首先要检查页面中Session["UserName"]是否为空,如果为空就会报这个错的 --------------------编程问答-------------------- 说明你这个Session["UserName"]为空啊 --------------------编程问答-------------------- Session["UserName"]==null?"":Session["UserName"].ToString() --------------------编程问答-------------------- 怎样检查页面中Session["UserName"]是否为空？ --------------------编程问答-------------------- 我是新手，有很多不懂，正在做毕业设计，有点急 --------------------编程问答-------------------- Session["UserName"] == null
这个就可以了 --------------------编程问答-------------------- 这种情况多是没有声明变量，突然出现了调用
或者变量不是全局的
很多ASP.net初学者都以为Page_Load方法是万能的 --------------------编程问答-------------------- string sql = "select Name from Employee where username='"+Session["UserName"]==null?"":Session["UserName"].ToString()+"'"; --------------------编程问答-------------------- string sql = "select Name from Employee where username='"+Session["UserName"]==null?"":Session["UserName"].ToString()+"'";
我用这种方法，还是提示同样的错误，叫高手继续指点，谢谢！ --------------------编程问答-------------------- 单步看哪里出错 --------------------编程问答-------------------- 怎样单步？我还没有听说过呢 --------------------编程问答-------------------- 设断点调试。。
F9设断点
F10跟踪
--------------------编程问答-------------------- 走单步呀，有可能读数据库的时候就没有引用出来
补充：.NET技术 , ASP.NET
