asp.net登录页面代码 [英] asp.net login page code

问题描述

在第26行显示错误.

its showing error in line number 26..

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Configuration;

public partial class home : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["RegconnectionString"].ConnectionString);
        con.Open();
        string cmdStr = "Select Count(*) from Registration where UserName='" + TextBox1.Text + "'";
        SqlCommand Checkuser = new SqlCommand(cmdStr, con);
        int temp = Convert.ToInt32(Checkuser.ExecuteScalar().ToString());
        if (temp == 1)
        {
            string cmdstr2 = "Select Password from Registration where UserName='" + TextBox1 + "'";
            SqlCommand pass = new SqlCommand(cmdstr2, con);
            string password = pass.ExecuteScalar().ToString();
            con.Close();
            if (password == TextBox2.Text)
            {
                Session["New"] = TextBox1.Text;
                Response.Redirect("gallery.aspx");
            }
            else
            {
                Label1.Visible = true;
                Label1.Text = "Invalid Password...!!!";
            }
        }
        else
        {
            Label1.Visible = true;
            Label1.Text = "Invalid UserName...!!!";
        }
    }
}

推荐答案

嗨.
"pass.ExecuteScalar()"的结果可能为空值.
您不能调用null的ToString()方法.

hi.
the result of "pass.ExecuteScalar()" may be a null value.
You can''t call ToString() method of a null.

object password = pass.ExecuteScalar();
if (password != null)
{
    //here you can use password
}

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