我该如何解决这个请帮助我。 [英] How Do I Solve This Please Help Me.

问题描述

Error:System.NullReferenceException: Object reference not set to an instance of an object. at Samregistration.Button1_Click(Object sender, EventArgs e)<br />

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Security.Cryptography;
using System.Text;
using System.Configuration;
using System.Data;

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

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        try
{
       SqlConnection conn= new SqlConnection (ConfigurationManager.ConnectionStrings["Data Source=SUMIT92\\SQLEXPRESS;Initial Catalog=Registration1.dbo;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"].ConnectionString);
        conn.Open();
        string insertQuery ="insert into Regstration2 (UserName,E-mail,Password,Country) values (@Uname,@email,@password,@country)";
        SqlCommand com = new SqlCommand (insertQuery, conn);
        com.Parameters.AddWithValue("@Uname", TextBoxUN.Text);
            com.Parameters.AddWithValue("@email",TextBoxEM.Text);
            com.Parameters.AddWithValue("@password",TextBoxp.Text);
            com.Parameters.AddWithValue("@country",CN.SelectedItem.ToString());

            com.ExecuteNonQuery();
            Response.Write("Registration is sucessfull");

            conn.Close();
        }
        catch (Exception ex)
        {
          Response.Write("Error:"+ex.ToString());
        }
    }
}

推荐答案

看起来你正在尝试使用整个连接字符串作为连接字符串的键。当您在 ConfigurationManager.ConnectionStrings 上调用索引时，我希望您应该传递一个名称/密钥来标识配置中的连接字符串，但是您正在通过整个连接字符串作为名称/键。



尝试更改

It looks like you're trying to use the entire connection string as a key to a connection string. When you call the indexed on ConfigurationManager.ConnectionStrings I would expect that you're supposed to pass a name/key that identifies a connection string in the config, but you're passing the entire connection string as name/key.

Try changing

SqlConnection conn= new SqlConnection (ConfigurationManager.ConnectionStrings["Data Source=SUMIT92\\SQLEXPRESS;Initial Catalog=Registration1.dbo;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"].ConnectionString);

to

to

SqlConnection conn= new SqlConnection ("Data Source=SUMIT92\\SQLEXPRESS;Initial Catalog=Registration1.dbo;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"]);

希望这会有所帮助，

Fredrik

Hope this helps,
Fredrik

最佳猜测 - 组合框中没有选定的项目，因此它在此行上失败：

Best guess - no selected item in the combo box, so it fails on this line:

com.Parameters.AddWithValue("@country",CN.SelectedItem.ToString());

检查方法顶部的值，确保在尝试转到数据库之前所有用户输入都有效。例如：输入的用户名是？它有独特之处吗？是否有电子邮件，是否为有效格式？



此外：

1）您的连接字符串名称不应相同作为连接字符串：

Check your values at the top of the method and make sure that all the user inputs are valid before you even try to go to the database. For example: is the username entered? Is it unique? Is there an email, and is it a valid format?

In addition:
1) Your connection string name should not be the same as the connection string:

SqlConnection conn= new SqlConnection (ConfigurationManager.ConnectionStrings["Data Source=SUMIT92\\SQLEXPRESS;Initial Catalog=Registration1.dbo;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"].ConnectionString);

Shoudl有点像：

Shoudl be somethign like:

SqlConnection conn= new SqlConnection (ConfigurationManager.ConnectionStrings["Registration"].ConnectionString);

。

2）您应该处理Connection和Command对象 - 如果出现问题，您的代码会保持连接处于打开状态，因为您没有将其关闭 catch 块。考虑使用使用块来确保在完成对象时始终销毁对象：

.
2) You should Dispose of Connection and Command objects - your code leaves the connection open if there is a problem because you don't close it in the catch block. Consider using a using block to ensure objects are always destroyed when you are finished with them:

try
   {
   using (SqlConnection conn= new SqlConnection (ConfigurationManager.ConnectionStrings["Registration"].ConnectionString))
       {
       conn.Open();
       string insertQuery ="insert into Regstration2 (UserName,E-mail,Password,Country) values (@Uname,@email,@password,@country)";
       using (SqlCommand com = new SqlCommand (insertQuery, conn))
           {
           com.Parameters.AddWithValue("@Uname", TextBoxUN.Text);
           com.Parameters.AddWithValue("@email",TextBoxEM.Text);
           com.Parameters.AddWithValue("@password",TextBoxp.Text);
           com.Parameters.AddWithValue("@country",CN.SelectedItem.ToString());

           com.ExecuteNonQuery();
           Response.Write("Registration is sucessfull");
           }
       }
   }
   catch (Exception ex)
       {
       Response.Write("Error:"+ex.ToString());
       }

3）请不要以明文形式存储密码 - 这是一个主要的安全风险。有关如何在此处执行此操作的信息：密码存储：如何做到这一点。 [ ^ ]

另见：代码犯罪：基于文本的密码 [ ^ ]

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