NULL参考异常是未处理的 [英] NULL REFERENCE EXCEPTION WAS UNHANDLED

问题描述

我创建了一个app.config文件并将数据源放在那里，因为它在不久的将来会发生变化，并且我一直得到空引用异常未处理。



使用new关键字作为对象实例



但我已经导入了使用系统。配置



但仍然。我试图赶上但似乎没有工作

I created an app.config file and put the datasource in there incase it changes in the near future and i keep getting the null reference exception was unhandled.

use the new keyword as an object instance

but i have already imported the using system.configuration

and yet still. i have tried to catch but it seems not to work

public partial class LoginForm : Form
    {
        //Main mnFrm;
        SqlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["DbConn"].ToString());//the exception is thrown on this line when I run the program
        
        SqlDataReader sdr;
        SqlCommand sqlCmd = new SqlCommand();

        public LoginForm(Main mnFrm)
        {
            //this.mnFrm = mnFrm;
            InitializeComponent();
        }

我将非常感谢帮助人员提前感谢

I would appreciate the help guys thanks in advance

推荐答案

请参阅：如何获取c＃中App.Config的连接字符串 [ ^ ]。



另请查看：

MSDN：存储和检索连接字符串 [ ^ ]

在App.Config文件中配置连接字符串在运行时期间对于C＃Windows应用程序 [ ^ ]

- Amit

Please see : How to get Connection String from App.Config in c#[^].

Also check :
MSDN : Storing and Retrieving Connection Strings [^]
Configuring Connection String in App.Config File During Runtime For a C# Windows Application[^]

--Amit

qlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["DbConn"].ToString());//the exception is thrown on this line when I run the program

你写的这行中的
你的配置文件中不存在密钥DbConn你是否在那里写错了。

in this line you write Key "DbConn" dose not exist in your config file are you write wrong spell there.

您的配置文件的ConnectionStrings部分中是否有名为DbConn的连接？

Do you have a connection called "DbConn" in the ConnectionStrings section of your config file?

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