“对象引用未设置为对象的实例”在使用c＃进行单元测试？ [英] "Object Reference not set to an instance of an object" in unit testing using c#?

问题描述

我要对我的项目进行单元测试，但它显示错误为对象引用没有设置为对象的实例。有人给我一个解决这个问题的方法。

我在这个项目中引用了所有必需的命名空间。

  //  单元测试代码 
 
 使用系统; 
 
 使用 Microsoft.VisualStudio.TestTools.UnitTesting; 
 
 
 使用 Software.Test; 
 
 
 命名空间 UnitTestProject 
 {
 
 [TestClass] 
 
  public   class  UnitTest1 
 {
 
 [TestMethod] 
 
  public   void  TestMethod1（）
 {
 ConnectionTests .TestConnection（  https://sample.com）; 
 
 Guid id = ConnectionTests.TestConnectionSettings（  https://sample.com， 示例测试，  customer_name，  xyzasd） ; 
 
} 
} 
} 
 
 
 
 
  / /  用于单元测试的项目 
 
 命名空间 Software.TestClient 
 {
 
  public   static  类 ConnectionTests 
 {
 
  public   static   void  TestConnection（ string  Url）
 {
来源Con = 空; 
 appGlobal.AddText（）; 
 appGlobal.AddText（ 正在连接 + Url +   ...）; 
 Con = Source.Open（Url）; 
} 
 
} 
 
 
  public   static  Guid TestConnectionSettings（ string  Url， string 名称，字符串客户，字符串密钥）
 {
 ConnectionDetails det =  new  ConnectionDetails（）; 
 
 det.data =  ; 
 det.url = Url; 
 
 
 使用（Software.Client.Source src = Software.Client.Source.Open（Url））
 {
 src.StartConnection（key，Name）; 
 
} 
 
} 

谢谢

Karthik.R

解决方案

我认为它可能在TestConnection方法中的Source Con上。

来源Con =  null ; 
 

不能抛出空引用异常 - 它不引用或创建任何类的实例。

然而，下一行可能是：

 appGlobal.AddText（）; 
 

检查你对appGlobal的引用 - 名称上的情况意味着它是一个变量，如果你还没有为它赋值，那么你将获得一个空引用异常。 / blockquote>

您没有显示带有对象引用未设置为对象实例消息的异常的位置。每次遇到这个小问题时，都不应该问一个具体的问题。在所有情况下学习如何自己处理所有这些非常重要。



不用担心。这是检测和修复的最简单的案例之一。它只是意味着某些引用类型的某个成员/变量通过使用和它的实例（非静态）成员解除引用，这要求此成员/变量为非null，但实际上它似乎为null。只需在调试器下执行它，它将停止抛出异常的执行。在该行上设置一个断点，重新启动应用程序并再次到达这一点。评估下一行中涉及的所有引用，并查看哪一个为null，而不需要为null。解决这个问题之后，修复代码：要么确保将成员/变量正确初始化为非空引用，要么将其检查为null，如果为null，则执行其他操作。



另请参阅：想要在按钮点击时显示下一条记录。但是如果下一条记录功能的条件对象引用没有设置为对象的实例 [ ^ ]。



有时候，你不能在调试器下，由于一个或另一个原因做到这一点。一个非常讨厌的情况是，只有在调试信息不​​可用时构建软件时才会出现问题。在这种情况下，你必须使用更难的方式。首先，你需要确保你永远不会通过静默处理异常来阻止异常的传播（这是开发人员对自己的犯罪，但很常见）。您需要在每个线程的最顶层堆栈帧上捕获绝对所有异常。如果处理类型 System.Exception 的异常，则可以执行此操作。在处理程序中，您需要记录所有异常信息，尤其是 System.Exception.StackTrace ：

http://msdn.microsoft.com/en-us/library/system.exception.aspx [ ^ ]，

http://msdn.microsoft.com/en-us/library/system.exception。 stacktrace.aspx [ ^ ]。



堆栈跟踪只是一个字符串，显示从throw语句到处理程序的异常传播的完整路径。通过阅读，您总能找到目的。对于日志记录，使用类 System.Diagnostics.EventLog ：

http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx [ ^ ]。

-SA

Hi,
I am tring to unit test my project but it showing error as "Object Reference not set to an instance of an object". someone kindly give me a solution for this problem.
I referred all necessary namespace in this project.

//Unit Test code

using System;

using Microsoft.VisualStudio.TestTools.UnitTesting;


using Software.Test;


namespace UnitTestProject
{

    [TestClass]

    public class UnitTest1
    {

        [TestMethod]

        public void TestMethod1()
        {
           ConnectionTests.TestConnection("https://sample.com");

           Guid id = ConnectionTests.TestConnectionSettings("https://sample.com", "Sample Test", "customer_name", "xyzasd");

        }
    }
}


   

 //Project used for unit testing
   
namespace Software.TestClient
{
   
    public static class ConnectionTests
    {
       
        public static void TestConnection(string Url)
        {
           	Source Con = null;
                appGlobal.AddText();
                appGlobal.AddText("Connecting " + Url + "...");
                Con = Source.Open(Url);
         }
           
     }


        public static Guid TestConnectionSettings(string Url, string Name, string customer, string Key)
        {
            ConnectionDetails det= new ConnectionDetails();
          
            det.data = "";
            det.url = Url;
           
           
                using (Software.Client.Source src = Software.Client.Source.Open(Url))
                {
                    src.StartConnection(key,Name);

                }
               
        }

Thanks
Karthik.R

解决方案

"i think it may be on "Source Con" in TestConnection method. "

Source Con = null;

Can't throw a null reference exception - it doesn't refer to or create an instance of any class.
However, then next line is likely to:

appGlobal.AddText();

Check your references to appGlobal - the case on the name implies it is a variable, and if you haven't assigned a value to it yet then you will get a null reference exception.

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown. You should not ask a specific question each time you face this little problem. It's much more important to learn how to deal with it all by yourself in all cases.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object"[^].

Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx[^],
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx[^].

The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx[^].

Good luck,

—SA

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