C# throw vs throw ex

新手经常区分不清楚throw 跟 throw ex 有什么区别，在一些遗留代码中我们也经常能见到类似的错误用法。

一句话总结：throw ex 会重置调用栈，而throw不会。绝大多数情况我们都不希望调用栈被重置，这样不利于定位问题。

下面做一个简单的测试：

 1 namespace SimpleConsole
 2 {
 3     internal class ExceptionTest
 4     {
 5         public void Test()
 6         {
 7             try
 8             {
 9                 Method1();
10             }
11             catch (Exception ex)
12             {
13                 Console.WriteLine(ex.Message);
14                 Console.WriteLine(ex.StackTrace);
15             }
16 
17             Console.WriteLine("#################################################");
18 
19             try
20             {
21                 Method2();
22             }
23             catch (Exception ex)
24             {
25                 Console.WriteLine(ex.Message);
26                 Console.WriteLine(ex.StackTrace);
27             }
28         }
29 
30         public void Method1()
31         {
32             try
33             {
34                 ThrowException("Method 1");
35             }
36             catch (Exception ex)
37             {
38                 throw ex;
39             }
40         }
41 
42         public void Method2()
43         {
44             try
45             {
46                 ThrowException("Method 2");
47             }
48             catch (Exception ex)
49             {
50                 throw;
51             }
52         }
53 
54         private void ThrowException(string msg)
55         {
56             throw new Exception("Exception from " + msg);
57         }
58     }
59 }