C＃重新抛出异常的设计来处理异常和保存堆栈跟踪

Question

我想写一个处理异常的方法，这将被称为catch块内的方法。根据通过的异常类型，异常无论是作为一个新的异常的内部异常传递或者干脆重新抛出。如何在第二种情况下保留堆栈跟踪？

例子：

public void TestMethod() 
{ 
    try 
    { 
     // can throw an exception specific to the project or a .Net exception 
     SomeWorkMethod() 
    } 
    catch(Exception ex) 
    { 
     HandleException(ex); 
    } 
} 

private void HandleException(Exception ex) 
{ 
    if(ex is SpecificException) 
     throw ex; //will not preserve stack trace... 
    else 
     throw new SpecificException(ex); 
} 

我不希望做的是，因为该模式是重复的很多地方，不会有分解：

try 
{ 
    SomeWorkMethod(); 
} 
catch(Exception ex) 
{ 
    if(ex is SpecificException) 
     throw; 
    else 
     throw new SpecificException(ex); 
} 

Answer 1

您需要使用throw无指定例外以保留堆栈跟踪。这只能在catch块内进行。你能做的是从HandleException返回，没有抛出原来的异常，然后使用throw权算账：

public void TestMethod() 
{ 
    try 
    { 
     // can throw an exception specific to the project or a .Net exception 
     SomeWorkMethod() 
    } 
    catch(Exception ex) 
    { 
     HandleException(ex); 
     throw; 
    } 
} 

private void HandleException(Exception ex) 
{ 
    if(ex is SpecificException) 
     return; 
    else 
     throw new SpecificException(ex); 
} 

只要您只使用is进行分类外，首选的方法是二catch块：

public void TestMethod() 
{ 
    try 
    { 
     // can throw an exception specific to the project or a .Net exception 
     SomeWorkMethod() 
    } 
    catch (SpecificException) 
    { 
     throw; 
    } 
    catch(Exception ex) 
    { 
     throw new SpecificException(ex); 
    } 
} 

用C＃6.0，你也可以使用when让例外告吹：

public void TestMethod() 
{ 
    try 
    { 
     // can throw an exception specific to the project or a .Net exception 
     SomeWorkMethod() 
    } 
    catch(Exception ex) when (!(ex is SpecificException)) 
    { 
     throw new SpecificException(ex); 
    } 
} 

Answer 2

也许你可以试试这个。

if(ex.Gettype() == typeof(SpecificException)) 

Answer 3

事实上，有使用System.Runtime.ExceptionServices.ExceptionDispatchInfo.Capture在.Net4.5这样做的一个非常好的方式：

void Main() 
{ 
    try 
    { 
     throw new Exception(); //appears to be thrown from here 
    } 
    catch(Exception ex) 
    { 
     ThrowEx(ex); 
    } 

} 
public void ThrowEx(Exception ex) 
{ 
    if(someCondition) 
    { 
     //we're in the scope of a `catch` and the exception 
     //is "active", so the exception with original stack-trace 
     //can be re-thrown with 
     ExceptionDispatchInfo.Capture(ex).Throw(); 
     //the following line is unreachable, but the compiler doesn't realise 
     //so we can "tell" the compiler that this branch ends in an exception 
     //and avoid having to return anything in the non-void case 
     throw new Exception(); 
    } 
}