C＃重新拋出異常的設計來處理異常和保存堆棧跟蹤

Question

我想寫一個處理異常的方法，這將被稱爲catch塊內的方法。根據通過的異常類型，異常無論是作爲一個新的異常的內部異常傳遞或者乾脆重新拋出。如何在第二種情況下保留堆棧跟蹤？

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，因爲該模式是重複的很多地方，不會有分解：

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

Answer 1

您需要使用throw無指定例外以保留堆棧跟蹤。這隻能在catch塊內進行。你能做的是從HandleException返回，沒有拋出原來的異常，然後使用throw權算賬：

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進行分類外，首選的方法是二catch塊：

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讓例外告吹：

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

也許你可以試試這個。

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

Answer 3

事實上，有使用System.Runtime.ExceptionServices.ExceptionDispatchInfo.Capture在.Net4.5這樣做的一個非常好的方式：

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(); 
    } 
}