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Difference: throw or throw ex?

發布時間：2023/12/10 编程问答 31 豆豆

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Difference: throw or throw ex?

主要區別在于throw出的堆棧詳細程度。

throw ex只是拋出在當前代碼處的錯誤。

throw 能夠更進一步，拋出內部調用的具體錯誤。

Just for demonstrating, if you have classes in C#?as follows:

using System;namespace WindowsApplication2 {public class Class1{public static void DoSomething(){try{Class2.DoSomething(); }catch(Exception ex){throw ex;}}}public class Class2{public static void DoSomething(){try{Class3.DoSomething(); }catch(Exception ex){throw ex;}}}public class Class3{public static void DoSomething(){try{int divider=0;int number=5/divider;}catch(Exception ex){throw ex;}}} }

And you call:

Class1.DoSomething();

What's the difference if you rethrow the exception using plain 'throw;' or 'throw ex;'?

ANSWER:

If you use "throw ex;", The stack trace is something like:

System.DivideByZeroException: Attempted to divide by zero.
?? at WindowsApplication2.Class1.DoSomething() in l:\vs.net-projektit\windowsapplication2\main.cs:line 15
?? at WindowsApplication2.Form1.button1_Click(Object sender, EventArgs e) in l:\vs.net-projektit\windowsapplication2\form1.cs:line 103

But if you use just 'throw' instead of 'throw ex' to rethrow the same?exception, that is:

public class Class3{public static void DoSomething(){try{int divider=0;int number=5/divider;}catch{throw ;}}}

And?of course for all rethrow statements, the stack trace is now?like:

System.DivideByZeroException: Attempted to divide by zero.
?? at WindowsApplication2.Class3.DoSomething() in l:\vs.net-projektit\windowsapplication2\main.cs:line 46
?? at WindowsApplication2.Class2.DoSomething() in l:\vs.net-projektit\windowsapplication2\main.cs:line 30
?? at WindowsApplication2.Class1.DoSomething() in l:\vs.net-projektit\windowsapplication2\main.cs:line 15
?? at WindowsApplication2.Form1.button1_Click(Object sender, EventArgs e) in l:\vs.net-projektit\windowsapplication2\form1.cs:line 103

See the difference??BTW: This concerns both C# and VB. VB docs state that in "Throw?expression" the?expression?would be required. This is not completely true, you can use just "Throw" in VB?to rethrow the same?exception. C# docs do tell that in "throw?expression" the?expression?"is omitted when rethrowing the current exception object in a catch clause".

本文轉自cnn23711151CTO博客，原文鏈接：http://blog.51cto.com/cnn237111/508446?，如需轉載請自行聯系原作者

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