重新拋出異常是這種情況下

Question

我有這樣的事情：

public byte[] AnyMethod(){ 

    try { 
    ... 
    } 
    catch (Exception e) { 
    string errorMessage = 
     "Some custom message, which should the caller of that method should receive"; 

    // I thought something of this ,to pass through my custom exception to the caller?! 
    throw new ApplicationException(errorMessage); 

    //but this does not allow the method 
    } 

} 

但這：

throw new ApplicationException(errorMessage); 

會導致：

類型的異常「System.ApplicationException '發生在... dll但未在用戶代碼中處理

如何給我的上述方法的調用者提供自定義錯誤消息？

Answer 1

首先，使用自定義異常或至少一個更有意義的，而不是ApplicationException。其次，如果你的方法拋出它，你必須捕獲異常。

所以調用的方法也應包裹方法調用的try...catch：

try 
{ 
    byte[] result = AnyMethod(); 
}catch(MyCustomException ex) 
{ 
    // here you can access all properties of this exception, you could also add new properties 
    Console.WriteLine(ex.Message); 
} 
catch(Exception otherEx) 
{ 
    // all other exceptions, do something useful like logging here 
    throw; // better than throw otherEx since it keeps the original stacktrace 
} 

下面是一個抽象的，簡化的例子：

public class MyCustomException : Exception 
{ 
    public MyCustomException(string msg) : base(msg) 
    { 
    } 
} 

public byte[] AnyMethod() 
{ 
    try 
    { 
     return GetBytes(); // exception possible 
    } 
    catch (Exception e) 
    { 
     string errorMessage = "Some custom message, which should the caller of that method should receive"; 
     throw new MyCustomException(errorMessage); 
    } 
} 

但請注意，你不應該使用正常程序例外流。相反，您可以返回true或false來指示操作是否成功或對byte[]（如int.TryParse（或其他TryParse方法））使用out parameter。

Answer 2

publy byte[] AnyMethod(){ 

try{ 


}catch(Exception e){ 

    string errorMessage = string.Format("Some custom message, which should the caller of that method should receive. {0}", e); 

    //I thought something of this ,to pass through my custom exception to the caller?! 
    throw new ApplicationException(errorMessage); 
    //but this does not allow the method 
    } 

    } 

OR

public byte[] AnyMethod(){ 

try{ 


}catch(Exception e){ 

string errorMessage = "Some custom message, which should the caller of that method should receive"; 

//I thought something of this ,to pass through my custom exception to the caller?! 
throw new ApplicationException(errorMessage, e); 
//but this does not allow the method 
} 

}