我可以从try-catch的catch块中删除e吗？

Question

catch (HttpAntiForgeryException e)
{
    throw new HttpAntiForgeryException("Forgery Exception");
}

When I build the project, there is a warning said: The variable 'e' is declared but never used. Is that because the e is not necessary?

Answer 1

Yes. You can just simply write

catch (HttpAntiForgeryException)
{
    throw new HttpAntiForgeryException("Forgery Exception");
}

But, you are rethrowing same type of exception. You can also simply delete this catch block.

Answer 2

It is no necessary if you don't want to do anything with the exception, in your case you are throwing custom message so its fine to use like this :

catch 
{
   throw new HttpAntiForgeryException("Forgery Exception");
}

or like this :

// For specific exception
catch (HttpAntiForgeryException)
{
       throw new HttpAntiForgeryException("Forgery Exception");
}

But you will not get any information regarding this exception, like error message, stack-Trace, inner exception etc.. I prefer you to handle the exception in Catch, Or properly log them for developer's reference

Answer 3

It's because You have not used the Variable e within any where of the catch block. You can easily catch that exception so you will get better understanding of the root cause of your exception than throwing a new exception.

catch (HttpAntiForgeryException e)
{
    Console.WriteLine(e.Message); // Console.Writeline or whichever way you want      
}