CODEWITHSUNDEEP
c#exceptiontry-catchthrow
John
John

Reputation: 47

Is there a reason to throw an exception twice?

Debugging production code I came across something I had not seen before and am not aware of a valid purpose. In several methods of one of our controllers we have try-catch blocks. The interesting part is there are 2 throw statements in one of the catches.

Is there any reason to have 2 throw statements? If so, in what circumstance(s) does that make sense?

        try
        {
           //statements
        }
        catch (SoapException se)
        {
            //Log statement
            return null;
        }
        catch (Exception ex)
        {
            //Log statement
            throw;
            throw;
        }

Upvotes: 2

Views: 1631

Answers (3)

Nick Freeman
Nick Freeman

Reputation: 1411

No there is no reason to throw twice. The second throw will never be reached.

It is also similar to having 

public int GetNumber()
{
    return 1;
    return 2; // Never reached
}

Update

Resharper is a great tool to check things like this.

In this case it will grey out the second throw and tell you it is unreachable.

enter image description here

Upvotes: 10

eandersson
eandersson

Reputation: 26362

There is absolutely no purpose in throwing an exception twice in a row. The second throw can never be reached, and it is most likely a typo, or code that was edited, but never completed and since forgotten about.

Upvotes: 3

duckbrain
duckbrain

Reputation: 1279

In the example you showed, there would be no purpose to the two throw statements. As soon as the first one is hit it starts to work its way back up the call stack until it is caught. The only way for two to make any differance is if the first one was conditional or caught before he second one was hit.

    try
    {
       //statements
    }
    catch (SoapException se)
    {
        //Log statement
        return null;
    }
    catch (Exception ex)
    {
        //Log statement
        if (condition)
            throw;
        throw;
    }

or

    try
    {
       //statements
    }
    catch (SoapException se)
    {
        //Log statement
        return null;
    }
    catch (Exception ex)
    {
        //Log statement
        try
        {
             throw;
        }
        catch (Exception)
        {
             //Handle first thrown exception.
        }
        throw;
    }

Upvotes: 3

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