How would you go about catching the overflow exception Jeremy talks about in the end of the video ?

Question

Hi all, thanks for taking a look at this !

I am curious if you have to add another Try or just another Catch inside the same class ?

For example here is my code:

catch(FormatException)
                {
                  Console.WriteLine("Please use numbers or \"quit\" for the program to work");
                  continue;
                }

Would this be correct to just add at the end of my code?

catch(FormatException)
                {
                  Console.WriteLine("Please use numbers or \"quit\" for the program to work");
                  continue;
                } 
catch(OverflowException)
                {
                  Console.WriteLine("Please use numbers or \"quit\" for the program to work");
                  continue;
                }

Not sure what kind of numbers I would have to get to trigger the exception but when I spam a bunch of 9's the console returns this number : 1E+72 , I am no good at math so maybe the overflow is just very very very large? Maybe don't worry about triggering it ?

Thanks!

Answer 1 · 2017-02-04T02:30:56Z

February 4, 2017 2:30am

You don't need multiple try/catch blocks, your guess that you can define multiple catch blocks for a single try block is correct. The code you show in your example is completely valid.

The only thing you need to be aware of is that is that the catch blocks has to be sorted in such a way that one catch block won't catch an exception that a catch block below it was meant to catch. If you use a catch block to catch exceptions of type Exception for example (which is the exception class all exceptions inherit from) then that block would catch all exceptions. If you placed that at the top then any more specific catch blocks down below would never execute since the first catch block would always catch the exception.

The C# compiler will actually refuse to compile your code in such a situation. If you place the Exception catch block as the last one though then it won't be a problem, since the more specific catch blocks will end up catching the exception first.

Answer 2 · 2017-02-04T16:40:17Z

February 4, 2017 4:40pm

If you want to catch an OverflowException for an arithmetic operation you need to use the checked keyword on the block of code that you expect the exception to be raised. Then you can attempt to catch it. This is necessary because the compiler does not perform overflow checks on arithmetic by default and insteads wraps the operation around the minimum or maximum value of the type.

As Microsoft's own C# documentation states:

For the arithmetic, casting, or conversion operation to throw an OverflowException, the operation must occur in a checked context. By default, arithmetic operations and overflows in Visual Basic are checked; in C#, they are not. If the operation occurs in an unchecked context, the result is truncated by discarding any high-order bits that do not fit into the destination type.

See the Remarks section on this page of the MSDN: https://msdn.microsoft.com/en-us/library/system.overflowexception(v=vs.110).aspx

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Filipe Strazzeri

Filipe Strazzeri

How would you go about catching the overflow exception Jeremy talks about in the end of the video ?

2 Answers

andren

andren

Filipe Strazzeri

Filipe Strazzeri

Damian Adams

Damian Adams