How do I test a try-catch?

Question

I was trying out some code in my catch method, and I wanted to try out the exception that it generates. but in order to reach the catch method, I need to crash my program, so it'll be caught and create an exception.

try
{
    //do something
}
catch (Exception ex)
{
    MessageBox.Show("There was an error, please contact the staff");
    using (StreamWriter writer = new StreamWriter(Application.StartupPath + "\\Crashlog\\Crashfile.txt"))
    {
        writer.WriteLine(ex.ToString());
    }
}

Now I wonder, what's an easy, and simple to memorise, line of code that surely makes your program reach that catch method and generate an exception?

What if `StreamWriter` fails to create/write `Crashfile.txt` file? E.g. if the routine starts from `C:\Program Files\MyRoutine` (usual path to start from) Windows doesn't allow you to create file here (unless you're an admin) — Dmitry Bychenko, Dec 14 '16 at 14:35
Do not forget to write down as many data as you can: *Message*, *Stack trace*, *Exception type* — Dmitry Bychenko, Dec 14 '16 at 14:36
Think on *dependency injection* - what if you'll want, say, to send a eMail with exception data — Dmitry Bychenko, Dec 14 '16 at 14:51

score 10 · Accepted Answer · edited Dec 14 '16 at 14:32

10

try
{
    throw new Exception();
}

edited Dec 14 '16 at 14:32

Bathsheba

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answered Dec 14 '16 at 14:31

Magnus

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Bathsheba · Answer 2 · 2016-12-14T14:39:14.137

6

throw new Exception("Test"); is a reliable way.

You could even include something more useful than "Test".

edited Dec 14 '16 at 14:39

answered Dec 14 '16 at 14:31

Bathsheba

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What would the "Test" string do if I'll use that? – Steven Dec 14 '16 at 14:54
1

You'd be able to inspect the contents of the exception at the `catch` site. – Bathsheba Dec 14 '16 at 14:58

score 3 · Answer 3 · edited Dec 14 '16 at 14:47

3

one of the things I like to use in such cases is this:

int div = 0;

int res = 3/div;

this will throw a DivideByZeroException

Usually this is something that should not be applied, especially if you are programming on PLC level. But in the C# world it is just an easy mosquito sting.

edited Dec 14 '16 at 14:47

Bathsheba

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answered Dec 14 '16 at 14:31

Mong Zhu

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I dislike this with a vengeance. Coming from a C and C++ world, this is undefined behaviour. There are better alternatives. – Bathsheba Dec 14 '16 at 14:32
@Bathsheba that is true ;) – Mong Zhu Dec 14 '16 at 14:33
1

But I don't think this is incorrect from a C# perspective. Have an upvote! – Bathsheba Dec 14 '16 at 14:33

How do I test a try-catch?

3 Answers3