Format Exception, What Am I Doing Wrong?

Question

4.00/5 (1 vote)

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I want that my app, when someone enters a letter, or sometehing that isn't a number, shows this message: "You must enter a number!"

C#

void Button_guessClick(object sender, EventArgs e)
{
    try
    {
        int guess = Convert.ToInt32(textBox_guess.Text);
    }
    catch(FormatException ex)
    {
    	MessageBox.Show("You must enter a number!");
    }

    if (guess > number)
    {
    	MessageBox.Show("The number is smaller!");
    }
    
    if (guess < number)
    {
    	MessageBox.Show("The number is bigger!");
    }
    
    if (guess == number)
    {
    	MessageBox.Show("Bravo, you have guessed it");
    	Application.Exit();
    }
}

Posted 7-Jun-14 23:06pm

Member 10871142

Updated 7-Jun-14 23:42pm

Kornfeld Eliyahu Peter

v3

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Kornfeld Eliyahu Peter · Answer 1 · 2014-06-07T23:26:00

Solution 1

It's not exactly clear to me what went wrong with you, but I think that the base of your approach is wrong...
You should not use try...catch - it's a very expensive writing...
Do use Int32.TryParse[^] to check if the value is numeric...

Posted 7-Jun-14 23:26pm

Kornfeld Eliyahu Peter

Comments

OriginalGriff 8-Jun-14 6:30am

Thank you!
But you missed the typo... :laugh:

Kornfeld Eliyahu Peter 8-Jun-14 6:56am

I'm full of typo myself - can't get care of yours too...

OriginalGriff 8-Jun-14 6:58am

Damn!
There was me hoping I'd got myself a spell check wallah! :laugh:

Kornfeld Eliyahu Peter 8-Jun-14 6:58am

OT - a few weeks now I do not get notifications on such comments like yours here. Did you encountered such a problem (it makes me hard to follow Q&A)...
(Reported on Bugs - twice I think)

OriginalGriff 8-Jun-14 7:00am

Yes - Same thing, and I've reported it as well.
There do seem to be quite a few fairly serious bugs creeping in here: I think the hamsters have been paying too much attention to Workspaces and not enough to what they are doing with maintenance...

Kornfeld Eliyahu Peter 8-Jun-14 7:01am

I think hamsters gone for a vacation!

OriginalGriff · Answer 2 · 2014-06-07T23:27:00

Why not do it properly, instead of using exceptiosn as part of your "normal operation" processing?

C#

int guess;

if (!int.TryParse(textbox_guess.Text, out guess))
   {
   MessageBox.Show("You must enter a number!");
   }
else
   {
   if (guess > number...

[edit]Indentation reverted - OriginalGriff[/edit]

DamithSL · Answer 3 · 2014-06-07T23:32:00

Solution 3

problem is after you get exception you are not exist the function. then other validations will perform and you will get some other messages as well.

C#

try{
int guess = Convert.ToInt32(textBox_guess.Text);
}

catch(FormatException ex){
    MessageBox.Show("You must enter a number!");
    return; // this will return from your function no more messages will show..
}

you better use Int32.TryParse as Other answers pointed out.

Posted 7-Jun-14 23:32pm

DamithSL

Comments

OriginalGriff 8-Jun-14 5:38am

Did I ask you to re-indent my code for me?
No.

So leave it alone. It may not be your preferred style, but that does not mean you should impose yours on others.

DamithSL 8-Jun-14 6:01am

:) never do it again, by the way, you have code line out side of the coding block. I don't need to comment and say this minor mistake to highest reputation holding person here in CP. That's why I have edited. Sorry if I did something wrong

DamithSL 8-Jun-14 6:54am

Now some one else edit the same post, you say Thanks :-)

OriginalGriff 8-Jun-14 6:57am

Yes.
Because his change was sensible, yours was gratuitous! :laugh:

DamithSL 8-Jun-14 7:11am

lesson learned

Kornfeld Eliyahu Peter 8-Jun-14 7:03am

Do not take it too hard - The fact that OG drank his coffee in between the two edits...I just got luck to edit it AFTER!!!

DamithSL 8-Jun-14 7:12am

np :)

Abhinav S · Answer 4 · 2014-06-07T23:38:00

Solution 4

Convert.ToInt does not check if an input is really an integer or not.
To check type, use a Int.TryParse.

To be cautious about cultures, go through Check If A String Value Is Numeric[^].

Posted 7-Jun-14 23:38pm

Abhinav S