Only allow digits in textbox C#

Question

Possible Duplicate:
How can I allow only 0 or 1 to be entered in a TextBox?
Allow only integers in TextBoxes

I'm working on a program now and I have a few simple textboxes. I keep getting an error when the input of the textbox is NOT a number, because it tries to convert it to a integer.

The code is very basic:

    int optelNumber = Convert.ToInt32(textBox2.Text);
    MessageBox.Show("Please enter a digit."); //if optelNumber is not a digit

for example:

input in textbox = "Hello !" => pops up the Mess.Box
input in textbox = 123245 => keep running the program

Hope this is enough information. I've searched almost all other topics but all the code was to advanced for me. :( Thanks for your time

edit :

The messagebox is to catch the error and keep the program from crashing.

edit :

int vedett = 0, duvel = 0, kDuvel = 0, kriek = 0, pils = 0;

//only digits allowed here
int optelNumber = Convert.ToInt32(textBox2.Text);

switch(comboItem)
{
case "vedett":
  vedett += optelNumber;
  break;
case "duvel":
  duvel += optelNumber;
  break;
case "kl. duvel":
  kDuvel += optelNumber;
  break;
case "pils":
  pils += optelNumber;
  break;
case "kriek":
  kriek += optelNumber;
  break;
case "":
  MessageBox.Show("Kies een andere drank.");
  break;
}

I don't know if this is want you need, but may help http://blog.csharphelper.com/2012/11/20/throw-standard-exceptions-in-c.aspx — Cesar A. Rivas, Feb 04 '13 at 23:14

score 3 · Answer 1 · answered Feb 04 '13 at 23:13

3

You need to do a int.TryPase

    int result;
    if (int.TryParse(textBox2.Text, out result))
      int optelNumber = Convert.ToInt32(textBox2.Text);

or

int result;
int optelNumber; 
        if (int.TryParse(textBox2.Text, out result))
          optelNumber  = result;

answered Feb 04 '13 at 23:13

DJ Burb

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3

What's the reason for using `Convert.ToInt32` again? result has the value..? – Lews Therin Feb 04 '13 at 23:15
`ConvertToInt32` calls `int.Parse` implicitely. But if the string is null `int.Parse` throws an exception whereas `Convert.ToInt32` returns 0. – Tim Schmelter Feb 04 '13 at 23:18
edited for better coding practices. Either one should work though – DJ Burb Feb 04 '13 at 23:19
Doesn't really work no :s its probably me, ill add the rest of the code to make it mroe clearly – Nick Peelman Feb 04 '13 at 23:21
@DJBurb I've just never seen it used that way.. – Lews Therin Feb 04 '13 at 23:22
DjBurb, It worked for me, I just had to figure out what if (int.TryParse(textBox2.Text, out result)) Did. Thanks so much ! – Nick Peelman Feb 04 '13 at 23:37
@LewsTherin: Why did you remove your answer? – Patrick Feb 04 '13 at 23:39
@Patrick Hey, I dunno.. DjBurb has it right :P Although, I still don't see the point of the 1st method :O – Lews Therin Feb 04 '13 at 23:48
@LewsTherin: But your answer was cleaner. I don't get the first method in this answer either. I don't see the "better coding practices" either. – Patrick Feb 04 '13 at 23:52
@Patrick Lol, neither do I. I will do some reading later to see if I did miss anything.. either way it seems the OP has it figured out though ;) – Lews Therin Feb 04 '13 at 23:56
Nick, if this answer helped can you accept it? – DJ Burb Feb 14 '13 at 19:56

Only allow digits in textbox C#

1 Answers1