Only allow for a double in textbox

tonyonlinux

I have looked on google and I can't find anything that does what I need in an example.. I want to validate the textbox on keypress and make it where the user(me) can't enter anything other than a price value. like 1.99 2.99 whatever.. I have it working so far as to only allow numbers a backspace and the '.' but I can't figure out how to restrict it to only 2 places after the decimal. Any help would be great. thanks.. Here is what I have so far...

private void Price_KeyPress(object sender, KeyPressEventArgs e)
{

        e.Handled = !Char.IsNumber(e.KeyChar) && (e.KeyChar != '\\b')&& (e.KeyChar != '.');

        
    }

Jimmanuel

Use a NumericUpDown instead. It accepts only numeric input and you can specify in the designer how many decimal places it should use - no custom coding necessary.

:badger:

Dan Mos

as Jimmanuel said you could use the numeric... But I have found some small bugs in the numeric up down such: as you introduce some number then delete it and if you get the .Value it's not null or zero or... So, I had this problem too. Sorry I can find the code right now nor the time to write it but this is how you could do it: use the KeyDown event and then put the logic:

//check if it already contains a dot '.' character by using the text property
//if it does then allow only number and refuse everything else using
e.Handled=true;
e.SuppressKeyPress=true;
//also check the number of chars after the '.' sign

//else allow dot and numbers.

use

e.KeyCode == Keys.OemPeriod

to check for '.' hope it helps

Luc Pattyn

Not quite, you can enter more decimals, its only when you Leave the Control that it gets rounded to the specified number of decimals. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.
[The QA section does it automatically now, I hope we soon get it on regular forums as well]

Luc Pattyn

just checking the latest keystroke as if it comes at the right of what is already there isn't sufficient: 1. the caret might not be at the end 2. you may want to support: copy, cut, paste, backspace... all of these require more than just checking the new character. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.
[The QA section does it automatically now, I hope we soon get it on regular forums as well]

Dan Mos

true. but I checked for stuff like that(if it's the delete key, back key etc) As for the position of the caret/cursor I didn't really cared cause I transformed .8686 in 0.8686 It really works for me. What I said here/before are some "guide lines". Again sorry I can't find the code. Just the *.dll. Thanks for the correction. I mean it. It should help TonyOnLinux too if he decides to implement he's own logic/control.

DaveyM69

A while ago I wrote this article[^] for a simple numeric text box. It would need some alteration to allow a decimal point and to check the number is valid for your requirements (at the moment it only allows numeric input i.e. it is still a text box and not a NumberBox) but it could serve as a starting point. It handles copy and paste via keyboard/mouse and all edit keys etc...

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Why are you using VB6? Do you hate yourself? (Christian Graus)

OkkiePepernoot

Why not using a ConvertEventHandler delegate ?

hasarian

You need only to check the text of textbox. My textbox is name tAmount

private void tAmount_KeyPress(object sender, KeyPressEventArgs e)
{
int isNumber = 0;
Update();
string tmp = Convert.ToString(tAmount.Text);
if (tmp.Contains(".") == true)
e.Handled = !int.TryParse(e.KeyChar.ToString(), out isNumber) && (e.KeyChar != '\b');
else
e.Handled = !int.TryParse(e.KeyChar.ToString(), out isNumber) && (e.KeyChar != '\b') && (e.KeyChar != '.');