Sometimes you only want to enter numeric data in a textbox.
You have two options here :
Let a user type whatever he/she wants into a textbox, validate the input and show him or her an annoying message that he/she has done something wrong.:angry:
Or: capture the key before input, check if it's "numeric" and allow only "numerics" to come through. That way, you know the input is correct and you can proceed.:)
A decimal point should be correct input, but only once.
The next snippet does this and is easily adapted to allow for sientific input(+,-,e,E)
Capturing numeric input in a TextBox
bool NumberEntered = false;
//Check if key entered is "numeric".
private bool CheckIfNumericKey(Keys K, bool isDecimalPoint)
{
if (K == Keys.Back) //backspace?
return true;
else if (K == Keys.OemPeriod || K == Keys.Decimal) //decimal point?
return isDecimalPoint ? false : true; //or: return !isDecimalPoint
else if ((K >= Keys.D0) && (K <= Keys.D9)) //digit from top of keyboard?
return true;
else if ((K >= Keys.NumPad0) && (K <= Keys.NumPad9)) //digit from keypad?
return true;
else
return false; //no "numeric" key
}
private void MyTextbox_KeyDown(object sender, KeyEventArgs e)
{
//Get our textbox.
TextBox Tbx = (TextBox)sender;
// Initialize the flag.
NumberEntered = CheckIfNumericKey(e.KeyCode, Tbx.Text.Contains("."));
}
// This event occurs after the KeyDown event and can be used to prevent
// characters from entering the control.
private void MyTextbox_KeyPress(object sender, KeyPressEventArgs e)
{
// Check for the flag being set in the KeyDown event.
if (NumberEntered == false)
{
// Stop the character from being entered into the control since it is non-numerical.
e.Handled = true;
}
}
ddanbe 2,724 Professional Procrastinator Featured Poster
Line 26 : // This event occurs...
This is of course not the event, this is the event handler method after the event occured.
arame 0 Newbie Poster
The best way to do this now is to use the Ajax FilteredTextBoxExtender control.
ddanbe 2,724 Professional Procrastinator Featured Poster
I thought AJAX to be Asynchronous JavaScript + XML or am I wrong?
Just disscussing a textbox in a plain simple forms application in C# here!
tontano 0 Newbie Poster
Just so everybody knows what environment I am using. It's C# and Windows Form using Visual Studio 2010.
skatamatic 371 Practically a Posting Shark
Wouldn't this allow the user to enter "....." as a number?
I wonder how efficient this would be:
private void MyTextbox_KeyPress(object sender, KeyPressEventArgs e)
{
int aDouble = 0;
// Check for the flag being set in the KeyDown event.
if (double.TryParse(MyTextBox.Text + e.KeyChar, out aDouble))
MyTextbox.Tag = aDouble;
else
// Stop the character from being entered into the control since it is non-numerical.
e.Handled = true;
}This has the added benefit of storing the numeric value of the textbox in the textbox's .Tag.
ddanbe commented: original approach! +15
ddanbe 2,724 Professional Procrastinator Featured Poster
@tontano The snippet is real C#, not something else. If you got questions about the code, please feel free to ask.
@skatamatic :
First : "...." question: no, on line 23 I use Tbx.Text.Contains(".")
Second your code:
Line 3 should read double aDouble = 0; I guess.
I could type 1.......
I could correctly type 1.5, but when I use the Tag.ToString() method and showed it in a MessageBox it gave 15
How about backspace?
Still your idea is well worth thinking of :-/
tontano 0 Newbie Poster
@ddanbe, @skatamatic - Thanks for your effort in helping me..
I do however have a stupid question (at least for me)...What about the use of errorProvider or something like that? Or what about using the events "Validating / Validated"...Again, I know this may sound like a stupid question, and I am sorry for asking....
Thanks guys
skatamatic 371 Practically a Posting Shark
Hah sorry for my broken code. I am away from my compiler. I also noticed that the code I posted won't handle negatives unless there's already a number there (since a - by itself is not a valid double, but a -5 is). Not sure about the object.tostring issue, that doesn't really make sense (there is nothing in that code to remove a period...)
ddanbe 2,724 Professional Procrastinator Featured Poster
@tontano: there are no stupid questions, only stupid answers.
THe whole point of my snippet is just to avoid things like ErrorProvider and Validating!
@skatamatic: You found a flaw in my code! I don't do negatives!Aaargh:@ But then again, I don't do copy and paste either. Maybe I should implement them if I find the time...
Morgan_2 0 Newbie Poster
Massive bump I know, apolagies.
I've found your code very useful thanks ddanbe, buuut I was wondering if there is a way to allow a decimal point to be input before anything else in the textbox? Currently it crashes the solution :S I've tried editing the current code but to no avail (I'm very new to this).
Any help would be much appreciated!
noface0711 0 Newbie Poster
The best way to do this now is to use the Ajax FilteredTextBoxExtender control.
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