How can I limit the TextBox control to only allow the values 0 and 1?
Thanks. And I have one more question: How can I disable put text from clipboard in my textbox control?
+10
A:
By using the event KeyPress
private void NumericOnlyKeyBox_KeyPress(object sender, KeyPressEventArgs e)
{
var validKeys = new[] { Keys.Back, Keys.D0, Keys.D1 };
e.Handled = !validKeys.Contains((Keys)e.KeyChar);
}
Setting e.Handled to true / false indicates if the character should be accepted to the box or not.
You can read more about KeyPressEventArgs on MSDN.
Note
Keys.Delete should cover Keys.Delete, Keys.Backspace and other "Back" buttons.
Filip Ekberg
2010-05-21 13:24:31
Better this: `e.Handled = (e.KeyChar == Keys.D0) || (e.KeyChar == Keys.D1);`
abatishchev
2010-05-21 13:29:32
+1 -- Thanks. I didn't know that. :-)
Pretzel
2010-05-21 13:29:43
@abatishchev -- haha, clever. :-D
Pretzel
2010-05-21 13:30:25
@abatischev, Don't forget the numpad. :)
Filip Ekberg
2010-05-21 13:30:27
thank you for you answer!
Alexry
2010-05-21 13:32:49
You should also take care of backspace and delete
PoweRoy
2010-05-21 13:35:10
@PoweRoy, true, you need to accept those keys aswell.
Filip Ekberg
2010-05-21 13:35:30
Almost downvoted for using if-statement to set a boolean.
SergioL
2010-05-21 13:41:22
arrow keys? tab? what if they want to paste using Ctrl+V?
adam0101
2010-05-21 13:48:35
@adam0101: Try before ask ;) `KeyPress` will not be fired on pressing delete, arrows or tab. Yes, Ctrl+C/Ctrl+V will bot work but Cntrl+Ins/Shift+Ins will.
abatishchev
2010-05-21 14:02:20
@adam0101, refactored a bit. You can now use Delete key, Backspace, 0 , 1 numpad 0 and 1.
Filip Ekberg
2010-05-21 14:07:35
Right-click the text box and select Paste.
Hans Passant
2010-05-21 14:16:42
@Hans, Actually one solution would be to use `protected override void WndProc(ref Message m)` and check for paste/copy messages. But then you would have to override the TextBox and do that. Another solution is to override the TextChanged event and just add a loop that checks each character and removes the incorrect ones. To make the example a bit simple, I wont add that though, there's enough information in this last comment. :)
Filip Ekberg
2010-05-21 14:44:53
+2
A:
If you do want to show the numbers rather than a check or something but only want to allow 0 or 1 you could use a NumericUpDown control and set min to 0 max to 1 and step to 1.
If you do actually need a textbox I'd use Filip's answer but I'd set the MaxLength of it to 1 to avoid having to worry about 00, 11 or 01 or similar values.
ho1
2010-05-21 13:29:54
+1 -- I personally think that this is the best answer, really. And if you want it as a string, well then use .ToString() -- And you're done. (and so little code, too!)
Pretzel
2010-05-21 13:38:48