Key press event in WPF

Question

3.25/5 (4 votes)

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Hi..
I want user to enter only numeric values in textbox.
I got this code:

C#

private void txtType1_KeyPress(object sender, KeyPressEventArgs e)
{
     int isNumber = 0;
     e.Handled = !int.TryParse(e.KeyChar.ToString(), out isNumber);
}

but i am not getting textbox_KeyPress event.

Whats the solution?

Posted 17-May-10 20:16pm

niravsahayata

Updated 17-May-10 20:39pm

Abhinav S

v2

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Comments

Akinmade Bond 2-Nov-12 12:56pm

You should use the KeyDown or PreviewKeyDown event. Plus, the code you got is not for WPF, it's for WinForm.

Nelek 2-Nov-12 13:04pm

Have you noticed that the question is from 2010?

Akinmade Bond 3-Nov-12 8:56am

Oops. Hadn't noticed. :O

4 solutions

Solution 1

Validations in WPF should be handled using validation rules.
Have a look at this article.

Posted 17-May-10 20:38pm

Abhinav S

Comments

Clifford Nelson 2-Nov-12 18:48pm

That is not necessarily true since cannot deal with context issues with this technology. It works for simple validation, but not validation against other values. Not my vote of 1.

louie_nz 7-Nov-14 18:47pm

Maybe it's out of date, but responsibly speaking, so far WPF vaidation rules should be the better solution.

Solution 3

KeyPress in winforms was just perfect for input parsing,
unfortunately WPF don't have such event ;(
here my metod for parsing textbox input, allowing to input signed decimal number
(code is sucks but i cant find simpler way)

C#

private void textBox1_PreviewTextInput(object sender, TextCompositionEventArgs e)
        {
            if (!char.IsNumber(e.Text, e.Text.Length-1))
            {
                e.Handled = true;
            }

            if (( (e.Text).ToCharArray()[e.Text.Length - 1] == '.') || ((e.Text).ToCharArray()[e.Text.Length - 1] == ',')) 
            {
                e.Handled = true;
                if (!(((TextBox)sender).Text.Contains('.')))
                {
                    if (((TextBox)sender).Text.Length == 0) { ((TextBox)sender).Text = "0."; ((TextBox)sender).CaretIndex = ((TextBox)sender).Text.Length; }
                    else { ((TextBox)sender).Text += "."; ((TextBox)sender).CaretIndex = ((TextBox)sender).Text.Length; }
                }
            }
            if ((e.Text).ToCharArray()[e.Text.Length - 1] == '-' & !((TextBox)sender).Text.Contains('-')) { e.Handled = true; ((TextBox)sender).Text = "-" + ((TextBox)sender).Text; ((TextBox)sender).CaretIndex = ((TextBox)sender).Text.Length; }
            if ((e.Text).ToCharArray()[e.Text.Length - 1] == '+' & ((TextBox)sender).Text.Contains('-')) { e.Handled = true; ((TextBox)sender).Text=((TextBox)sender).Text.Substring(1); ((TextBox)sender).CaretIndex = ((TextBox)sender).Text.Length; }
 }

Posted 29-Sep-11 20:14pm

BlackBanzai

Updated 29-Sep-11 20:16pm

v2

Comments

Akinmade Bond 2-Nov-12 12:51pm

There is a simpler way, look at my answer.

Bijay Kant Salotry 13-Nov-13 8:14am

Thank you...your solution works for me.

Clifford Nelson 2-Nov-12 18:56pm

Using the PreviewTextInput is not a good idea. KeyDown event works just fine. Also, much too complex for what was asked for. Don't have to worry about signs, or decimal points.

CQüeb 27-Jun-13 18:57pm

Thank you for this awesome code.. really useful. If someone don't need manage the signs or decimal points.. that adapt the code for his requirements.. we are developers... :)

Hrvoje Batrnek 9-Mar-19 4:53am

This does not handle space.

Solution 2

Hello,
Try my code its simple

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
//allows only number
            if (char.IsNumber(e.KeyChar) == false)
            {
                e.Handled = true;
            }
//backspace working code
            if (e.KeyChar == (char)Keys.Back)
            {
                e.Handled = false;
            }
        }

Do rate my answer once you find it useful
Thanks & Regards
Radix :rose:

Posted 18-May-10 16:59pm

radix3

Comments

Souvik Banerjee 21-Jun-10 1:10am

Reason for my vote of 1
@Radix: Your code looks like a code for .NET 2.0. In KeyPressEventArgs in WPF, there is no e.KeyChar.

Akinmade Bond 2-Nov-12 11:50am

Your code would only work in WinForms, sorry.

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Akinmade Bond · Accepted Answer · 2012-11-02T06:52:00

Solution 4

Try this.

C#

private void NumericTextBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
    if (!Char.IsDigit((char)KeyInterop.VirtualKeyFromKey(e.Key)) & e.Key != Key.Back | e.Key == Key.Space)
    {
        e.Handled = true;
        MessageBox.Show("I only accept numbers, sorry. :(", "This textbox says...");
    }
}

You may need to import System.Windows.Input to get KeyInterop

The code segment above goes into the PreviewKeyDown event of the TextBox.

Posted 2-Nov-12 6:52am

Akinmade Bond

Comments

Parteek1991 17-Nov-12 5:53am

Thankyou Sir...

Akinmade Bond 17-Nov-12 7:43am

Happy to help. :)

CQüeb 27-Jun-13 18:52pm

This approach seems good, but allows capture the shift key, causing that characters !"#$%&/()=?¡ becomes to be captured.

anjulanka 11-Jan-15 20:36pm

This doesn't support NumPad keys

Member 13935090 10-Oct-18 5:26am

This doesn't work with NumPad Digits