Restricting textbox input to numbers in C# [closed]

Answer 1

Have a look at the below code

private void txtbox1_KeyPress(object sender, KeyPressEventArgs e)
    {
        const char Delete = (char)8;
        e.Handled = !Char.IsDigit(e.KeyChar) && e.KeyChar != Delete;
    }

This will be helpful but users can Copy and Paste characters :-)

Answer 2

From others have said before me, we have to almost know what you will use this in, WinForms, ASP.NET, Silverlight ...

But now I take a chance that it is WinForm:)

private void TxtBox1_KeyPress(object sender, KeyPressEventArgs e)
{
     if (!System.Text.RegularExpressions.Regex.IsMatch(e.KeyChar.ToString(), "\\d+"))
          e.Handled = true;
}

Answer 3

Not sure if this is the correct way, but it works for me, running it on the TextChanged event TextBox has:

    private void CoordinateValidation(object sender, TextChangedEventArgs e) {
        TextBox inputBox = e.OriginalSource as TextBox;
        inputBox.TextChanged -= CoordinateValidation;
        int caretPos = inputBox.CaretIndex;
        foreach (TextChange change in e.Changes) {
            if (inputBox.Text.Substring(change.Offset, change.AddedLength).Any(c => !ValidChars.Contains(c)) ||
                inputBox.Text.Count(c => c == '.') > 1 ||
                (inputBox.Text.Length > 0 && inputBox.Text.Substring(1).Contains('-'))) {
                inputBox.Text = inputBox.Text.Remove(change.Offset, change.AddedLength);
                caretPos -= change.AddedLength;
            }
        }
        inputBox.CaretIndex = caretPos;
        inputBox.TextChanged += CoordinateValidation;
    }

Answer 4

This may not be the best way, but works ok for WPF TextBox...

    private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
    {
        string originalText = ((TextBox)sender).Text.Trim();
        if (originalText.Length>0)
        {
            int inputOffset = e.Changes.ElementAt(0).Offset;
            char inputChar = originalText.ElementAt(inputOffset);
            if (!char.IsDigit(inputChar))
            {
                ((TextBox)sender).Text = originalText.Remove(inputOffset, 1);
            }
        }
    }