How Can I Restrict Input in a WPF TextBox to Only Numeric Values and a Decimal Point?

Restricting WPF TextBox Input to Numeric Values and a Decimal Point

Need a WPF TextBox that accepts only numbers and a decimal point, without allowing any signs? While a NumericUpDown control might seem like a solution, it may not fit your application's design. A more flexible approach uses the PreviewTextInput and DataObject.Pasting events.

Add the PreviewTextInput event to your TextBox definition like this: <TextBox PreviewTextInput="PreviewTextInput"></TextBox>.

The PreviewTextInput event handler checks if the input is valid using a regular expression. This example allows only digits, periods (.), and hyphens (-):

<code class="language-csharp">private static readonly Regex _regex = new Regex("[^0-9.-]+"); // Regex for disallowed characters

private static bool IsTextAllowed(string text)
{
    return !_regex.IsMatch(text);
}

private void PreviewTextInput(object sender, TextCompositionEventArgs e)
{
    e.Handled = !IsTextAllowed(e.Text);
}</code>

To prevent pasting invalid data, handle the DataObject.Pasting event:

<code class="language-csharp">private void TextBoxPasting(object sender, DataObjectPastingEventArgs e)
{
    if (e.DataObject.GetDataPresent(typeof(String)))
    {
        string text = (string)e.DataObject.GetData(typeof(String));
        if (!IsTextAllowed(text))
        {
            e.CancelCommand();
        }
    }
    else
    {
        e.CancelCommand();
    }
}</code>

These methods ensure your TextBox accepts only numeric input, providing a clean and efficient solution tailored to your application's design.

The above is the detailed content of How Can I Restrict Input in a WPF TextBox to Only Numeric Values and a Decimal Point?. For more information, please follow other related articles on the PHP Chinese website!