How do I limit the WPF TextBox to a numerical value between 1-50-CodePudding

So I have a TextBox and I want to limit the input to a numerical value from 0 - 50, is this possible? I've looked at some Regex examples using the PreviewTextInput but that only validates one number at a time.

I've also tried utilizing the MaxLength property, but that didn't seem to do much.

CodePudding user response：

Using WPFToolkit you can use IntegerUpDown (it's an easy way)

If not Should be like this (using preview text input)

<TextBox Name="NumberTextBoxLimited" PreviewTextInput="NumberValidationTextBox"/>

And using regular expressions

using System.Text.RegularExpressions;
private void NumberValidationTextBox(object sender, TextCompositionEventArgs e)
{
    e.Handled = new Regex(@"^(0?\d|[1-4]\d|50)$").IsMatch(e.Text);
}

CodePudding user response：

Consider treating this as a validation issue.

For instance, you could create a rule that inherits from ValidationRule that contains your custom validation logic.

public class NumberValidationRule : ValidationRule
{
  public override ValidationResult Validate(object value, CultureInfo cultureInfo)
  {
    int number;
    if (!int.TryParse(value.ToString(), out number))
    {
      return new ValidationResult(false, "Not a number");
    }
    
    if (number < 0 || number > 50) 
    {
      return new ValidationResult(false, "Not between 0 and 50.");
    }

    return new ValidationResult(true, null);
}

Then in your binding you'd add a the rule (like the snippet below for your TextBox). I omitted some extraneous Xaml for brevity.

<TextBox.Text>
  <Binding ...>
    <Binding.ValidationRules>
      <local:NumberValidationRule ValidationStep="RawProposedValue" />
    </Binding.ValidationRules>
  </Binding>
</TextBox.Text>

Another way would be to implement IDataErrorInfo on the model and put the validation logic there. You'd have to change the UpdateSourceTrigger to include ValidatesOnDataError=True as well.