Use SelectionChanged event in two textbox , one depend from the other

Question

I have two Textbox and I'm trying to add SelectionChanged Event to the two textbox :

TextBox A => Amount
TextBox B => Summary

The scenario is like :

Two Textbox are empty:

• The user enter the amount the summary will be equals to 100 * Amount

• The user enter the summary after clear the field of amount , he should get summary / 100 in the textbox of amount

   private void Amount_SelectionChanged(object sender, RoutedEventArgs e)
    {
        if (!string.IsNullOrEmpty(Amount.Text.ToString()))
        {
            Summary.IsReadOnly = true;
            Summary.Text = (ToDecimalValue(Amount.Text) * 100).ToString();
            Amount.IsReadOnly = false;
  
        }
        else
        {
            Summary.Text = "";
            Summary.IsReadOnly = false;
        }
  
  
    }
  
    private void Summary_SelectionChanged(object sender, RoutedEventArgs e)
    {
        if (!string.IsNullOrEmpty(Summary.Text.ToString()))
        {
            Amount.IsReadOnly = true;
            Amount.Text = (ToDecimalValue(Summary.Text) / 100).ToString()
            Summary.IsReadOnly = false;
  
        }
        else
        {
            Summary.Text = "";
            Summary.IsReadOnly = false;
        }
  
    }
  

How can I do this?

Answer 1

I believe there is a simple solution:

private bool _isEditing;

private void Amount_TextChanged(object _, RoutedEventArgs __)
{
    if (_isEditing)
        return;

    _isEditing = true;

    if (double.TryParse(Amount.Text, out double amount)
        Summary.Text = (amount * 100).ToString();
    else
        Summary.Clear();

    _isEditing = false;
}

private void Summary_TextChanged(object _, RoutedEventArgs __)
{
    if (_isEditing)
        return;

    _isEditing = true;

    if (double.TryParse(Summary.Text, out double summary)
        Amount.Text = (summary / 100).ToString();
    else
        Amount.Clear();

    _isEditing = false;
}

Notes:

• I changed "SelectionChanged" to "TextChanged", as it is the event you want to watch if the user changes the value in the TextBox.
• I replaced ToDecimalValue() by double.TryParse(), but this will work only if the decimal separator matches that of the application's current culture.
• _ and __ mean that the parameters are not used.
• If you want the TextBox to only accepts numbers, see this question.