Question

I hope someone can help me with this one, I suspect I am doing something stupid. I have bound a TextBox so that the Text is bound to InputValue. Basically, when the text value changes I have a method (Inches.Parse), which examines the value and returns a well formatted string.

If there are no errors with the parsing I want the textbox to have the well formatted string called “result”. However, the TextBox won’t show the new text? Any help would be appreciated.

public string InputValue 
{
    get
    {
        return _inputValue;
    }
    set
    {
        if (_inputValue != value)
        {                                        
            bool error;
            string result = Inches.Parse(value, 64, out error);                    

            if (error != IsValid)
            {
                IsValid = error;
            }
            if (!error)
            {
                _inputValue = result;
            }
            else
            {
                _inputValue = value;
            }

            NotifyPropertyChanged("InputValue");
        }
    }
}

Answer 1

This is a bug/issue that will apparently be fixed in dot net 4.0

Basically the problem is that if a binding sets a property it does not look for NotifyPropertyChanged during the setter. you can workaround this issue, by calling NotifyPropertyChanged on the main ui thread with a dispatcher. it is done like this

Application.Current.Dispatcher.BeginInvoke((Action)delegate { NotifyPropertyChanged("InputValue"); });

put this in your setter and you should be fine..