set textbox text using wpf and Devexpress MVVM

Question

How can i set the Text of a Textbox using wpf and Devexpress free MVVM when a button is clicked?

This is the xaml code of my Textbox

<TextBox Width="200" Grid.Column="1" Text="{Binding SelectedText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" FontSize="14"/>

this is my VM code

        public virtual string SelectedText { get; set; }
        void AutoUpdateCommandExecute()
        {
            Console.WriteLine("Code is Executing");
            SelectedText = "TextBox Text is Not Changing";
        }

The code is Executing but it doesn't change the Text of the Textbox

But when i type something in the textbox and get the text of that textbox using this code.

        void AutoUpdateCommandExecute()
        {
            Console.WriteLine("Code is Executing");
            Console.WriteLine(SelectedText);
        }

It prints the Text i typed in the Textbox. So what did i do wrong? I can't set the Text?

Thank you.

Answer 1

your selected text needs to be either a DependencyProperty which will then notify the binding that it's value has changed...

public static readonly DependencyProperty SelectedTextProperty = DependencyProperty.Register("SelectedText", typeof(string), typeof(YourClassType));

public string SelectedText
{
  get { return (string)GetValue(SelectedTextProperty ); }
  set { SetValue(SelectedTextProperty , value); }
}

OR

your VM needs to implement INotifyPropertyChanged interface and in the SelectedText setter you need to fire a property changed event...

public class VM : INotifyPropertyChanged
{
  public event PropertyChangedEventHandler PropertyChanged;
  private string _selectedText;
  public string SelectedText
  {
    get { return _selectedText; }
    set
    {
      _selectedText = value;
      RaisePropertyChanged("SelectedText");
    }
  }

  private void RaisePropertyChanged(string propertyName)
  {
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
  }
}