TextBox.Text绑定到ViewModel的属性

Question

I have a problem with two way binding a TextBox content to a property in another class. Searching stackoverflow gave a lot of tips/solutions but none seem to work.

In my XAML code I have:

< TextBox ... Width="336" IsReadOnly="True"
 Text="{Binding Path=AssignedClearProgram, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>

(... I removed all non important items)

In the accompanies cs code I have:

public CombiWindow(Combi combi)
{
    ViewModel = new CombiViewModel(combi);
    DataContext = ViewModel;
}

In the CombiViewModel:

    [UsedImplicitly]
    public string AssignedClearProgram { get; set; }

It seems that the first time I assign AssignedClearProgram, the textbox is filled with the text that I set, however after the window is displayed and AssignedClearProgram gets updated from the code (ie the set method is called), the data is not updated in the screen.

Does anybody have a solution to update the textbox when this variable is changed?

Kind regards,

Michel

Answer 1

Your viewmodel class needs to implement INotifyPropertyChanged and you need to raise that interface's event whenever you change the property. Then the binding will spot changes and update the textbox.

Answer 2

Your view model class should implement the INotifyPropertyChanged interface.

Your property would then look like the following:

private string assignedClearProgram;

public string AssignedClearProgram
{
   get { return assignedClearProgram; }
   set
   {
       if (assignedClearProgram != value)
       {
           assignedClearProgram = value;

           // Notify property has changed here using PropertyChanged event from INotifyPropertyChanged.
       }
   }
}

Read this article for an example of how to implement the INotifyPropertyChanged interface and utilize its PropertyChanged event.