DataBinding to a TextBox not working

Question

I am having a difficult time getting my WPF to properly use Databinding. In the XAML I have a the following:

....
<TextBox Name="txt_FirstName" Text="{Binding Path=currentApplication.FirstName, UpdateSourceTrigger=PropertyChanged}" />
....

I have in the following CS code:

namespace WPF1
{
  public partial class MainWindow : Window
  {
    personalApp currentApplication = new personalApp ();

    public MainWindow()
    {
      InitializeComponent();
    }

  }
}

That references the following two classes:

class personalApp : INotifyPropertyChanged
{
  private Person person = new Person();

  public string FirstName
  {
    get { return person.FirstName; }
    set
    {
      person.FirstName = value;
      this.OnPropertyChanged("FirstName");
    }
  }

  public event PropertyChangedEventHandler PropertyChanged;

  void OnPropertyChanged(string propName)
  {
    if (this.PropertyChanged != null)
      this.PropertyChanged(
      this, new PropertyChangedEventArgs(propName));
   }

}

class Person
{
  private string firstName = "";

  get { return firstName; }
  set { FirstName = value; }
}

I pause it in the code and step through to check, but when I update the txt_FirstName in the application, it never seems to set the firstName Object.

Where am I going wrong?

Answer 1

You need to update your XAML binding, and set the DataContext of the Window using the TextBox .

namespace WPF1
{
  public partial class MainWindow : Window
  {
    personalApp currentApplication = new personalApp ();

    public MainWindow()
    {
      InitializeComponent();
      this.DataContext = currentApplication;
    }
  }
}

Updating the XAML:

<TextBox Name="txt_FirstName" Text="{Binding FirstName, UpdateSourceTrigger=PropertyChanged}" />

Answer 2

I have corrected the code.

For text box:

<TextBox Name="txt_FirstName" Height="30" Background="Beige"
             Text="{Binding Path=FirstName, UpdateSourceTrigger=PropertyChanged}" />

C# Code

namespace Wpf1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = new personalApp();
    }
}

internal class personalApp : INotifyPropertyChanged
{
    private Person person = new Person();

    public string FirstName
    {
        get { return person.FirstName; }
        set
        {
            person.FirstName = value;
            this.OnPropertyChanged("FirstName");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propName)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(
            this, new PropertyChangedEventArgs(propName));
    }
}

internal class Person
{
    public string FirstName { get; set; }
}
}

Answer 3

public MainWindow()
{
  DataContext = this;
  InitializeComponent();
}

or if you don't want to assign data context to yourself (window), as you might have other datacontext coming into the window, you can add this in xaml: give your window a name:

<Window .... x:Name="this"...

then

<TextBox Name="txt_FirstName" Text="{Binding ElementName=this,
                                     Path=currentApplication.FirstName/>

Answer 4

What you mean by "update the txt_FirstName in the application" ?
If you set directly the value of the textbox then you should try to set the value of currentApplication instead of the textbox value