WPF: simple TextBox data binding

Question

I have this class:

public partial class Window1 : Window
{
    public String Name2;

    public Window1()
    {
        InitializeComponent();
        Name2 = new String('a', 5);
        myGrid.DataContext = this;
    }

    // ...
}

And I want to display the string Name2 in the textbox.

<Grid Name="myGrid" Height="437.274">
  <TextBox Text="{Binding Path=Name2}"/>
</Grid>

But the string isn't displayed. Also, if the string Name2 is updated periodically using a TimerCallback, do I need to do anything to make sure the textbox is updated when the data changes?

As a tip, you can format code by indenting by four spaces or using the 101010 button -- saves manually mucking around with br tags and escaping angle brackets! — itowlson, Nov 12 '09 at 21:39

score 91 · Accepted Answer · edited Oct 22 '18 at 01:04

Name2 is a field. WPF binds only to properties. Change it to:

public string Name2 { get; set; }

Be warned that with this minimal implementation, your TextBox won't respond to programmatic changes to Name2. So for your timer update scenario, you'll need to implement INotifyPropertyChanged:

partial class Window1 : Window, INotifyPropertyChanged
{
  public event PropertyChangedEventHandler PropertyChanged;

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

  private string _name2;

  public string Name2
  {
    get { return _name2; }
    set
    {
      if (value != _name2)
      {
         _name2 = value;
         OnPropertyChanged("Name2");
      }
    }
  }
}

You should consider moving this to a separate data object rather than on your Window class.

Example from MSDN on implementing the INotifyPropertyChanged interface (scroll down to DemoCustomer implementation): http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged(v=vs.110).aspx — Juha Palomäki, Nov 27 '13 at 20:16

score 10 · Answer 2 · answered Jun 11 '15 at 16:41

10

Just for future needs.

In Visual Studio 2013 with .NET Framework 4.5, for a window property, try adding ElementName=window to make it work.

<Grid Name="myGrid" Height="437.274">
  <TextBox Text="{Binding Path=Name2, ElementName=window}"/>
</Grid>

answered Jun 11 '15 at 16:41

Stefan Cantacuz

131
1
3

1

On XAML side, once Name2 has been included in the INotifyPropertyChanged interface. – Wayne Lo Jul 05 '21 at 02:37

score 9 · Answer 3 · answered Nov 12 '09 at 21:44

Your Window is not implementing the necessary data binding notifications that the grid requires to use it as a data source, namely the INotifyPropertyChanged interface.

Your "Name2" string needs also to be a property and not a public variable, as data binding is for use with properties.

Implementing the necessary interfaces for using an object as a data source can be found here.

WPF: simple TextBox data binding

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