Data Binding between two TextBoxes in different windows

Question

I have created a program that changes the name in a TextBox when check or unckeck a Checkbox. I want to replicate this Textbox in a different window. I thought with Data Min

Answer 1

You will have to pass a reference to either the first window or the object that you're updating the text property on to the second window, it's DataContext property will do for that, you can then bind the second windows controls to it.

In this demo application I've created a MainWindow and a second window (Window1), the application starts in Main window like this.

MainWindow.xaml.cs

public partial class MainWindow : Window
{
    public string TestString
    {
        get { return (string)GetValue(TestStringProperty); }
        set { SetValue(TestStringProperty, value); }
    }

    public static readonly DependencyProperty TestStringProperty =  DependencyProperty.Register("TestString", typeof(string), typeof(MainWindow), new UIPropertyMetadata(null));

    public MainWindow()
    {
        InitializeComponent();

        // setup the test string.
        TestString = "this is a test.";

        // Create the second window and pass this window as it's data context.
        Window1 newWindow = new Window1()
        {
            DataContext = this
        };
        newWindow.Show();
    }
}

MainWindow.xaml - Take note of the DataContext line in the Window declaration.

<Window x:Class="WpfApplication5.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        DataContext="{Binding RelativeSource={RelativeSource Self}}"
        >
    <Grid>
        <TextBox Text="{Binding TestString, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Margin="91,84,185,189" />
    </Grid>
</Window>

Now for Window1 the code behind is just an empty default window class so I won't post it but the xaml is.

Window1.xaml

<Window x:Class="WpfApplication5.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window1" Height="300" Width="300">
    <Grid>
        <TextBlock Text="{Binding TestString, UpdateSourceTrigger=PropertyChanged}"/>
    </Grid>
</Window>

Answer 2

A couple of things wrong here, but I can probably give you a quick solution to fix your problem. First off your DataContext on window 2 isn't working properly, you can set it exclusively in your code right before you show window1...

private void button1_Click(object sender, RoutedEventArgs e)
{
    Window1 nueva = new Window1();
    this.DataContext = nueva.prueba;
    nueva.Show();
}

Next you have to fire INotifyPropertyChanged in your Texto class...

public class Texto : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    string name;
    public string Name
    {
        get { return this.name; }
        set 
        { 
            this.name = value; 
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs("Name"));
        }
    }

     public Texto( ) {}
     public Texto(string name) 
     {
        this.name = name;
     }

}

Answer 3

Don't set the DataContext explicitly, or only via another Binding. Your

<TextBox DataContext="prueba"

does nothing helpful. DataContext will be inherited as long as it is not overwritten. Don't set it explicitly. It should be enought to set it once on both windows.

Create your data object in your MainWindow

Texto prueba = new Texto("Carlos");
Window1 nueva = new Window1();
nueva.DataContext = prueba;
nueva.Show();

and remove all the other DataContext assignments.

Answer 4

If both textboxes share a common datacontext it will "just work" without any code required...