I can't Data Bind to a local variable in WPF/XAML
Solution 1
Your current myText
property has no way of notifying the WPF binding system when its value has changed, so the TextBlock
wont be updated.
If you make it a dependency property instead it automatically implements change notification, and the changes to the property will be reflected in the TextBlock
.
So if you replace public string myText { get; set; }
with all of this code it should work:
public string myText
{
get { return (string)GetValue(myTextProperty); }
set { SetValue(myTextProperty, value); }
}
// Using a DependencyProperty as the backing store for myText. This enables animation, styling, binding, etc...
public static readonly DependencyProperty myTextProperty =
DependencyProperty.Register("myText", typeof(string), typeof(Window1), new PropertyMetadata(null));
Solution 2
implement INotifyPropertyChanged
:
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
this.InitializeComponent();
}
private string _txt;
public string txt
{
get
{
return _txt;
}
set
{
if (_txt != value)
{
_txt = value;
OnPropertyChanged("txt");
}
}
}
private void Button_Click(object sender, RoutedEventArgs e)
{
txt = "changed text";
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
XAML:
<TextBox Text="{Binding txt}"/>
<Button Click="Button_Click">yes</Button>
and don't forget about adding the DataContext property of your window:
<Window ... DataContext="{Binding RelativeSource={RelativeSource Self}}"/>
Solution 3
Try this:
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
this.DataContext = this;
}
public string myText { get; set; }
public void Button_Click_1(object sender, RoutedEventArgs e)
{
BackgroundWorker bw = new BackgroundWorker();
bw.DoWork += delegate
{
int i = 0;
for (i = 0; i < 100; i++)
{
System.Windows.Threading.Dispatcher.CurrentDispatcher.Invoke((Action)(() => { myText = i.ToString(); OnPropertyChanged("myText"); }));
Thread.Sleep(100);
}
};
bw.RunWorkerAsync();
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
XAML file:
<Grid>
<Button Content="Button" HorizontalAlignment="Left" Height="106" Margin="71,95,0,0" VerticalAlignment="Top" Width="125" Click="Button_Click_1"/>
<TextBlock x:Name="myTextBox"
HorizontalAlignment="Right" Height="106" Margin="0,95,46,0"
TextWrapping="Wrap" VerticalAlignment="Top" Width="187"
Text= "{Binding myText}" />
</Grid>
Solution 4
You should implement INotifyPropertyChanged
in your "MainWindow" so your "myTextBlock" can automatically pick up changes from your data and update.
So your "MainWindow" should look like:
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
}
private string _myText;
public string myText {
get{return _myText;}
set{_myText = value;
if(PropertyChanged!=null) PropertyChanged(this, new PropertyChangedEventArgs("myText")) ;
}
}
public event PropertyChangedEventHandler PropertyChanged;
etc.....
}
mzachen
Updated on June 04, 2022Comments
-
mzachen almost 2 years
I want a textbox to display the value of a variable when I click it (an iteration of 1 to 100), I do not know what I am doing Wrong:
When I run the project nothing is displayed in the text box.
What is the best way to display variables in a text box?
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows; using System.Windows.Controls; using System.Windows.Data; using System.Windows.Documents; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Imaging; using System.Windows.Navigation; using System.Windows.Shapes; namespace dataBindingTest { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); } public string myText { get; set; } public void Button_Click_1(object sender, RoutedEventArgs e) { int i = 0; for (i = 0; i < 100; i++) { myText = i.ToString(); } } } }
XAML:
<Window x:Class="dataBindingTest.MainWindow" Name="windowElement" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Grid> <Button Content="Button" HorizontalAlignment="Left" Height="106" Margin="71,95,0,0" VerticalAlignment="Top" Width="125" Click="Button_Click_1"/> <TextBlock x:Name="myTextBox" HorizontalAlignment="Left" Height="106" Margin="270,95,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="187" Text= "{Binding myText, ElementName=windowElement}" /> </Grid> </Window>