Binding in TextBlock doesn't work in WPF

Question

I want to dynamically change TextBlock text in my Class.

XAML-Code:

<TextBlock Name="Footer_text"  Text=""/>

C#:

string footerMainMenuText = "Setting";
Binding  set = new Binding("");
set.Mode = BindingMode.OneWay;
set.Source = footerMainMenuText;
Footer_text.DataContext = footerMainMenuText;
Footer_text.SetBinding(TextBlock.TextProperty, set);

I checked last line, and the Footer_text.Text is set correctly. ( Footer_text.Text="Setting"), but TextBlock in my application doesnt show "Setting". What is the problem here?

Jewelry

Have you tried removing the Text="" from the XAML? – Cabala

Answer 1

If you are binding - why not just do it in XAML instead? Looking at your code it's kind of pointless - you might as well just go

Footer_text.Text = "Setting";

You should ideally do it in XAML or at least provide something for it to bind to

<TextBlock Text="{Binding SomeProperty}" />

I'm not sure why you would bind a 'string' on it's own to anything...do you have an object which you need to bind to the text property?

Also using

Binding("")

What does that do? A blank path? Not sure what the binding target would be there... have you tried

Binding()

instead?

Edit:

Also the reason why your binding is not updating the control, is probably because you haven't bound to an object which implements INotifyPropertyChanged or a similar interface. The controls need to know when values have changed, so I'd imagine that binding to 'string' isn't giving the TextBlock the proper notification when it changes

Edit 2:

Here is a quick example of binding working:

My window class Window.cs:

<Window x:Class="WpfApplication1.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">
    <Grid>
        <StackPanel>
        <TextBlock x:Name="txtName" Text="{Binding Name}"></TextBlock>
            <Button Click="Button_Click">Click me 1</Button>
            <Button Click="Button_Click_1">Click me 2</Button>
        </StackPanel>
    </Grid>
</Window>

The code behind in Window.xaml.cs

public partial class MainWindow : Window
{
    SomeObjectClass obj = new SomeObjectClass();
    public MainWindow()
    {
        InitializeComponent();

        txtName.DataContext = obj;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        obj.Name = "Hello World";
    }

    private void Button_Click_1(object sender, RoutedEventArgs e)
    {
        obj.Name = "Goobye World";
    }
}

The object to bind to (with INotifyPropertyChanged)

class SomeObjectClass : INotifyPropertyChanged
{
    private string _name = "hello";
    public string Name
    {
        get
        {
            return _name;
        }
        set
        {
            _name = value;
            OnPropertyChanged("Name");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

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

Clicking the buttons changes SomeObject.Name, but it updates the textbox.

Jake

thanks,your code work great. but for my application doestn work correctly. I have three class: (Window)MainWindow, (class)SomeObjetcClass and (Window)test. SomeObjectclass is like your class. Move this two Buttons from MainWindow to test. MainWindows included only TextBlock. then it doestn work. if i click Button click me 1 from test-class, the text hello doesnt change. what should i change in your code so that control textblock from another class(test.cs) by clicking button in this class? – Jewelry

It sounds like you need some tuition - are you new to programming/c#? Basically - if you want to change the value from test.cs, you need to make the 'obj' variable public and pass the MainWindow instance to test.cs so you can reference the obj variable. I think doing this is maybe outside the scope of what StackOverflow is for :P – Jake