CODEWITHSUNDEEP
c#silverlightwindows-phone-7binding
Maku
Maku

Reputation: 389

Binding update problem

I have a problem with binding update when binding property is changed. Look at the code below. I will explain my issue in the following example. 

public class SettingsControl : INotifyPropertyChanged
    {

        string _value = "test";

        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged(string name)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(name));
            }
        }

        public SettingsControl() { }


     public string Value
        {
            get { return _value; }
            set { _value = value; OnPropertyChanged("Value"); }
        }
    }

<local:SettingsControl x:Key="Settings"></local:SettingsControl>

<TextBox Height="72" Text="{Binding Value, Mode=TwoWay, Source={StaticResource Settings} }"/>
<TextBlock Text="{Binding Value, Mode=OneWay, Source={StaticResource Settings} }" VerticalAlignment="Top" Width="135" />
<Button Height="100" Click="button1_Click" />

and code behind: 

private void button1_Click(object sender, RoutedEventArgs e)
    {
        SettingsControl settings = new SettingsControl();
        settings.Value = "new value";
    }

Now, when I change text in TextBox everything works just fine. New text is shown in TextBlock. But if I set new text in code to the settings.Value nothing happens.

What I suppose to do in order to change settings.Value in code and affect TextProperty in TextBlock.

EDIT: Solution below for those who had the same problem as me: 

    SettingsControl settings = (SettingsControl)this.Resources["Settings"];
    settings.Value = "new value";

Upvotes: 2

Views: 178

Answers (2)

Polhovskiy
Polhovskiy

Reputation: 329

You should try to make Mode=TwoWay ;-)

Upvotes: 0

Reed Copsey
Reed Copsey

Reputation: 564901

In your code behind, you're setting the value on a new instance, not on the instance being used.

Try changing the code behind to:

private void button1_Click(object sender, RoutedEventArgs e)
{
    // Set the Value on "this"
    this.Value = "new value";
}

That being said, properties on a "Control" are typically handled via making a Dependency Property, not via INotifyPropertyChanged. This allows them to be set and used correctly in XAML, and participate fully in binding in more scenarios.

Upvotes: 5

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