Update binding

How to bind command to a button I explained here.

Here is my XAML:

<Window x:Class="UpdateBinding.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:viewModel="clr-namespace:UpdateBinding.ViewModel"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <viewModel:UpdateBindingViewModel x:Key="UpdateBindingBindingViewModel" />
    </Window.Resources>
    <Grid DataContext="{StaticResource UpdateBindingBindingViewModel}">
        <StackPanel>
            <TextBox Name="MyTextBox" Text="{Binding Ubm.Name}" VerticalAlignment="Top"/>
            <Button VerticalAlignment="Top" Command="{Binding OnButtonClick}">test</Button>
        </StackPanel>
    </Grid>
</Window>

Command to update value looks like this:

public void UpdateBinding(object obj)
{
  Ubm.Name = "Updated value";
  OnPropertyChanged(() => this.Ubm);
}

Part of code:

protected void OnPropertyChanged<T>(Expression<Func<T>> property)
{
  if (this.PropertyChanged != null)
  {
	var mex = property.Body as MemberExpression;
	string name = mex.Member.Name;
	this.PropertyChanged(this, new PropertyChangedEventArgs(name));
  }
}

I took from here.

Also don't forget to implement INotifyPropertyChanged interface, in my case declaration of viewmodel looks like this:

public class UpdateBindingViewModel: INotifyPropertyChanged

Example application you can download from here.

---

2014-06-11 Update Just a short notice. If you implement interface by default (with resharper alt + enter :) ) then to use it, you have to write which property of class (view model) are you updating. Something like:

[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
	PropertyChangedEventHandler handler = PropertyChanged;
	if (handler != null)
	{
		handler(this, new PropertyChangedEventArgs(propertyName));
		if (propertyName == "test")
		{
			MyHidden = !MyHidden;
			myContent = "Clicked!";
		}
	}
}

Where OnPropertyChanged is called like this:

OnPropertyChanged("MyHidden");

Obviously this example is not compatible with previous example :) I hope I will update this article soon...

---

2014-06-13 Another update

Check out following code:

namespace BooleanToVisibilityConverterExample.ViewModel
{
  using System.ComponentModel;
  using System.Runtime.CompilerServices;
  using System.Windows;
  using System.Windows.Input;

  using BooleanToVisibilityConverterExample.Annotations;

  public class BooleanToVisibilityConverterExampleViewModel: INotifyPropertyChanged
  {
    public ICommand OnClick { get; set; }
    public bool MyHidden { get; set; }

    public BooleanToVisibilityConverterExampleViewModel()
    {
      OnClick = new RelayCommand(ShowHide);
      MyHidden = true;
    }

    private void ShowHide(object obj)
    {
      MyHidden = !MyHidden;
      OnPropertyChanged("MyHidden");
    }

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
      var handler = PropertyChanged;
      if (handler != null)
      {
        handler(this, new PropertyChangedEventArgs(propertyName));
      }
    }
  }
}

Here notice lines:

MyHidden = !MyHidden;
OnPropertyChanged("MyHidden");

With these lines I said that I want to update property MyHidden which is bounded to rectangle visibility. This update actually is coming from this article, and example you can download from here.