Checkbox binding example

MainWindow.xaml

<Window x:Class="TestApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:testApp="clr-namespace:TestApp"
        Title="MainWindow" Height="350" Width="525">
    <Window.DataContext>
        <testApp:MainWindowViewModel />
    </Window.DataContext>
    <Grid>
        <StackPanel>
            <CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}"/>
            <TextBox Text="{Binding Text}" />
        </StackPanel>
    </Grid>
</Window>

MainWindowViewModel.cs

namespace TestApp
{
	using System.ComponentModel;

	public class MainWindowViewModel : INotifyPropertyChanged
	{
		private bool _isChecked;
		private string _text;

		public bool IsChecked 
		{
			get { return _isChecked; }
			set
			{
				_isChecked = value;
				if (_isChecked)
				{
					Text = "Hello!";
				}
				else if (!_isChecked)
				{
					Text = string.Empty;
				}
				RaisePropertyChanged("IsChecked");
			} 
		}

		public string Text
		{
			get { return _text; }
			set { _text = value; RaisePropertyChanged("Text"); } 
		}

		public MainWindowViewModel()
		{
			
		}

		// Property Changed Event Handlers
		public event PropertyChangedEventHandler PropertyChanged;
		protected void RaisePropertyChanged(string propertyName)
		{
			var handler = PropertyChanged;
			if (handler != null)
				handler(this, new PropertyChangedEventArgs(propertyName));
		}
	}
}