Programmatic Binding to Presentation Controls in C#

Windows Presentation Foundation (WPF) offers many advances over WinForms. One of the most important features is data binding. This is a concept in the Model View ViewModel (MVVM) design patten that separates the responsibility of User Interface (UI) / View logic with Business / ViewModel logic.

Programmatic binding offers a slight advantage over XAML in that it will check the property names at compile time. With XAML, the binding path property names are evaluated at run time.

First, being with a ViewModel - or a ViewModelBase.

public abstract class ViewModelBase : DependencyObject, INotifyPropertyChanged
{
	private string _message;

	/// <summary>
	///     Gets or sets the message.
	/// </summary>
	/// <value>
	///     The message.
	/// </value>
	public string Message
	{
		get { return _message; }
		set { SetField(ref _message, value); }
	}

	public event PropertyChangedEventHandler PropertyChanged;

	public virtual void RaisePropertyChanged(string propertyName = null)
	{
		OnPropertyChanged(propertyName);
	}

	protected virtual void OnPropertyChanged(string propertyName = null)
	{
		PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
	}

	protected bool SetField<T>(ref T field, T value, [CallerMemberName] string propertyName = null)
	{
		if (!EqualityComparer<T>.Default.Equals(field, value))
		{
			field = value;
			OnPropertyChanged(propertyName);
			return true;
		}
		return false;
	}
}

Make sure to identify the MainGrid in the .xaml portion of the UserControl. For this example, we will define a MessageTextBox as well.

<UserControl x:Class="DemonstrationApp.UserControlView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:DemonstrationApp"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid x:Name="MainGrid" Margin="5">
		<TextBox x:Name="MessageTextBox">	
		</TextBox>
	</Grid>
</UserControl>

Next, in the xaml.cs file, set the view model and hook up the binding.

/// <summary>
///     Interaction logic for UserControlView.xaml
/// </summary>
public partial class UserControlView : UserControl
{
	/// <summary>
	///     The string for the ViewModel resource key
	/// </summary>
	private static readonly string ViewModelKey = "ViewModelKey";

	/// <summary>
	///     Gets or sets the view model.
	/// </summary>
	/// <value>
	///     The view model.
	/// </value>
	public ViewModelBase ViewModel
	{
		get { return (ViewModelBase) Resources[ViewModelKey]; }
		set
		{
			if (value != null && Resources != null)
			{
				Resources[ViewModelKey] = value;
				MainGrid.DataContext = ViewModel;
			}
		}
	}
	
	public UserControlView()
	{
		InitializeComponent();
		ViewModel = new ViewModelBase();
		
		// Set the binding
		BindingOperations.SetBinding(MessageTextBox, 
			TextBox.TextProperty, 
			new Binding(nameof(ViewModel.Message))
		{
			Source = ViewModel,
			Path = new PropertyPath(nameof(ViewModel.Message)),
			Mode = BindingMode.TwoWay,
			UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged
		});
	}
}

If you put a break point in the SetField method of the ViewModelBase, you will see binding to the Message property.