Bind a property to another property in C#

Question

I have a Class called Grid that is composed of two other classes: Circle and Line. Here is the code for these classes:

public class Grid
{
    public Circle Circle {get; set;}
    public Line Line {get; set;}
}

I want the geometry of Line to stay connected to the geometry of the Circle. This means that when I move the Circle, I want the Line to be notified and update its geometry to match the new location of the Circle. I could create a new Grid with the updated geometries of the Circle and Line, but I don't want to create a new Grid. Instead, I want to bind the endpoints of the Line to the Circle, for example to its center.

What technologies in C# can I use to achieve this? Are delegates or the INotifyPropertyChanged interface suitable for this purpose?

Answer 1

public class Circle : INotifyPropertyChanged
{
    private int radius;       
    public int Radius 
    {
        get { return radius; }
        set 
        {
            radius = value;
            RaisePropertyChanged("Radius");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void RaisePropertyChanged(string propertyName)
    {
        var propChange = PropertyChanged;
        if (propChange == null) return;
        propChange(this, new PropertyChangedEventArgs(propertyName));
    }
}

Then in Grid.cs

public class Grid
{
    private Circle circle;
    public Circle Circle 
    {
       get { return circle; }
       set 
       {
           circle = value;
           if (circle != null) 
              circle.PropertyChanged += OnPropertyChanged;
       }
    }

    private void OnPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "Radius")
            // Do something to Line
    }
}