Extension method for succinct RectangleF mutation expressions.

RectangleExtensions.cs

public static class RectangleExtensions
{
  public static RectangleF With (this RectangleF self,
                                 float? X = null, float? Y = null,
                                 float? Width = null, float? Height = null)
  {
    return new RectangleF (X ?? self.X, Y ?? self.Y, Width ?? self.Width, Height ?? self.Height);
  }
  
  static T Id<T> (T t) { return t; }

  public static RectangleF With (this RectangleF self,
                                 Func<float,float> X = null, Func<float,float> Y = null,
                                 Func<float,float> Width = null, Func<float,float> Height = null)
  {
    return new RectangleF ((X ?? Id) (self.X), (Y ?? Id) (self.Y),
                          (Width ?? Id) (self.Width), (Height ?? Id) (self.Height));
  }
}

// Demo 1
UIView.Animate (0.5, () => {
  View.Frame = View.Frame.With (Width: 200, Y: 50);
});

// Demo 2
UIView.Animate (0.5, () => {
  View.Frame = View.Frame.With (Y: y => y - 100);
});