[C#][OpenGL] Maintain aspect ratio when resizing window

ReshapeWindow.cs

		/// <summary>
		///     Reshapes the drawing are to maintain aspect ratio when the window is resized,
		///     using a target pixel ratio to maintain, and applying "pillars" or "letterbox"
		///     effect as needed, allowing the drawing context to shrink/grow uniformly.
		/// </summary>
		/// <param name="width">The new width of the window/drawing area to fit to.</param>
		/// <param name="height">The new height of the window/drawing area to fit to.</param>
		public void WindowReshape(int width, int height)
		{
			// Make the projection matrix active
			Gl.MatrixMode(MatrixMode.Projection);
			Gl.LoadIdentity();
			// The "Graphics" width and height contain the desired pixel resolution to keep.
			Gl.Ortho(0.0, Graphics.Width, Graphics.Height, 0.0, 1.0, -1.0);
			// Calculate the proper aspect ratio to use based on window ratio
			var ratioX = width / (float) Graphics.Width;
			var ratioY = height / (float) Graphics.Height;
			var ratio = ratioX < ratioY ? ratioX : ratioY;
			// Calculate the width and height that the will be rendered to
			var viewWidth = Convert.ToInt32(Graphics.Width * ratio);
			var viewHeight = Convert.ToInt32(Graphics.Height * ratio);
			// Calculate the position, which will apply proper "pillar" or "letterbox" 
			var viewX = Convert.ToInt32((width - Graphics.Width * ratio) / 2);
			var viewY = Convert.ToInt32((height - Graphics.Height * ratio) / 2);
			// Apply the viewport and switch back to the GL_MODELVIEW matrix mode
			Gl.Viewport(viewX, viewY, viewWidth, viewHeight);
			Gl.MatrixMode(MatrixMode.Modelview);
			Gl.LoadIdentity();
		}