private static DrawManager instance

internal static DrawManager Instance
{
    get
    {
        if (instance == null)
	{
	    // Needs to be created via factory to make sure we only do this once
  	    instance = Factory.Create<DrawManager>();
	}
	return instance;
    } // get
}

private static DrawManager[] instances;

public static DrawManager Instance
{
    get
    {
        return Instances((RenderLayer)((MaterialManager.layers.Length - 1) / BaseMaterial.NumberOfBlendModes));
    } // get
}

public static DrawManager Instances(RenderLayer drawLayer)
{
    // If we have not yet created our DrawManager array, do so now
    if (instances == null) instances = new DrawManager[(MaterialManager.layers.Length / BaseMaterial.NumberOfBlendModes)];

    // If we have not yet created our DrawManager instance for this renderlayer, do so now
    if (instances[(int)drawLayer] == null) instances[(int)drawLayer] = Factory.Create<DrawManager>(drawLayer);

    // Return the appropriate DrawManager
    return instances[(int)drawLayer];
}

protected DrawManager(RenderLayer drawLayer)
    : base("DrawManager", typeof(MaterialManager))
{
    try
    {
	// The line material is an empty material with just the shader.
	// Note: 2D and 3D Positions are different in vertex data, both use
	// pretty much the same shader, but we need to 2 materials anyway.
	line2DMaterial = new Material((Texture)null, Shader.Create(
  	    // Note: This even works for VertexCompression because the Content.xml
	    // does save the original shader flags, not the modified ones in the
	    // case the VertexFormat of the shader uses vertex compression!
	    ShaderFeatureFlags.Basic |
	    ShaderFeatureFlags.UI2D |
	    ShaderFeatureFlags.NoTexturing |
	    ShaderFeatureFlags.ColoredVertices))
	    {
		    // Make sure that we always see the lines and aren't hidden by any
		    // "normal" geometry because the lines are usually used as debug
		    // information
		    // DrawLayer = (RenderLayer)((MaterialManager.layers.Length - 1) /
		    //	    BaseMaterial.NumberOfBlendModes)
                
		    // Assign the prescribed draw layer
		    DrawLayer = drawLayer,
	    };
...
}

public static void DrawOutline(Rectangle rect, Color lineColor)
{
    DrawOutline(rect, lineColor, (RenderLayer)((MaterialManager.layers.Length - 1) / BaseMaterial.NumberOfBlendModes));
}

public static void DrawOutline(Rectangle rect, Color lineColor, RenderLayer drawLayer)
{
    // Skip if the drawArea is certainly outside of the quadratic space.
    // Checking the screen area would work too, but is a little slower and
    // won't exclude much more anyway.
    if (rect.Left >= 1.0f ||
        rect.Top >= 1.0f ||
        rect.Left < -rect.Width ||
        rect.Top < -rect.Height)
    {
	// Skip this material rendering, not visible this frame.
	return;
    }

    DrawManager drawInstance = DrawManager.Instances(drawLayer);

    Point topRight = rect.TopRight;
    Point bottomRight = rect.BottomRight;
    Point bottomLeft = rect.BottomLeft;

    drawInstance.Draw2DLine(ref rect.TopLeft, ref topRight, ref lineColor);
    drawInstance.Draw2DLine(ref topRight, ref bottomRight, ref lineColor);
    drawInstance.Draw2DLine(ref bottomRight, ref bottomLeft, ref lineColor);
    drawInstance.Draw2DLine(ref bottomLeft, ref rect.TopLeft, ref lineColor);
}