Question

My class has complicated property:

    private Image m_LogoImage=null;

    public Image LogoImage
    {
        get
        {
            if (m_LogoImage == null && File.Exists(Data.LogoFileUrl))
            {
                DrawingImage image = DrawingImage.FromFile(Data.LogoFileUrl);
                m_LogoImage = Image.GetInstance(image, new Color(1, 1, 1));
            }
            return m_LogoImage;
        }
    }

LogoImage.get is very slow and resource consuming action to the first time the client calls it, the property calculate the image and stored the result in private variable m_LogoImage.
This looks to me very basic. .NET support automatic properties (public string P {get;set;}). Does it support automatic storing of complicated properties?

Answer 1

There’re a number of state based concerns, so there’s no language level mechanics for lazy load.

You can however use the Lazy<T> class to accomplish this functionality.

 private Lazy<Image> logo = new Lazy(() => LoadImage()); 

 public Image LogoImage
    {
        get
        {
            return logo.Value;
        }
    }

You can also use the null coalescing operator (??) to do lazy load for nullable types.

get 
{
    return image ?? (image = LoadImage());
}