C# Wishlist: Null-Safe Dereferencing

During tests of a web application I came across a runtime error cause by the line:

var startUrl = Request.UrlReferrer.AbsoluteUri;

From within the application, the line works fine. However, if you paste the current URL into the address bar and hit Enter, it will cause a NullReferenceException. The obvious solution is to rewrite as

string startUrl = null;
if (Request.UrlReferrer != null)
    startUrl = Request.UrlReferrer.AbsoluteUri;

Suddenly I *knew* I wanted that null-safe dereferencing operator everybody is talking about:

• Null Safe Dereferencing (-> operator)

• Shorthand for nested null checking C#

• “Safe Navigator” operator ?.

• Groovy Safe Navigation Operator

• MS Connect request

Personally I prefer the ?. notation to -> or ??? I found elsewhere:

var startUrl = Request?.UrlReferrer?.AbsoluteUri;

This answer on SO illustrates a solution that is currently possible, but a bit verbose for my taste:

R NotNull<T, R>(this T src, Func<T, R> f)
      where T : class
      where R : class
{
    return src != null ? f(src) : null;
}

The class constraint on R is not necessary if you replace null with default(R):

R NotNull<T, R>(this T src, Func<T, R> f)
      where T : class
{
    return src != null ? f(src) : default(R);
}

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