Shorthand for nested null checking C#

Question

As far as I know there is not a significantly more elegant way to write the following....

string src;
if((ParentContent!= null)
    &&am         


        

Answer 1

It still leaves a bit to be desired but I'd write it like this:

var src = ParentContent == null ? null
    : ParentContent.Image("thumbnail") == null ? null
    : ParentContent.Image("thumbnail").Property("src") == null ? null
    : ParentContent.Image("thumbnail").Property("src").Value;

Answer 2

There is no built-in syntax for doing this, but you can define an extension method to do this:

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

Now, you can rewrite your example as follows:

src = ParentContent.NotNull(p => p.Image("thumbnail")).
        NotNull(i => i.Property("src")).NotNull(src => src.Value);

It is not as nice as it may be with a syntactic support, but I'd say it's much more readable.

Note that this adds the NotNull method to all .NET types, which may be a bit inconvenient. You could solve that by defining a simple wrapper type WrapNull<T> where T : class containing only a value of type T and a method for turning any reference type into WrapNull and providing the NotNull in the WrapNull type. Then the code would look like this:

src = WrapNull.Wrap(ParentContent).NotNull(p => p.Image("thumbnail")).
        NotNull(i => i.Property("src")).NotNull(src => src.Value);

(So you wouldn't pollute the IntelliSense of every type with the new extension method)

With a bit more effort, you could also define a LINQ query operators for doing this. This is a bit overkill, but it is possible to write this (I won't include the definitions here as they are a bit longer, but it's possible in case someone is interested :-)).

src = from p in WrapNull.Wrap(ParentContent)
      from i in p.Image("thumbnail").
      from src in i.Property("src")
      select src.Value;

Answer 3

It's been suggested and apparently rejected by the team:

A bit more C# syntactic sugar for nulls

The proposed syntax would have looked like a.?b.?c() - very useful, and unambiguous.

I'd really like to see it too, but doesn't look like it'll happen. Maybe if enough people vote on it!

Answer 4

We considered it for C# 4 but did not have the budget. It's a nice feature that a lot of people request, so perhaps we'll get it into a future hypothetical language version. No promises.

Answer 5

Correct me, if I am wrong, but this could be solved using C# 6.0's null-conditional operator:

string src = ParentContent?.Image("thumbnail")?.Property("src")?.Value;

If src is already in used before this value assignment, you could use it as follows:

string src = ....;

// ...

src = ParentContent?.Image("thumbnail")?.Property("src")?.Value ?? src;

// ...