How to check for nulls in a deep lambda expression? [duplicate]

Answer 1

You could modify your getters to read something like:

private Two _two;
public Two Two
{
     get 
     {
       if (null == _two)
         return new Two();
       else
         return _two;
      }
}

Answer 2

Always initialize your properties before using them. Add a constructor to class One, Two, Three and Four. In the constructor initialize your properties so they are not null.

Answer 3

I'm not skilled in c#, but maybe there's some way to implement the "andand" pattern from ruby that solves exactly this problem without polluting the implementation.

The concept is also known as the Maybe Monad in Haskell.

The title of this article seems promising.

Answer 4

I find the coalesce operator useful for this at times. This only helps though if there is a default/null equivalent version of the object you can drop in.

For instance, sometimes when I'm cracking open XML...

IEnumeratable<XElement> sample;
sample.Where(S => (S.Attribute["name"] ?? new XAttribute("name","")).Value.StartsWith("Hello"))...

Depending on how the default objects are retrieved this can be verbose, and the above example is not a great use but you get the idea. For the particular case of reading XML attributes I have an extension method that returns the attribute value or an empty string.