Can I force my own short-circuiting in a method call?

Question

Suppose I want to check a bunch of objects to make sure none is null:

if (obj != null &&
    obj.Parameters != null &&
    obj.Parameters.UserSet         


        

Answer 1

You could write a function that accepts an expression tree and transforms that tree into a form that will check for nulls, and return a Func that could be safely evaluated to determine if there is a null.

I suspect that while the resulting code may be cool, it would be confusing, and much less performant than just writing a bunch of short-circuited a != null && a.b != null... checks. In fact, it would likely be less performant than just checking all the values and catching the NullReferenceException (not that I advocate for exception handling as a flow of control mechanism).

The signature for such a function would be something like:

public static Func NoNulls( Expression> expr )

and it's usage would look something like:

NoNulls( () => new { a = obj, 
                     b = obj.Parameters, 
                     c = obj.Parameters.UserSettings } )();

If I get some free time, I will write a function that does just such an expression tree transformation and update my post. However, I'm sure that Jon Skeet or Mark Gravell could write such a function with one eye closed and one hand behind their back.

I would also love to see C# implement the .? operator that Eric alludes to. As a different Eric (Cartman) might say, that would "kick ass".