Question

Quick question here about short-circuiting statements in C#. With an if statement like this:

if (MyObject.MyArray.Count == 0 || MyObject.MyArray[0].SomeValue == 0)
{

//....
}

Is it guaranteed that evaluation will stop after the “MyArray.Count” portion, provided that portion is true? Otherwise I’ll get a null exception in the second part.

Answer 1

Yes, this is guaranteed.

C# Language Specification – 7.11 Conditional logical operators:

The && and || operators are called the conditional logical operators. They are also called the “short-circuiting” logical operators.

Therefore they will support logical short-circuiting by definition – you can rely on this behavior.

Now it is important to make a distinction between a conditional operator and a logical operator:

• Only conditional operators support short-circuiting, logical operators do not.
• C#’s logical operators look just like their conditional counterparts but with one less character so a logical OR is | and a logical AND is &.
• Logical operators can be overloaded but conditional operators cannot (this is a bit of an technicality as conditional operator evaluation does involve overload resolution and this overload resolution can resolve to a custom overload of the type’s logical operator, so you can work around this limitation to a certain extent).