c# - Boolean Or containing Ternary conditional operation doesn't get short-circuited

Question

In general, the short circuit or operator || ignores the right side of the or if the left side evaluates to true. Apparently, we've found an exception to this.

Check out the following:

if (foo == null || bar != true ? foo.Count == 0 : true)
{

}

This code throws a null reference exception on the command foo.Count because foo is null. And naturally, the boolean logic allows for this. But, if foo is null you would expect that the or would short circuit and not even evaluate the right side of the expression, but it still does, and it throws an exception.

Is this a bug in my code or in the C# compiler? Is there a part of the C# specification that handles this case?

Answer 1

That's because your statement isn't being evaluated as you expect.

You need some extra parenthesis:

if(foo == null || (bar != true ? foo.Count == 0 : true))

The way it's written now is equivalent to (due to operator precedence):

if((foo == null || bar != true) ? foo.Count == 0 : true)