UPDATE: A commenter points out that today is the 200th anniversary of the birth of George Boole; I had no idea when I scheduled this article that it would be so apropos. Happy birthday George Boole!

Here’s a little-known and seldom-used fact about C# operators: you can apply the & and | operators to bools, not just to integers. The & and | operators on bools differ from && and || in only one way: both operators always “eagerly” evaluate both operands. This is in marked contrast to the “lazily” computed evaluation of the && and || operators, which only evaluate their right hand argument if needed. Why on earth would you ever want to evaluate the right hand side if you didn’t need to? Why have this operation at all on bools?

A few reasons come to mind. First, sometimes you want to do two operations, and know whether both of them succeeded: Continue reading →

In part one I gave a bunch of reasons to reject the proposed feature where the compiler infers additional type information about a local variable when inside the consequence of a conditional statement:

if (animal is Dog)
{
    animal.Bark(); 
    // instead of ((Dog)animal).Bark();
}

But the problem still remains that this is a fairly common pattern, and that it seems weird that the compiler cannot make the necessary inference.

A number of readers anticipated my denouement and made some of the same proposals I was going to make in this part. Let’s go through a few of them; see the comments to the previous article for a few more.

Continue reading →

In last week’s episode of FAIC I was discussing code of the form:

if (animal is Dog)
    ((Dog)animal).Bark();

Specifically, why the cast was illegal if the variable tested was of generic parameter type. Today I want to take a bit of a different tack and examine the question “why do we need to insert a cast at all?” After all, the compiler should know that within the consequence of the if, the variable animal is guaranteed to be of type Dog. (And is guaranteed to be non-null!) Shouldn’t the code simply be:

if (animal is Dog)
    animal.Bark();

Continue reading →

Hey everyone, I am finally back from my many travels this summer and looking forward to doing some blogging this autumn. I’ll post some vacation photos when I have them sorted out. Until then, here’s an article that the nice people at InformIT asked me to write: what are my ten least favourite C# features?

I’m sure I missed some of your least favourites; I’d love to know what your pet peeves are in the comments here or on the article itself.