Nested or not nested if-blocks?

Question

I was wondering if there is a performance difference when using ifs in C#, and they are nested or not. Here's an example:

if(hello == true) {
    if(index == 34) {
        DoSomething();
    }
}

Is this faster or slower than this:

if(hello == true && index == 34) {
    DoSomething();
}

Any ideas?

Answer 1

Probably the compiler is smart enough to generate the same, or very similar code, for both versions. Unless performance is really a critical factor for your application, I would automatically choose the second version, for the sake of code readability.

Answer 2

Even better would be

if(SomethingShouldBeDone()) {
    DoSomething();
}

...meanwhile in another part of the city...

private bool SomethingShouldBeDone()
{
    return this.hello == true && this.index == 34;
}

In 99% of real-life situations this will have little or no performance impact, and provided you name things meaningfully it will be much easier to read, understand and (therefore) maintain.