A comment on a recent post of mine on Stack Overflow suggested that I replace my "for" loop with a more "modern" version using "foreach" and Enumerable.Range. In other words:

// replace this
for (int i = 0; i < 1000; i++)
{
}

// with this
foreach (var i in Enumerable.Range(0, 1000))
{
}

 

I can't really say that I prefer one over the other, although the second approach does look kinda cool. It'd be even nicer if there were some native support for ranges in C# like there was in Pascal:

// borrowing Pascal's range syntax
foreach (var i in [0..1000])
{
}

... but I digress. What I wanted to talk about in this post is my findings on the performance difference between a simple "for" loop and a "foreach" over Enumerable.Range. I timed two long loops using a Stopwatch:

const int count = 100000000;
var sw = new Stopwatch();

sw.Reset();
sw.Start();
for (int i = 0; i < count; i++)
{
}
sw.Stop();
var forTime = sw.ElapsedTicks;

sw.Reset();
sw.Start();
foreach (var i in Enumerable.Range(0, count))
{
}
sw.Stop();
var foreachTime = sw.ElapsedTicks;

Console.WriteLine(forTime);
Console.WriteLine(foreachTime);
Console.WriteLine((float)foreachTime / forTime);

 

The result:

4869915
14286932
2.933713

So the Enumerable.Range approach is three times slower than a simple for loop.

I guess in a real-world situation where the body of the loop is the thing taking the bulk of the time, there wouldn't be that big a difference, but it's interesting that the two approaches differ in performance by so much. Something to be aware of if you're very performance-oriented in your code, anyway.