Strings in C#: == vs .Equals
I've heard a few times that .Equals is better than == for comparing strings in C#. To test this, I wrote a little C# program that called == a hundred million times, and then compared it with .Equals.
Here's the code:
string a = "hello";
string b = "hello";
int count = 0;
DateTime start = DateTime.Now;
for (int i=0; i<100000000; i++)
{
if (a.Equals(b))
count++;
else
count++;
};
TimeSpan ts = DateTime.Now - start;
Console.WriteLine("{0}", ts.Milliseconds);
The results were interesting.. I did the test four times, twice changing the strings so they were not equal (changing string “b” to “jello” from “hello”) and twice using == instead of .Equals.
Here's the results:
| a == b | a.Equals(b) |
|---|---|---|
| Equal strings | 961ms | 655ms |
| Differing strings | 750ms | 890ms |
So “a == b” is much slower when the strings are identical, and somewhat faster when the strings are different. But either way, I could compare these strings a hundred million times in less than a second. Another way to look at it is == is about 90% as fast as .Equals, on average (assuming your strings are the same about half the time).
Personally I think the difference is negligible and I prefer the readability of ==, but for performance-critical code it would make sense to think about whether you expect the strings to match or not match most of the time and choose the right one accordingly.