Think LINQ – .SequenceEqual()

Up until March 26, I had come up with a number of crazy concoctions to test whether one IEnumerable<> was equal to another. Some of them chained together .Intersect() with .Count(), comparing the count of the elements in the intersected set with the count of the elements in each of the two sets. (If the count of A∩B is equal to the count of A and the count of B, then A and B are equal.)

That method was mostly rubbish.

What I have since learned is that there is a relatively efficient LINQ operator called .SequenceEqual() that compares two ordered IEnumerable<>s. If each of the IEnumerable<>s contain equal elements in the same order, the IEnumerable<>s are equal. Simple. Straightforward. Useful.

IEnumerable<string> stringsTheFirst = new string[] { "one", "two", "three" };
IEnumerable<string> stringsTheSecond = new string[] { "one", "two", "three" };
bool stringsAreEqual = stringsTheFirst.SequenceEqual(stringsTheSecond);

And if your IEnumerable<>s are not already ordered for you, the pattern then becomes:

IEnumerable<string> stringsTheFirst = new string[] { "two", "one", "three" };
IEnumerable<string> stringsTheSecond = new string[] { "one", "two", "three" };
bool stringsAreEqual = stringsTheFirst.OrderBy(s => s).SequenceEqual(stringsTheSecond.OrderBy(s => s));