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C# SequenceEqual Method (If Two Arrays Are Equal)

Use the SequenceEqual extension method from System.Linq to compare two collections.
SequenceEqual. Are two sequences the same? With the SequenceEqual extension from System.Linq in the C# language, you can test 2 collections for equality in one statement.
SequenceEqual compares 2 collections for exact equality. Its performance is much worse than alternative implementations. We look at the SequenceEqual method.LINQ
First example. We allocate 4 string arrays on the managed heap. Next, the SequenceEqual method is used on the arrays: array1 is tested against array2, array3, and array4.Array

Info: The variable array1 was determined not to be equal to array2. But Array1 was equal to array3.

And: Array1 was equal to array4 when the IEqualityComparer implementation (StringComparer.OrdinalIgnoreCase) was specified.

StringComparison, StringComparer

OrdinalIgnoreCase: This causes the elements to be equal if they only have different cases. The character casing is ignored.

C# program that uses SequenceEqual using System; using System.Linq; class Program { static void Main() { string[] array1 = { "dot", "net", "perls" }; string[] array2 = { "a", "different", "array" }; string[] array3 = { "dot", "net", "perls" }; string[] array4 = { "DOT", "NET", "PERLS" }; bool a = array1.SequenceEqual(array2); bool b = array1.SequenceEqual(array3); bool c = array1.SequenceEqual(array4, StringComparer.OrdinalIgnoreCase); Console.WriteLine(a); Console.WriteLine(b); Console.WriteLine(c); } } Output False True True
Benchmark. Methods found in System.Linq usually have worse performance on arrays than custom imperative algorithms. I tested the performance of SequenceEqual.

Version 1: This version of the code uses SequenceEqual to compare 2 larger-sized integer arrays.

Int Array

Version 2: Here we use a for-loop method called ArraysEqual to compare the arrays.

For

Result: SequenceEqual was more than ten times slower than the imperative algorithm (ArraysEqual).

Note: It's good to keep in mind that SequenceEqual on large equal arrays is more than ten times slower than a loop.

C# program that benchmarks SequenceEqual using System; using System.Diagnostics; using System.Linq; class Program { static void Main() { const int max = 10000; var a1 = Enumerable.Range(0, short.MaxValue).ToArray(); var a2 = Enumerable.Range(0, short.MaxValue).ToArray(); var s1 = Stopwatch.StartNew(); // Version 1: use SequenceEqual. for (int i = 0; i < max; i++) { bool equals = a1.SequenceEqual(a2); } s1.Stop(); var s2 = Stopwatch.StartNew(); // Version 2: use custom method. for (int i = 0; i < max; i++) { bool equals = ArraysEqual(a1, a2); } s2.Stop(); Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / max).ToString("0.00 ns")); Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / max).ToString("0.00 ns")); Console.Read(); } static bool ArraysEqual(int[] a1, int[] a2) { if (a1.Length == a2.Length) { for (int i = 0; i < a1.Length; i++) { if (a1[i] != a2[i]) { return false; } } return true; } return false; } } Output 515889.45 ns 36280.79 ns
A summary. SequenceEqual is an easy way to compare 2 arrays or other collections such as Lists for equality. Any argument to SequenceEqual must implement the IEnumerable interface.IEnumerableList
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