IEqualityComparer for SequenceEqual
There is no such comparer in .NET Framework, but you can create one:
public class IEnumerableComparer<T> : IEqualityComparer<IEnumerable<T>>
{
public bool Equals(IEnumerable<T> x, IEnumerable<T> y)
{
return Object.ReferenceEquals(x, y) || (x != null && y != null && x.SequenceEqual(y));
}
public int GetHashCode(IEnumerable<T> obj)
{
// Will not throw an OverflowException
unchecked
{
return obj.Where(e => e != null).Select(e => e.GetHashCode()).Aggregate(17, (a, b) => 23 * a + b);
}
}
}
In the above code, I iterate over all items of the collection in the GetHashCode
. I don't know if it's the wisest solution but this what is done in the internal HashSetEqualityComparer
.
Created a NuGet package based on Cédric Bignon's answer:
Assembly package: https://www.nuget.org/packages/OBeautifulCode.Collection/
Code-file-only package: https://www.nuget.org/packages/OBeautifulCode.Collection.Recipes.EnumerableEqualityComparer/
var myEqualityComparer = new EnumerableEqualityComparer<string>();