System.MemoryExtensionsPolyfills static class MemoryExtensionsPolyfills Provides downlevel polyfills for span extension methods. Documentation Code public static bool Contains<T>(this ReadOnlySpan<T> span, T value) where T : IEquatable<T> public static bool ContainsAny(this ReadOnlySpan<char> span, ReadOnlySpan<char> values) public static bool ContainsAnyExcept(this ReadOnlySpan<char> span, char value)