Reduce some allocations

MediaBrowser.Common/Extensions/EnumerableExtensions.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+
+namespace MediaBrowser.Common.Extensions
+{
+    /// <summary>
+    /// Static extensions for the <see cref="IEnumerable{T}"/> interface.
+    /// </summary>
+    public static class EnumerableExtensions
+    {
+        /// <summary>
+        /// Determines whether the value is contained in the source collection.
+        /// </summary>
+        /// <param name="source">An instance of the <see cref="IEnumerable{String}"/> interface.</param>
+        /// <param name="value">The value to look for in the collection.</param>
+        /// <param name="stringComparison">The string comparison.</param>
+        /// <returns>A value indicating whether the value is contained in the collection.</returns>
+        /// <exception cref="ArgumentNullException">The source is null.</exception>
+        public static bool Contains(this IEnumerable<string> source, ReadOnlySpan<char> value, StringComparison stringComparison)
+        {
+            if (source == null)
+            {
+                throw new ArgumentNullException(nameof(source));
+            }
+
+            if (source is IList<string> list)
+            {
+                int len = list.Count;
+                for (int i = 0; i < len; i++)
+                {
+                    if (value.Equals(list[i], stringComparison))
+                    {
+                        return true;
+                    }
+                }
+
+                return false;
+            }
+
+            foreach (string element in source)
+            {
+                if (value.Equals(element, stringComparison))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+    }
+}