[SL.Core] Obsolete HashHelpers

src/SixLabors.Core/Helpers/HashHelpers.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
+
 namespace SixLabors
 {
     /// <summary>
@@ -14,6 +16,7 @@ namespace SixLabors
         /// <param name="h1">Hash code one</param>
         /// <param name="h2">Hash code two</param>
         /// <returns>Returns a hash code for the provided hash codes.</returns>
+        [Obsolete("Use HashCode.Combine instead")]
         public static int Combine(int h1, int h2)
         {
             // Lifted from coreFX repo
@@ -33,6 +36,7 @@ namespace SixLabors
         /// <param name="h2">Hash code two</param>
         /// <param name="h3">Hash code three</param>
         /// <returns>Returns a hash code for the provided hash codes.</returns>
+        [Obsolete("Use HashCode.Combine instead")]
         public static int Combine(int h1, int h2, int h3)
         {
             int hash = Combine(h1, h2);
@@ -50,6 +54,7 @@ namespace SixLabors
         /// <param name="h3">Hash code three</param>
         /// <param name="h4">Hash code four</param>
         /// <returns>Returns a hash code for the provided hash codes.</returns>
+        [Obsolete("Use HashCode.Combine instead")]
         public static int Combine(int h1, int h2, int h3, int h4)
         {
             int hash = Combine(h1, h2);