Cherrypick for csharp, including:

Add preserve UnknownFields
Compare floating point values bitwise
Add auto-generated header to C# generated files

1 files changed, 3 insertions, 1 deletions

diff --git a/csharp/src/Google.Protobuf/FieldCodec.cs b/csharp/src/Google.Protobuf/FieldCodec.cs
index c28b47e1..a11f2420 100644
--- a/csharp/src/Google.Protobuf/FieldCodec.cs
+++ b/csharp/src/Google.Protobuf/FieldCodec.cs
@@ -30,6 +30,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endregion
 
+using Google.Protobuf.Collections;
 using Google.Protobuf.Compatibility;
 using Google.Protobuf.WellKnownTypes;
 using System;
@@ -346,6 +347,7 @@ namespace Google.Protobuf
     /// </remarks>
     public sealed class FieldCodec<T>
     {
+        private static readonly EqualityComparer<T> EqualityComparer = ProtobufEqualityComparers.GetEqualityComparer<T>();
         private static readonly T DefaultDefault;
         // Only non-nullable value types support packing. This is the simplest way of detecting that.
         private static readonly bool TypeSupportsPacking = default(T) != null;
@@ -469,6 +471,6 @@ namespace Google.Protobuf
         /// </summary>
         public int CalculateSizeWithTag(T value) => IsDefault(value) ? 0 : ValueSizeCalculator(value) + tagSize;
 
-        private bool IsDefault(T value) => EqualityComparer<T>.Default.Equals(value, DefaultValue);
+        private bool IsDefault(T value) => EqualityComparer.Equals(value, DefaultValue);
     }
 }