addressing a few nits

3 files changed, 24 insertions, 0 deletions

diff --git a/src/csharp/Grpc.Core.Tests/MetadataTest.cs b/src/csharp/Grpc.Core.Tests/MetadataTest.cs
index 171c5c470e..d85d7572a6 100644
--- a/src/csharp/Grpc.Core.Tests/MetadataTest.cs
+++ b/src/csharp/Grpc.Core.Tests/MetadataTest.cs
@@ -73,6 +73,23 @@ namespace Grpc.Core.Tests
         }
 
         [Test]
+        public void KeysAreNormalized_UppercaseKey()
+        {
+            var uppercaseKey = "ABC";
+            var entry = new Metadata.Entry(uppercaseKey, "XYZ");
+            Assert.AreEqual("abc", entry.Key);
+        }
+
+        [Test]
+        public void KeysAreNormalized_LowercaseKey()
+        {
+            var lowercaseKey = "abc";
+            var entry = new Metadata.Entry(lowercaseKey, "XYZ");
+            // no allocation if key already lowercase
+            Assert.AreSame(lowercaseKey, entry.Key);
+        }
+
+        [Test]
         public void Entry_ConstructionPreconditions()
         {
             Assert.Throws(typeof(ArgumentNullException), () => new Metadata.Entry(null, "xyz"));
diff --git a/src/csharp/Grpc.Core/Internal/MarshalUtils.cs b/src/csharp/Grpc.Core/Internal/MarshalUtils.cs
index 73b7a2ef95..09ded1a036 100644
--- a/src/csharp/Grpc.Core/Internal/MarshalUtils.cs
+++ b/src/csharp/Grpc.Core/Internal/MarshalUtils.cs
@@ -36,8 +36,12 @@ namespace Grpc.Core.Internal
         public static string PtrToStringUTF8(IntPtr ptr, int len)
         {
             if (len == 0)
+            {
                 return "";
+            }
 
+            // TODO(jtattermusch): once Span dependency is added,
+            // use Span-based API to decode the string without copying the buffer.
             var bytes = new byte[len];
             Marshal.Copy(ptr, bytes, 0, len);
             return EncodingUTF8.GetString(bytes);
diff --git a/src/csharp/Grpc.Core/Metadata.cs b/src/csharp/Grpc.Core/Metadata.cs
index 122c1e8883..a9aa2cbbfc 100644
--- a/src/csharp/Grpc.Core/Metadata.cs
+++ b/src/csharp/Grpc.Core/Metadata.cs
@@ -361,7 +361,10 @@ namespace Grpc.Core
                 GrpcPreconditions.CheckArgument(IsValidKey(key, out bool isLowercase), 
                     "Metadata entry key not valid. Keys can only contain lowercase alphanumeric characters, underscores, hyphens and dots.");
                 if (isLowercase)
+                {
+                    // save allocation of a new string if already lowercase
                     return key;
+                }
                 
                 return key.ToLowerInvariant();
             }