1 files changed, 17 insertions, 11 deletions

diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs
index df1292dc..4b0670f6 100644..100755
--- a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs
@@ -33,6 +33,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text;
 
@@ -51,25 +52,30 @@ namespace Google.Protobuf.WellKnownTypes
         /// </remarks>
         /// <param name="paths">Paths in the field mask</param>
         /// <param name="diagnosticOnly">Determines the handling of non-normalized values</param>
-        /// <exception cref="InvalidOperationException">The represented duration is invalid, and <paramref name="diagnosticOnly"/> is <c>false</c>.</exception>
+        /// <exception cref="InvalidOperationException">The represented field mask is invalid, and <paramref name="diagnosticOnly"/> is <c>false</c>.</exception>
         internal static string ToJson(IList<string> paths, bool diagnosticOnly)
         {
             var firstInvalid = paths.FirstOrDefault(p => !ValidatePath(p));
             if (firstInvalid == null)
             {
-                var builder = new StringBuilder();
-                JsonFormatter.WriteString(builder, string.Join(",", paths.Select(JsonFormatter.ToCamelCase)));
-                return builder.ToString();
+                var writer = new StringWriter();
+#if NET35
+                var query = paths.Select(JsonFormatter.ToJsonName);
+                JsonFormatter.WriteString(writer, string.Join(",", query.ToArray()));
+#else
+                JsonFormatter.WriteString(writer, string.Join(",", paths.Select(JsonFormatter.ToJsonName)));
+#endif
+                return writer.ToString();
             }
             else
             {
                 if (diagnosticOnly)
                 {
-                    var builder = new StringBuilder();
-                    builder.Append("{ \"@warning\": \"Invalid FieldMask\", \"paths\": ");
-                    JsonFormatter.Default.WriteList(builder, (IList) paths);
-                    builder.Append(" }");
-                    return builder.ToString();
+                    var writer = new StringWriter();
+                    writer.Write("{ \"@warning\": \"Invalid FieldMask\", \"paths\": ");
+                    JsonFormatter.Default.WriteList(writer, (IList)paths);
+                    writer.Write(" }");
+                    return writer.ToString();
                 }
                 else
                 {
@@ -79,9 +85,9 @@ namespace Google.Protobuf.WellKnownTypes
         }
 
         /// <summary>
-        /// Camel-case converter with added strictness for field mask formatting.
+        /// Checks whether the given path is valid for a field mask.
         /// </summary>
-        /// <exception cref="InvalidOperationException">The field mask is invalid for JSON representation</exception>
+        /// <returns>true if the path is valid; false otherwise</returns>
         private static bool ValidatePath(string input)
         {
             for (int i = 0; i < input.Length; i++)