More tests, and implementation of UninitializedMessageException description.

6 files changed, 128 insertions, 72 deletions

diff --git a/csharp/ProtocolBuffers/AbstractBuilder.cs b/csharp/ProtocolBuffers/AbstractBuilder.cs
index d65c0911..94077d4f 100644
--- a/csharp/ProtocolBuffers/AbstractBuilder.cs
+++ b/csharp/ProtocolBuffers/AbstractBuilder.cs
@@ -12,7 +12,7 @@ namespace Google.ProtocolBuffers {
   /// </summary>
   public abstract class AbstractBuilder : IBuilder {
     #region Unimplemented members of IBuilder
-    public abstract bool Initialized { get; }
+    public abstract bool IsInitialized { get; }
     public abstract IDictionary<FieldDescriptor, object> AllFields { get; }
     public abstract object this[FieldDescriptor field] { get; set; }
     public abstract MessageDescriptor DescriptorForType { get; }
@@ -78,7 +78,7 @@ namespace Google.ProtocolBuffers {
       //   implementations).
       // TODO(jonskeet):  Provide a function somewhere called makeDeepCopy()
       //   which allows people to make secure deep copies of messages.
-      foreach (KeyValuePair<FieldDescriptor, object> entry in AllFields) {
+      foreach (KeyValuePair<FieldDescriptor, object> entry in other.AllFields) {
         FieldDescriptor field = entry.Key;
         if (field.IsRepeated) {
           // Concatenate repeated fields
diff --git a/csharp/ProtocolBuffers/DescriptorProtos/DescriptorProtoFile.cs b/csharp/ProtocolBuffers/DescriptorProtos/DescriptorProtoFile.cs
index 14e1f177..a7772cf8 100644
--- a/csharp/ProtocolBuffers/DescriptorProtos/DescriptorProtoFile.cs
+++ b/csharp/ProtocolBuffers/DescriptorProtos/DescriptorProtoFile.cs
@@ -278,9 +278,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   
   #region Messages
   public sealed partial class FileDescriptorProto : pb::GeneratedMessage<FileDescriptorProto, FileDescriptorProto.Builder> {
-    // Use FileDescriptorProto.CreateBuilder() to construct.
-    private FileDescriptorProto() {}
-    
     private static readonly FileDescriptorProto defaultInstance = new FileDescriptorProto();
     public static FileDescriptorProto DefaultInstance {
       get { return defaultInstance; }
@@ -471,7 +468,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::FileDescriptorProto ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::FileDescriptorProto parseFrom(byte[] data,
+    public static self::FileDescriptorProto ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -960,9 +957,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class DescriptorProto : pb::GeneratedMessage<DescriptorProto, DescriptorProto.Builder> {
-    // Use DescriptorProto.CreateBuilder() to construct.
-    private DescriptorProto() {}
-    
     private static readonly DescriptorProto defaultInstance = new DescriptorProto();
     public static DescriptorProto DefaultInstance {
       get { return defaultInstance; }
@@ -983,9 +977,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     #region Nested types
     public static class Types {
       public sealed partial class ExtensionRange : pb::GeneratedMessage<ExtensionRange, ExtensionRange.Builder> {
-        // Use ExtensionRange.CreateBuilder() to construct.
-        private ExtensionRange() {}
-        
         private static readonly ExtensionRange defaultInstance = new ExtensionRange();
         public static ExtensionRange DefaultInstance {
           get { return defaultInstance; }
@@ -1069,7 +1060,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
         public static self::DescriptorProto.Types.ExtensionRange ParseFrom(byte[] data) {
           return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
         }
-        public static self::DescriptorProto.Types.ExtensionRange parseFrom(byte[] data,
+        public static self::DescriptorProto.Types.ExtensionRange ParseFrom(byte[] data,
             pb::ExtensionRegistry extensionRegistry) {
           return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                    .BuildParsed();
@@ -1389,7 +1380,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::DescriptorProto ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::DescriptorProto parseFrom(byte[] data,
+    public static self::DescriptorProto ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -1867,9 +1858,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class FieldDescriptorProto : pb::GeneratedMessage<FieldDescriptorProto, FieldDescriptorProto.Builder> {
-    // Use FieldDescriptorProto.CreateBuilder() to construct.
-    private FieldDescriptorProto() {}
-    
     private static readonly FieldDescriptorProto defaultInstance = new FieldDescriptorProto();
     public static FieldDescriptorProto DefaultInstance {
       get { return defaultInstance; }
@@ -2079,7 +2067,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::FieldDescriptorProto ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::FieldDescriptorProto parseFrom(byte[] data,
+    public static self::FieldDescriptorProto ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -2428,9 +2416,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class EnumDescriptorProto : pb::GeneratedMessage<EnumDescriptorProto, EnumDescriptorProto.Builder> {
-    // Use EnumDescriptorProto.CreateBuilder() to construct.
-    private EnumDescriptorProto() {}
-    
     private static readonly EnumDescriptorProto defaultInstance = new EnumDescriptorProto();
     public static EnumDescriptorProto DefaultInstance {
       get { return defaultInstance; }
@@ -2532,7 +2517,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::EnumDescriptorProto ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::EnumDescriptorProto parseFrom(byte[] data,
+    public static self::EnumDescriptorProto ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -2774,9 +2759,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class EnumValueDescriptorProto : pb::GeneratedMessage<EnumValueDescriptorProto, EnumValueDescriptorProto.Builder> {
-    // Use EnumValueDescriptorProto.CreateBuilder() to construct.
-    private EnumValueDescriptorProto() {}
-    
     private static readonly EnumValueDescriptorProto defaultInstance = new EnumValueDescriptorProto();
     public static EnumValueDescriptorProto DefaultInstance {
       get { return defaultInstance; }
@@ -2876,7 +2858,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::EnumValueDescriptorProto ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::EnumValueDescriptorProto parseFrom(byte[] data,
+    public static self::EnumValueDescriptorProto ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -3085,9 +3067,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class ServiceDescriptorProto : pb::GeneratedMessage<ServiceDescriptorProto, ServiceDescriptorProto.Builder> {
-    // Use ServiceDescriptorProto.CreateBuilder() to construct.
-    private ServiceDescriptorProto() {}
-    
     private static readonly ServiceDescriptorProto defaultInstance = new ServiceDescriptorProto();
     public static ServiceDescriptorProto DefaultInstance {
       get { return defaultInstance; }
@@ -3189,7 +3168,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::ServiceDescriptorProto ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::ServiceDescriptorProto parseFrom(byte[] data,
+    public static self::ServiceDescriptorProto ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -3431,9 +3410,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class MethodDescriptorProto : pb::GeneratedMessage<MethodDescriptorProto, MethodDescriptorProto.Builder> {
-    // Use MethodDescriptorProto.CreateBuilder() to construct.
-    private MethodDescriptorProto() {}
-    
     private static readonly MethodDescriptorProto defaultInstance = new MethodDescriptorProto();
     public static MethodDescriptorProto DefaultInstance {
       get { return defaultInstance; }
@@ -3549,7 +3525,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::MethodDescriptorProto ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::MethodDescriptorProto parseFrom(byte[] data,
+    public static self::MethodDescriptorProto ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -3784,9 +3760,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class FileOptions : pb::GeneratedMessage<FileOptions, FileOptions.Builder> {
-    // Use FileOptions.CreateBuilder() to construct.
-    private FileOptions() {}
-    
     private static readonly FileOptions defaultInstance = new FileOptions();
     public static FileOptions DefaultInstance {
       get { return defaultInstance; }
@@ -3991,7 +3964,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::FileOptions ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::FileOptions parseFrom(byte[] data,
+    public static self::FileOptions ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -4340,9 +4313,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class MessageOptions : pb::GeneratedMessage<MessageOptions, MessageOptions.Builder> {
-    // Use MessageOptions.CreateBuilder() to construct.
-    private MessageOptions() {}
-    
     private static readonly MessageOptions defaultInstance = new MessageOptions();
     public static MessageOptions DefaultInstance {
       get { return defaultInstance; }
@@ -4410,7 +4380,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::MessageOptions ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::MessageOptions parseFrom(byte[] data,
+    public static self::MessageOptions ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -4546,9 +4516,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class FieldOptions : pb::GeneratedMessage<FieldOptions, FieldOptions.Builder> {
-    // Use FieldOptions.CreateBuilder() to construct.
-    private FieldOptions() {}
-    
     private static readonly FieldOptions defaultInstance = new FieldOptions();
     public static FieldOptions DefaultInstance {
       get { return defaultInstance; }
@@ -4641,7 +4608,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::FieldOptions ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::FieldOptions parseFrom(byte[] data,
+    public static self::FieldOptions ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -4808,9 +4775,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class EnumOptions : pb::GeneratedMessage<EnumOptions, EnumOptions.Builder> {
-    // Use EnumOptions.CreateBuilder() to construct.
-    private EnumOptions() {}
-    
     private static readonly EnumOptions defaultInstance = new EnumOptions();
     public static EnumOptions DefaultInstance {
       get { return defaultInstance; }
@@ -4862,7 +4826,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::EnumOptions ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::EnumOptions parseFrom(byte[] data,
+    public static self::EnumOptions ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -4972,9 +4936,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class EnumValueOptions : pb::GeneratedMessage<EnumValueOptions, EnumValueOptions.Builder> {
-    // Use EnumValueOptions.CreateBuilder() to construct.
-    private EnumValueOptions() {}
-    
     private static readonly EnumValueOptions defaultInstance = new EnumValueOptions();
     public static EnumValueOptions DefaultInstance {
       get { return defaultInstance; }
@@ -5026,7 +4987,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::EnumValueOptions ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::EnumValueOptions parseFrom(byte[] data,
+    public static self::EnumValueOptions ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -5136,9 +5097,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class ServiceOptions : pb::GeneratedMessage<ServiceOptions, ServiceOptions.Builder> {
-    // Use ServiceOptions.CreateBuilder() to construct.
-    private ServiceOptions() {}
-    
     private static readonly ServiceOptions defaultInstance = new ServiceOptions();
     public static ServiceOptions DefaultInstance {
       get { return defaultInstance; }
@@ -5190,7 +5148,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::ServiceOptions ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::ServiceOptions parseFrom(byte[] data,
+    public static self::ServiceOptions ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
@@ -5300,9 +5258,6 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
   }
   
   public sealed partial class MethodOptions : pb::GeneratedMessage<MethodOptions, MethodOptions.Builder> {
-    // Use MethodOptions.CreateBuilder() to construct.
-    private MethodOptions() {}
-    
     private static readonly MethodOptions defaultInstance = new MethodOptions();
     public static MethodOptions DefaultInstance {
       get { return defaultInstance; }
@@ -5354,7 +5309,7 @@ namespace Google.ProtocolBuffers.DescriptorProtos {
     public static self::MethodOptions ParseFrom(byte[] data) {
       return ((Builder) CreateBuilder().MergeFrom(data)).BuildParsed();
     }
-    public static self::MethodOptions parseFrom(byte[] data,
+    public static self::MethodOptions ParseFrom(byte[] data,
         pb::ExtensionRegistry extensionRegistry) {
       return ((Builder) CreateBuilder().MergeFrom(data, extensionRegistry))
                .BuildParsed();
diff --git a/csharp/ProtocolBuffers/DynamicMessage.cs b/csharp/ProtocolBuffers/DynamicMessage.cs
index 5ffbdfbb..675c4c18 100644
--- a/csharp/ProtocolBuffers/DynamicMessage.cs
+++ b/csharp/ProtocolBuffers/DynamicMessage.cs
@@ -5,6 +5,11 @@ using System.Text;
 using Google.ProtocolBuffers.Descriptors;
 
 namespace Google.ProtocolBuffers {
+
+  /// <summary>
+  /// An implementation of IMessage that can represent arbitrary types, given a MessageaDescriptor.
+  /// TODO: Implement appropriate generics.
+  /// </summary>
   public class DynamicMessage : AbstractMessage {
 
     private readonly MessageDescriptor type;
@@ -242,7 +247,7 @@ namespace Google.ProtocolBuffers {
         return this;
       }
 
-      public override IBuilder  MergeFrom(IMessage other) {
+      public override IBuilder MergeFrom(IMessage other) {
         if (other.DescriptorForType != type) {
           throw new ArgumentException("MergeFrom(IMessage) can only merge messages of the same type.");
         }
@@ -251,7 +256,7 @@ namespace Google.ProtocolBuffers {
       }
 
       protected override IMessage BuildImpl() {
-   	    if (!Initialized) {
+   	    if (!IsInitialized) {
           throw new UninitializedMessageException(new DynamicMessage(type, fields, unknownFields));
         }
         return BuildPartialImpl();
@@ -263,7 +268,7 @@ namespace Google.ProtocolBuffers {
       /// </summary>
       /// <returns></returns>
       internal DynamicMessage BuildParsed() {
-        if (!Initialized) {
+        if (!IsInitialized) {
           throw new UninitializedMessageException(new DynamicMessage(type, fields, unknownFields)).AsInvalidProtocolBufferException();
         }
         return (DynamicMessage) BuildPartialImpl();
@@ -283,7 +288,7 @@ namespace Google.ProtocolBuffers {
         return result;
       }
 
-      public override bool Initialized {
+      public override bool IsInitialized {
       	get { return fields.IsInitializedWithRespectTo(type); }
       }
 
diff --git a/csharp/ProtocolBuffers/GeneratedBuilder.cs b/csharp/ProtocolBuffers/GeneratedBuilder.cs
index 154aa05f..a4114b5d 100644
--- a/csharp/ProtocolBuffers/GeneratedBuilder.cs
+++ b/csharp/ProtocolBuffers/GeneratedBuilder.cs
@@ -26,7 +26,7 @@ namespace Google.ProtocolBuffers {
       get { return MessageBeingBuilt.FieldAccesseorsFromBuilder; }
     }
 
-    public override bool Initialized {
+    public override bool IsInitialized {
       get { return MessageBeingBuilt.IsInitialized; }
     }
 
@@ -212,7 +212,7 @@ namespace Google.ProtocolBuffers {
     /// TODO(jonskeet): This used to be generated for each class. Find out why.
     /// </summary>
     public TMessage BuildParsed() {
-      if (!Initialized) {
+      if (!IsInitialized) {
         throw new UninitializedMessageException(MessageBeingBuilt).AsInvalidProtocolBufferException();
       }
       return BuildPartial();
@@ -223,7 +223,7 @@ namespace Google.ProtocolBuffers {
     /// TODO(jonskeet): This used to be generated for each class. Find out why.
     /// </summary>
     public TMessage Build() {
-      if (!Initialized) {
+      if (!IsInitialized) {
         throw new UninitializedMessageException(MessageBeingBuilt);
       }
       return BuildPartial();
diff --git a/csharp/ProtocolBuffers/IBuilder.cs b/csharp/ProtocolBuffers/IBuilder.cs
index b46842cd..dcb3d272 100644
--- a/csharp/ProtocolBuffers/IBuilder.cs
+++ b/csharp/ProtocolBuffers/IBuilder.cs
@@ -33,7 +33,7 @@ namespace Google.ProtocolBuffers {
     /// Returns true iff all required fields in the message and all
     /// embedded messages are set.
     /// </summary>
-    bool Initialized { get; }
+    bool IsInitialized { get; }
 
     /// <summary>
     /// Behaves like the equivalent property in IMessage&lt;T&gt;.
@@ -172,7 +172,7 @@ namespace Google.ProtocolBuffers {
     /// required fields, it will throw an UninitializedMessageException.
     /// There are a few good ways to deal with this:
     /// <list>
-    /// <item>Call Initialized to verify to verify that all required fields are
+    /// <item>Call IsInitialized to verify to verify that all required fields are
     /// set before building.</item>
     /// <item>Parse  the message separately using one of the static ParseFrom
     /// methods, then use MergeFrom(IMessage&lt;T&gt;) to merge it with
diff --git a/csharp/ProtocolBuffers/UninitializedMessageException.cs b/csharp/ProtocolBuffers/UninitializedMessageException.cs
index 530f2057..01cdd2f1 100644
--- a/csharp/ProtocolBuffers/UninitializedMessageException.cs
+++ b/csharp/ProtocolBuffers/UninitializedMessageException.cs
@@ -14,15 +14,111 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Text;
+using Google.ProtocolBuffers.Collections;
+using Google.ProtocolBuffers.Descriptors;
 
 namespace Google.ProtocolBuffers {
   public class UninitializedMessageException : Exception {
 
-    public UninitializedMessageException(IMessage message) {
+    private readonly IList<string> missingFields;
+
+    public UninitializedMessageException(IMessage message)
+        : this(FindMissingFields(message)) {
+    }
+
+    private UninitializedMessageException(IList<string> missingFields)
+        : base(BuildDescription(missingFields)) {
+      this.missingFields = Lists.AsReadOnly(missingFields);
     }
 
+
+    /// <summary>
+    /// Converts this exception into an InvalidProtocolBufferException.
+    /// When a parsed message is missing required fields, this should be thrown
+    /// instead of UninitializedMessageException.
+    /// </summary>
     public InvalidProtocolBufferException AsInvalidProtocolBufferException() {
       return new InvalidProtocolBufferException(Message);
     }
+
+    /// <summary>
+    /// Constructs the description string for a given list of missing fields.
+    /// </summary>
+    private static string BuildDescription(IEnumerable<string> missingFields) {
+      StringBuilder description = new StringBuilder("Message missing required fields: ");
+      bool first = true;
+      foreach(string field in missingFields) {
+        if (first) {
+          first = false;
+        } else {
+          description.Append(", ");
+        }
+        description.Append(field);
+      }
+      return description.ToString();
+    }
+
+    /// <summary>
+    /// Returns a list of the full "paths" of missing required
+    /// fields in the specified message.
+    /// </summary>
+    private static IList<String> FindMissingFields(IMessage message) {
+      List<String> results = new List<String>();
+      FindMissingFields(message, "", results);
+      return results;
+    }
+
+    /// <summary>
+    /// Recursive helper implementing FindMissingFields.
+    /// </summary>
+    private static void FindMissingFields(IMessage message, String prefix, List<String> results) {
+      foreach (FieldDescriptor field in message.DescriptorForType.Fields) {
+        if (field.IsRequired && !message.HasField(field)) {
+          results.Add(prefix + field.Name);
+        }
+      }
+
+      foreach (KeyValuePair<FieldDescriptor, object> entry in message.AllFields) {
+        FieldDescriptor field = entry.Key;
+        object value = entry.Value;
+
+        if (field.MappedType == MappedType.Message) {
+          if (field.IsRepeated) {
+            int i = 0;
+            foreach (object element in (IEnumerable) value) {
+              FindMissingFields((IMessage) element, SubMessagePrefix(prefix, field, i++), results);
+            }
+          } else {
+            if (message.HasField(field)) {
+              FindMissingFields((IMessage) value, SubMessagePrefix(prefix, field, -1), results);
+            }
+          }
+        }
+      }
+    }
+
+    private static String SubMessagePrefix(String prefix, FieldDescriptor field, int index) {
+      StringBuilder result = new StringBuilder(prefix);
+      if (field.IsExtension) {
+        result.Append('(')
+              .Append(field.FullName)
+              .Append(')');
+      } else {
+        result.Append(field.Name);
+      }
+      if (index != -1) {
+        result.Append('[')
+              .Append(index)
+              .Append(']');
+      }
+      result.Append('.');
+      return result.ToString();
+    }
   }
 }
+
+  
+