Minor cleanup.

- Make some members internal
- Remove a lot of FrameworkPortability that isn't required
- Start adding documentation comments
- Remove some more group-based members
- Not passing in "the last tag read" into Read*Array, g

csharp/src/AddressBook/Addressbook.cs

@@ -214,7 +214,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
             break;
           }
           case 34: {
-            input.ReadMessageArray(tag, phone_, global::Google.ProtocolBuffers.Examples.AddressBook.Person.Types.PhoneNumber.Parser);
+            input.ReadMessageArray(phone_, global::Google.ProtocolBuffers.Examples.AddressBook.Person.Types.PhoneNumber.Parser);
             break;
           }
         }
@@ -432,7 +432,7 @@ namespace Google.ProtocolBuffers.Examples.AddressBook {
             }
             break;
           case 10: {
-            input.ReadMessageArray(tag, person_, global::Google.ProtocolBuffers.Examples.AddressBook.Person.Parser);
+            input.ReadMessageArray(person_, global::Google.ProtocolBuffers.Examples.AddressBook.Person.Parser);
             break;
           }
         }

csharp/src/ProtocolBuffers.Test/CodedInputStreamTest.cs

@@ -489,7 +489,7 @@ namespace Google.Protobuf
             Assert.IsTrue(input.ReadTag(out tag));
 
             RepeatedField<TestNegEnum> values = new RepeatedField<TestNegEnum>();
-            input.ReadEnumArray(tag, values);
+            input.ReadEnumArray(values);
 
             Assert.AreEqual(6, values.Count);
             Assert.AreEqual(TestNegEnum.None, values[0]);
@@ -513,7 +513,7 @@ namespace Google.Protobuf
             Assert.IsTrue(input.ReadTag(out tag));
 
             RepeatedField<TestNegEnum> values = new RepeatedField<TestNegEnum>();
-            input.ReadEnumArray(tag, values);
+            input.ReadEnumArray(values);
 
             Assert.AreEqual(6, values.Count);
             Assert.AreEqual(TestNegEnum.None, values[0]);

csharp/src/ProtocolBuffers.Test/CodedOutputStreamTest.cs

@@ -326,7 +326,7 @@ namespace Google.Protobuf
             Assert.IsTrue(input.ReadTag(out tag));
 
             List<int> values = new List<int>();
-            input.ReadInt32Array(tag, values);
+            input.ReadInt32Array(values);
 
             Assert.AreEqual(6, values.Count);
             for (int i = 0; i > -6; i--)
@@ -349,7 +349,7 @@ namespace Google.Protobuf
             Assert.IsTrue(input.ReadTag(out tag));
 
             List<int> values = new List<int>();
-            input.ReadInt32Array(tag, values);
+            input.ReadInt32Array(values);
 
             Assert.AreEqual(6, values.Count);
             for (int i = 0; i > -6; i--)

csharp/src/ProtocolBuffers.Test/TestProtos/UnittestIssues.cs

@@ -218,12 +218,12 @@ namespace UnitTest.Issues.TestProtos {
           }
           case 18:
           case 16: {
-            input.ReadEnumArray<global::UnitTest.Issues.TestProtos.NegativeEnum>(tag, values_);
+            input.ReadEnumArray<global::UnitTest.Issues.TestProtos.NegativeEnum>(values_);
             break;
           }
           case 26:
           case 24: {
-            input.ReadEnumArray<global::UnitTest.Issues.TestProtos.NegativeEnum>(tag, packedValues_);
+            input.ReadEnumArray<global::UnitTest.Issues.TestProtos.NegativeEnum>(packedValues_);
             break;
           }
         }
@@ -495,7 +495,7 @@ namespace UnitTest.Issues.TestProtos {
           }
           case 18:
           case 16: {
-            input.ReadInt32Array(tag, primitiveArray_);
+            input.ReadInt32Array(primitiveArray_);
             break;
           }
           case 26: {
@@ -506,7 +506,7 @@ namespace UnitTest.Issues.TestProtos {
             break;
           }
           case 34: {
-            input.ReadMessageArray(tag, messageArray_, global::UnitTest.Issues.TestProtos.DeprecatedChild.Parser);
+            input.ReadMessageArray(messageArray_, global::UnitTest.Issues.TestProtos.DeprecatedChild.Parser);
             break;
           }
           case 40: {
@@ -515,7 +515,7 @@ namespace UnitTest.Issues.TestProtos {
           }
           case 50:
           case 48: {
-            input.ReadEnumArray<global::UnitTest.Issues.TestProtos.DeprecatedEnum>(tag, enumArray_);
+            input.ReadEnumArray<global::UnitTest.Issues.TestProtos.DeprecatedEnum>(enumArray_);
             break;
           }
         }

csharp/src/ProtocolBuffers/ByteArray.cs

@@ -51,7 +51,7 @@ namespace Google.Protobuf
         /// <summary>
         /// Determines which copy routine to use based on the number of bytes to be copied.
         /// </summary>
-        public static void Copy(byte[] src, int srcOffset, byte[] dst, int dstOffset, int count)
+        internal static void Copy(byte[] src, int srcOffset, byte[] dst, int dstOffset, int count)
         {
             if (count > CopyThreshold)
             {
@@ -66,7 +66,7 @@ namespace Google.Protobuf
         /// <summary>
         /// Copy the bytes provided with a for loop, faster when there are only a few bytes to copy
         /// </summary>
-        public static void ByteCopy(byte[] src, int srcOffset, byte[] dst, int dstOffset, int count)
+        internal static void ByteCopy(byte[] src, int srcOffset, byte[] dst, int dstOffset, int count)
         {
             int stop = srcOffset + count;
             for (int i = srcOffset; i < stop; i++)
@@ -78,12 +78,11 @@ namespace Google.Protobuf
         /// <summary>
         /// Reverses the order of bytes in the array
         /// </summary>
-        public static void Reverse(byte[] bytes)
+        internal static void Reverse(byte[] bytes)
         {
-            byte temp;
             for (int first = 0, last = bytes.Length - 1; first < last; first++, last--)
             {
-                temp = bytes[first];
+                byte temp = bytes[first];
                 bytes[first] = bytes[last];
                 bytes[last] = temp;
             }

csharp/src/ProtocolBuffers/CodedInputStream.cs

@@ -37,9 +37,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Text;
 using Google.Protobuf.Collections;
-using Google.Protobuf.Descriptors;
 
 namespace Google.Protobuf
 {
@@ -183,7 +181,7 @@ namespace Google.Protobuf
         /// </summary>
         /// <exception cref="InvalidProtocolBufferException">The last
         /// tag read was not the one specified</exception>
-        public void CheckLastTagWas(uint value)
+        internal void CheckLastTagWas(uint value)
         {
             if (lastTag != value)
             {
@@ -251,7 +249,7 @@ namespace Google.Protobuf
         /// </summary>
         public double ReadDouble()
         {
-            return FrameworkPortability.Int64ToDouble((long) ReadRawLittleEndian64());
+            return BitConverter.Int64BitsToDouble((long) ReadRawLittleEndian64());
         }
 
         /// <summary>
@@ -347,21 +345,6 @@ namespace Google.Protobuf
             return CodedOutputStream.Utf8Encoding.GetString(ReadRawBytes(size), 0, size);
         }
 
-        /// <summary>
-        /// Reads a group field value from the stream.
-        /// </summary>    
-        public void ReadGroup(int fieldNumber, IMessage message)
-        {
-            if (recursionDepth >= recursionLimit)
-            {
-                throw InvalidProtocolBufferException.RecursionLimitExceeded();
-            }
-            ++recursionDepth;
-            message.MergeFrom(this);
-            CheckLastTagWas(WireFormat.MakeTag(fieldNumber, WireFormat.WireType.EndGroup));
-            --recursionDepth;
-        }
-
         /// <summary>
         /// Reads an embedded message field value from the stream.
         /// </summary>   
@@ -516,24 +499,34 @@ namespace Google.Protobuf
             return false;
         }
 
-        public void ReadStringArray(uint fieldTag, ICollection<string> list)
+        /// <summary>
+        /// Reads a string array.
+        /// </summary>
+        /// <remarks>The stream is assumed to be positioned after a tag indicating the field
+        /// repeated string value. A string is read, and then if the next tag is the same,
+        /// the process is repeated, until the next tag is a different one.</remarks>
+        /// <param name="list"></param>
+        public void ReadStringArray(ICollection<string> list)
         {
+            uint fieldTag = lastTag;
             do
             {
                 list.Add(ReadString());
             } while (ContinueArray(fieldTag));
         }
 
-        public void ReadBytesArray(uint fieldTag, ICollection<ByteString> list)
+        public void ReadBytesArray(ICollection<ByteString> list)
         {
+            uint fieldTag = lastTag;
             do
             {
                 list.Add(ReadBytes());
             } while (ContinueArray(fieldTag));
         }
 
-        public void ReadBoolArray(uint fieldTag, ICollection<bool> list)
+        public void ReadBoolArray(ICollection<bool> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -545,8 +538,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadInt32Array(uint fieldTag, ICollection<int> list)
+        public void ReadInt32Array(ICollection<int> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -558,8 +552,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadSInt32Array(uint fieldTag, ICollection<int> list)
+        public void ReadSInt32Array(ICollection<int> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -571,8 +566,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadUInt32Array(uint fieldTag, ICollection<uint> list)
+        public void ReadUInt32Array(ICollection<uint> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -584,8 +580,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadFixed32Array(uint fieldTag, ICollection<uint> list)
+        public void ReadFixed32Array(ICollection<uint> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -597,8 +594,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadSFixed32Array(uint fieldTag, ICollection<int> list)
+        public void ReadSFixed32Array(ICollection<int> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -610,8 +608,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadInt64Array(uint fieldTag, ICollection<long> list)
+        public void ReadInt64Array(ICollection<long> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -623,8 +622,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadSInt64Array(uint fieldTag, ICollection<long> list)
+        public void ReadSInt64Array(ICollection<long> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -636,8 +636,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadUInt64Array(uint fieldTag, ICollection<ulong> list)
+        public void ReadUInt64Array(ICollection<ulong> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -649,8 +650,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadFixed64Array(uint fieldTag, ICollection<ulong> list)
+        public void ReadFixed64Array(ICollection<ulong> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -662,8 +664,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadSFixed64Array(uint fieldTag, ICollection<long> list)
+        public void ReadSFixed64Array(ICollection<long> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -675,8 +678,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadDoubleArray(uint fieldTag, ICollection<double> list)
+        public void ReadDoubleArray(ICollection<double> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -688,8 +692,9 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadFloatArray(uint fieldTag, ICollection<float> list)
+        public void ReadFloatArray(ICollection<float> list)
         {
+            uint fieldTag = lastTag;
             bool isPacked;
             int holdLimit;
             if (BeginArray(fieldTag, out isPacked, out holdLimit))
@@ -701,9 +706,10 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadEnumArray<T>(uint fieldTag, RepeatedField<T> list)
+        public void ReadEnumArray<T>(RepeatedField<T> list)
             where T : struct, IComparable, IFormattable
         {
+            uint fieldTag = lastTag;
             WireFormat.WireType wformat = WireFormat.GetTagWireType(fieldTag);
 
             // 2.3 allows packed form even if the field is not declared packed.
@@ -727,9 +733,10 @@ namespace Google.Protobuf
             }
         }
 
-        public void ReadMessageArray<T>(uint fieldTag, ICollection<T> list, MessageParser<T> messageParser)
+        public void ReadMessageArray<T>(ICollection<T> list, MessageParser<T> messageParser)
             where T : IMessage<T>
         {
+            uint fieldTag = lastTag;
             do
             {
                 T message = messageParser.CreateTemplate();
@@ -737,17 +744,6 @@ namespace Google.Protobuf
                 list.Add(message);
             } while (ContinueArray(fieldTag));
         }
-
-        public void ReadGroupArray<T>(uint fieldTag, ICollection<T> list, MessageParser<T> messageParser)
-            where T : IMessage<T>
-        {
-            do
-            {
-                T message = messageParser.CreateTemplate();
-                ReadGroup(WireFormat.GetTagFieldNumber(fieldTag), message);
-                list.Add(message);
-            } while (ContinueArray(fieldTag));
-        }
         #endregion
 
         #region Underlying reading primitives

csharp/src/ProtocolBuffers/CodedOutputStream.cs

@@ -35,12 +35,9 @@
 #endregion
 
 using System;
-using System.Collections;
 using System.IO;
-using System.Linq;
 using System.Text;
 using Google.Protobuf.Collections;
-using Google.Protobuf.Descriptors;
 
 namespace Google.Protobuf
 {
@@ -151,7 +148,7 @@ namespace Google.Protobuf
         /// </summary>
         public void WriteDouble(double value)
         {
-            WriteRawLittleEndian64((ulong)FrameworkPortability.DoubleToInt64(value));
+            WriteRawLittleEndian64((ulong)BitConverter.DoubleToInt64Bits(value));
         }
 
         /// <summary>

csharp/src/ProtocolBuffers/FrameworkPortability.cs

@@ -35,8 +35,6 @@
 #endregion
 
 using System;
-using System.Globalization;
-using System.Reflection;
 using System.Text.RegularExpressions;
 
 namespace Google.Protobuf
@@ -46,66 +44,10 @@ namespace Google.Protobuf
     /// </summary>
     internal static class FrameworkPortability
     {
-#if COMPACT_FRAMEWORK
-        internal const string NewLine = "\n";
-#else
-        internal static readonly string NewLine = System.Environment.NewLine;
-#endif
-
-#if CLIENTPROFILE
-        internal const RegexOptions CompiledRegexWhereAvailable = RegexOptions.Compiled;
-#else
-        internal const RegexOptions CompiledRegexWhereAvailable = RegexOptions.None;
-#endif
-
-        internal static CultureInfo InvariantCulture 
-        { 
-            get { return CultureInfo.InvariantCulture; } 
-        }
-
-        internal static double Int64ToDouble(long value)
-        {
-#if CLIENTPROFILE
-            return BitConverter.Int64BitsToDouble(value);
-#else
-            double[] arresult = new double[1];
-            Buffer.BlockCopy(new[] { value }, 0, arresult, 0, 8);
-            return arresult[0];
-#endif
-        }
-
-        internal static long DoubleToInt64(double value)
-        {
-#if CLIENTPROFILE
-            return BitConverter.DoubleToInt64Bits(value);
-#else
-            long[] arresult = new long[1];
-            Buffer.BlockCopy(new[] { value }, 0, arresult, 0, 8);
-            return arresult[0];
-#endif
-        }
-
-        internal static bool TryParseInt32(string text, out int number)
-        {
-            return TryParseInt32(text, NumberStyles.Any, InvariantCulture, out number);
-        }
-
-        internal static bool TryParseInt32(string text, NumberStyles style, IFormatProvider format, out int number)
-        {
-#if COMPACT_FRAMEWORK
-                try 
-                {
-                    number = int.Parse(text, style, format); 
-                    return true;
-                }
-                catch 
-                {
-                    number = 0;
-                    return false; 
-                }
-#else
-            return int.TryParse(text, style, format, out number);
-#endif
-        }
+        // The value of RegexOptions.Compiled is 8. We can test for the presence at
+        // execution time using Enum.IsDefined, so a single build will do the right thing
+        // on each platform.
+        internal static readonly RegexOptions CompiledRegexWhereAvailable =
+            Enum.IsDefined(typeof(RegexOptions), 8) ? (RegexOptions)8 : RegexOptions.None;
     }
 }
\ No newline at end of file

csharp/src/ProtocolBuffers/IMessage.cs

@@ -34,30 +34,63 @@
 
 #endregion
 
-using System;
-using System.Collections.Generic;
-using System.IO;
-using Google.Protobuf.Descriptors;
 using Google.Protobuf.FieldAccess;
 
 namespace Google.Protobuf
 {
 
-    // TODO(jonskeet): Do we want a "weak" version of IReflectedMessage?
+    // TODO(jonskeet): Do we want a "weak" (non-generic) version of IReflectedMessage?
+
+    /// <summary>
+    /// Reflection support for a specific message type. message
+    /// </summary>
+    /// <typeparam name="T">The message type being reflected.</typeparam>
     public interface IReflectedMessage<T> where T : IMessage<T>
     {
         FieldAccessorTable<T> Fields { get; }
+        // TODO(jonskeet): Descriptor? Or a single property which has "all you need for reflection"?
     }
 
+    /// <summary>
+    /// Interface for a Protocol Buffers message, supporting
+    /// basic operations required for serialization.
+    /// </summary>
     public interface IMessage
     {
+        /// <summary>
+        /// Merges the data from the specified coded input stream with the current message.
+        /// </summary>
+        /// <remarks>See the user guide for precise merge semantics.</remarks>
+        /// <param name="input"></param>
         void MergeFrom(CodedInputStream input);
+
+        /// <summary>
+        /// Writes the data to the given coded output stream.
+        /// </summary>
+        /// <param name="output">Coded output stream to write the data to. Must not be null.</param>
         void WriteTo(CodedOutputStream output);
+
+        /// <summary>
+        /// Calculates the size of this message in Protocol Buffer wire format, in bytes.
+        /// </summary>
+        /// <returns>The number of bytes required to write this message
+        /// to a coded output stream.</returns>
         int CalculateSize();
     }
 
+    /// <summary>
+    /// Generic interface for a Protocol Buffers message,
+    /// where the type parameter is expected to be the same type as
+    /// the implementation class.
+    /// </summary>
+    /// <typeparam name="T">The message type.</typeparam>
     public interface IMessage<T> : IMessage where T : IMessage<T>
     {
+        /// <summary>
+        /// Merges the given message into this one.
+        /// </summary>
+        /// <remarks>See the user guide for precise merge semantics.</remarks>
+        /// <param name="message">The message to merge with this one. Must not be null.</param>
         void MergeFrom(T message);
     }
 }
\ No newline at end of file

csharp/src/ProtocolBuffers/Extensions.cs → csharp/src/ProtocolBuffers/MessageExtensions.cs

@@ -2,11 +2,15 @@
 
 namespace Google.Protobuf
 {
-    // TODO: MessageExtensions?
-    public static class Extensions
+    /// <summary>
+    /// Extension methods on <see cref="IMessage"/> and <see cref="IMessage{T}"/>.
+    /// </summary>
+    public static class MessageExtensions
     {
         public static void MergeFrom(this IMessage message, byte[] data)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
+            ThrowHelper.ThrowIfNull(data, "data");
             CodedInputStream input = CodedInputStream.CreateInstance(data);
             message.MergeFrom(input);
             input.CheckLastTagWas(0);
@@ -14,6 +18,8 @@ namespace Google.Protobuf
 
         public static void MergeFrom(this IMessage message, ByteString data)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
+            ThrowHelper.ThrowIfNull(data, "data");
             CodedInputStream input = data.CreateCodedInput();
             message.MergeFrom(input);
             input.CheckLastTagWas(0);
@@ -21,6 +27,8 @@ namespace Google.Protobuf
 
         public static void MergeFrom(this IMessage message, Stream input)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
+            ThrowHelper.ThrowIfNull(input, "input");
             CodedInputStream codedInput = CodedInputStream.CreateInstance(input);
             message.MergeFrom(codedInput);
             codedInput.CheckLastTagWas(0);
@@ -28,6 +36,8 @@ namespace Google.Protobuf
 
         public static void MergeDelimitedFrom(this IMessage message, Stream input)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
+            ThrowHelper.ThrowIfNull(input, "input");
             int size = (int)CodedInputStream.ReadRawVarint32(input);
             Stream limitedStream = new LimitedInputStream(input, size);
             message.MergeFrom(limitedStream);
@@ -35,6 +45,7 @@ namespace Google.Protobuf
 
         public static byte[] ToByteArray(this IMessage message)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
             byte[] result = new byte[message.CalculateSize()];
             CodedOutputStream output = CodedOutputStream.CreateInstance(result);
             message.WriteTo(output);
@@ -44,18 +55,17 @@ namespace Google.Protobuf
 
         public static void WriteTo(this IMessage message, Stream output)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
+            ThrowHelper.ThrowIfNull(output, "output");
             CodedOutputStream codedOutput = CodedOutputStream.CreateInstance(output);
             message.WriteTo(codedOutput);
             codedOutput.Flush();
         }
 
-        public static void WriteTo(this IMessage message, CodedOutputStream output)
-        {
-            message.WriteTo(output);
-        }
-
         public static void WriteDelimitedTo(this IMessage message, Stream output)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
+            ThrowHelper.ThrowIfNull(output, "output");
             CodedOutputStream codedOutput = CodedOutputStream.CreateInstance(output);
             codedOutput.WriteRawVarint32((uint)message.CalculateSize());
             message.WriteTo(codedOutput);
@@ -64,6 +74,7 @@ namespace Google.Protobuf
 
         public static ByteString ToByteString(this IMessage message)
         {
+            ThrowHelper.ThrowIfNull(message, "message");
             return ByteString.AttachBytes(message.ToByteArray());
         }        
     }

csharp/src/ProtocolBuffers/MessageParser.cs

 using System;
 using System.IO;
-using Google.Protobuf;
 
 namespace Google.Protobuf
 {
+    /// <summary>
+    /// A parser for a specific message type.
+    /// </summary>
+    /// <remarks>
+    /// <p>
+    /// This delegates most behavior to the
+    /// <see cref="IMessage.MergeFrom"/> implementation within the original type, but
+    /// provides convenient overloads to parse from a variety of sources.
+    /// </p>
+    /// <p>
+    /// Most applications will never need to create their own instances of this type;
+    /// instead, use the static <c>Parser</c> property of a generated message type to obtain a
+    /// parser for that type.
+    /// </p>
+    /// </remarks>
+    /// <typeparam name="T">The type of message to be parsed.</typeparam>
     public sealed class MessageParser<T> where T : IMessage<T>
     {
         private readonly Func<T> factory; 
 
+        /// <summary>
+        /// Creates a new parser.
+        /// </summary>
+        /// <remarks>
+        /// The factory method is effectively an optimization over using a generic constraint
+        /// to require a parameterless constructor: delegates are significantly faster to execute.
+        /// </remarks>
+        /// <param name="factory">Function to invoke when a new, empty message is required.</param>
         public MessageParser(Func<T> factory)
         {
             this.factory = factory;
         }
 
-        // Creates a template instance ready for population.
+        /// <summary>
+        /// Creates a template instance ready for population.
+        /// </summary>
+        /// <returns>An empty message.</returns>
         internal T CreateTemplate()
         {
             return factory();
         }
 
+        /// <summary>
+        /// Parses a message from a byte array.
+        /// </summary>
+        /// <param name="data">The byte array containing the message. Must not be null.</param>
+        /// <returns>The newly parsed message.</returns>
         public T ParseFrom(byte[] data)
         {
+            ThrowHelper.ThrowIfNull(data, "data");
             T message = factory();
             message.MergeFrom(data);
             return message;
@@ -28,6 +60,7 @@ namespace Google.Protobuf
 
         public T ParseFrom(ByteString data)
         {
+            ThrowHelper.ThrowIfNull(data, "data");
             T message = factory();
             message.MergeFrom(data);
             return message;

csharp/src/ProtocolBuffers/ProtocolBuffers.csproj

@@ -84,7 +84,8 @@
     <Compile Include="Descriptors\MethodDescriptor.cs" />
     <Compile Include="Descriptors\PackageDescriptor.cs" />
     <Compile Include="Descriptors\ServiceDescriptor.cs" />
-    <Compile Include="Extensions.cs" />
+    <Compile Include="FrameworkPortability.cs" />
+    <Compile Include="MessageExtensions.cs" />
     <Compile Include="FieldAccess\FieldAccessorBase.cs" />
     <Compile Include="FieldAccess\ReflectionUtil.cs" />
     <Compile Include="FieldAccess\RepeatedFieldAccessor.cs" />
@@ -92,7 +93,6 @@
     <Compile Include="FieldAccess\IFieldAccessor.cs" />
     <Compile Include="FieldAccess\FieldAccessorTable.cs" />
     <Compile Include="FieldAccess\OneofAccessor.cs" />
-    <Compile Include="FrameworkPortability.cs" />
     <Compile Include="IMessage.cs" />
     <Compile Include="InvalidProtocolBufferException.cs" />
     <Compile Include="LimitedInputStream.cs" />

csharp/src/ProtocolBuffers/ThrowHelper.cs

@@ -42,12 +42,12 @@ namespace Google.Protobuf
     /// <summary>
     /// Helper methods for throwing exceptions
     /// </summary>
-    public static class ThrowHelper
+    internal static class ThrowHelper
     {
         /// <summary>
         /// Throws an ArgumentNullException if the given value is null.
         /// </summary>
-        public static void ThrowIfNull(object value, string name)
+        internal static void ThrowIfNull(object value, string name)
         {
             if (value == null)
             {
@@ -58,7 +58,7 @@ namespace Google.Protobuf
         /// <summary>
         /// Throws an ArgumentNullException if the given value is null.
         /// </summary>
-        public static void ThrowIfNull(object value)
+        internal static void ThrowIfNull(object value)
         {
             if (value == null)
             {
@@ -69,7 +69,7 @@ namespace Google.Protobuf
         /// <summary>
         /// Throws an ArgumentNullException if the given value or any element within it is null.
         /// </summary>
-        public static void ThrowIfAnyNull<T>(IEnumerable<T> sequence)
+        internal static void ThrowIfAnyNull<T>(IEnumerable<T> sequence)
         {
             foreach (T t in sequence)
             {
@@ -79,14 +79,5 @@ namespace Google.Protobuf
                 }
             }
         }
-
-        public static Exception CreateMissingMethod(Type type, string methodName)
-        {
-#if CLIENTPROFILE
-            return new System.MissingMethodException(type.FullName, methodName);
-#else
-            return new System.ArgumentException(String.Format("The method '{0}' was not found on type {1}.", methodName, type));
-#endif
-        }
     }
 }
\ No newline at end of file

src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc

@@ -76,7 +76,7 @@ void RepeatedEnumFieldGenerator::GenerateMergingCode(io::Printer* printer) {
 void RepeatedEnumFieldGenerator::GenerateParsingCode(io::Printer* printer) {
   printer->Print(
     variables_,
-    "input.ReadEnumArray<$type_name$>(tag, $name$_);\n");
+    "input.ReadEnumArray<$type_name$>($name$_);\n");
 }
 
 void RepeatedEnumFieldGenerator::GenerateSerializationCode(io::Printer* printer) {

src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc

@@ -75,7 +75,7 @@ void RepeatedMessageFieldGenerator::GenerateMergingCode(io::Printer* printer) {
 void RepeatedMessageFieldGenerator::GenerateParsingCode(io::Printer* printer) {
   printer->Print(
     variables_,
-    "input.ReadMessageArray(tag, $name$_, $type_name$.Parser);\n");
+    "input.ReadMessageArray($name$_, $type_name$.Parser);\n");
 }
 
 void RepeatedMessageFieldGenerator::GenerateSerializationCode(io::Printer* printer) {

src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc

@@ -75,7 +75,7 @@ void RepeatedPrimitiveFieldGenerator::GenerateMergingCode(io::Printer* printer)
 
 void RepeatedPrimitiveFieldGenerator::GenerateParsingCode(io::Printer* printer) {
   printer->Print(variables_,
-    "input.Read$capitalized_type_name$Array(tag, $name$_);\n");
+    "input.Read$capitalized_type_name$Array($name$_);\n");
 }
 
 void RepeatedPrimitiveFieldGenerator::GenerateSerializationCode(