Added copy of existing classes that will be made Lite
diff --git a/src/ProtocolBuffers/IMessageLite.cs b/src/ProtocolBuffers/IMessageLite.cs
new file mode 100644
index 0000000..ec955c6
--- /dev/null
+++ b/src/ProtocolBuffers/IMessageLite.cs
@@ -0,0 +1,236 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://github.com/jskeet/dotnet-protobufs/
+// Original C++/Java/Python code:
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using Google.ProtocolBuffers.Descriptors;
+
+namespace Google.ProtocolBuffers {
+
+  /// <summary>
+  /// Non-generic interface used for all parts of the API which don't require
+  /// any type knowledge.
+  /// </summary>
+  public interface IMessage {
+    /// <summary>
+    /// Returns the message's type's descriptor. This differs from the
+    /// Descriptor property of each generated message class in that this
+    /// method is an abstract method of IMessage whereas Descriptor is
+    /// a static property of a specific class. They return the same thing.
+    /// </summary>
+    MessageDescriptor DescriptorForType { get; }
+    /// <summary>
+    /// Returns a collection of all the fields in this message which are set
+    /// and their corresponding values.  A singular ("required" or "optional")
+    /// field is set iff HasField() returns true for that field.  A "repeated"
+    /// field is set iff GetRepeatedFieldSize() is greater than zero.  The
+    /// values are exactly what would be returned by calling
+    /// GetField(FieldDescriptor) for each field.  The map
+    /// is guaranteed to be a sorted map, so iterating over it will return fields
+    /// in order by field number. 
+    /// </summary>
+    IDictionary<FieldDescriptor, object> AllFields { get; }
+
+    /// <summary>
+    /// Returns true if the given field is set. This is exactly equivalent
+    /// to calling the generated "Has" property corresponding to the field.
+    /// </summary>
+    /// <exception cref="ArgumentException">the field is a repeated field,
+    /// or it's not a field of this type</exception>
+    bool HasField(FieldDescriptor field);
+
+    /// <summary>
+    /// Obtains the value of the given field, or the default value if
+    /// it isn't set. For value type fields, the boxed value is returned.
+    /// For enum fields, the EnumValueDescriptor for the enum is returned.
+    /// For embedded message fields, the sub-message
+    /// is returned. For repeated fields, an IList&lt;T&gt; is returned.
+    /// </summary>
+    object this[FieldDescriptor field] { get; }
+
+    /// <summary>
+    /// Returns the number of elements of a repeated field. This is
+    /// exactly equivalent to calling the generated "Count" property
+    /// corresponding to the field.
+    /// </summary>
+    /// <exception cref="ArgumentException">the field is not a repeated field,
+    /// or it's not a field of this type</exception>
+    int GetRepeatedFieldCount(FieldDescriptor field);
+
+    /// <summary>
+    /// Gets an element of a repeated field. For value type fields 
+    /// excluding enums, the boxed value is returned. For embedded
+    /// message fields, the sub-message is returned. For enums, the
+    /// relevant EnumValueDescriptor is returned.
+    /// </summary>
+    /// <exception cref="ArgumentException">the field is not a repeated field,
+    /// or it's not a field of this type</exception>
+    /// <exception cref="ArgumentOutOfRangeException">the index is out of
+    /// range for the repeated field's value</exception>
+    object this[FieldDescriptor field, int index] { get; }
+
+    /// <summary>
+    /// Returns the unknown fields for this message.
+    /// </summary>
+    UnknownFieldSet UnknownFields { get; }
+
+    /// <summary>
+    /// Returns true iff all required fields in the message and all embedded
+    /// messages are set.
+    /// </summary>
+    bool IsInitialized { get; }
+
+    /// <summary>
+    /// Serializes the message and writes it to the given output stream.
+    /// This does not flush or close the stream.
+    /// </summary>
+    /// <remarks>
+    /// Protocol Buffers are not self-delimiting. Therefore, if you write
+    /// any more data to the stream after the message, you must somehow ensure
+    /// that the parser on the receiving end does not interpret this as being
+    /// part of the protocol message. One way of doing this is by writing the size
+    /// of the message before the data, then making sure you limit the input to
+    /// that size when receiving the data. Alternatively, use WriteDelimitedTo(Stream).
+    /// </remarks>
+    void WriteTo(CodedOutputStream output);
+
+    /// <summary>
+    /// Like WriteTo(Stream) but writes the size of the message as a varint before
+    /// writing the data. This allows more data to be written to the stream after the
+    /// message without the need to delimit the message data yourself. Use 
+    /// IBuilder.MergeDelimitedFrom(Stream) or the static method
+    /// YourMessageType.ParseDelimitedFrom(Stream) to parse messages written by this method.
+    /// </summary>
+    /// <param name="output"></param>
+    void WriteDelimitedTo(Stream output);
+
+    /// <summary>
+    /// Returns the number of bytes required to encode this message.
+    /// The result is only computed on the first call and memoized after that.
+    /// </summary>
+    int SerializedSize { get; }
+
+    #region Comparison and hashing
+    /// <summary>
+    /// Compares the specified object with this message for equality.
+    /// Returns true iff the given object is a message of the same type
+    /// (as defined by DescriptorForType) and has identical values
+    /// for all its fields.
+    /// </summary>
+    bool Equals(object other);
+
+    /// <summary>
+    /// Returns the hash code value for this message.
+    /// TODO(jonskeet): Specify the hash algorithm, but better than the Java one!
+    /// </summary>
+    int GetHashCode();
+    #endregion
+
+    #region Convenience methods
+    /// <summary>
+    /// Converts the message to a string in protocol buffer text format.
+    /// This is just a trivial wrapper around TextFormat.PrintToString.
+    /// </summary>
+    string ToString();
+
+    /// <summary>
+    /// Serializes the message to a ByteString. This is a trivial wrapper
+    /// around WriteTo(CodedOutputStream).
+    /// </summary>
+    ByteString ToByteString();
+
+    /// <summary>
+    /// Serializes the message to a byte array. This is a trivial wrapper
+    /// around WriteTo(CodedOutputStream).
+    /// </summary>
+    byte[] ToByteArray();
+
+    /// <summary>
+    /// Serializes the message and writes it to the given stream.
+    /// This is just a wrapper around WriteTo(CodedOutputStream). This
+    /// does not flush or close the stream.
+    /// </summary>
+    /// <param name="output"></param>
+    void WriteTo(Stream output);
+    #endregion
+
+    /// <summary>
+    /// Creates a builder for the type, but in a weakly typed manner. This
+    /// is typically implemented by strongly typed messages by just returning
+    /// the result of CreateBuilderForType.
+    /// </summary>
+    IBuilder WeakCreateBuilderForType();
+
+    /// <summary>
+    /// Creates a builder with the same contents as this message. This
+    /// is typically implemented by strongly typed messages by just returning
+    /// the result of ToBuilder.
+    /// </summary>
+    IBuilder WeakToBuilder();
+
+    IMessage WeakDefaultInstanceForType { get; }
+  }
+
+  public interface IMessage<TMessage> : IMessage {
+    /// <summary>
+    /// Returns an instance of this message type with all fields set to
+    /// their default values. This may or may not be a singleton. This differs
+    /// from the DefaultInstance property of each generated message class in that this
+    /// method is an abstract method of IMessage whereas DefaultInstance is
+    /// a static property of a specific class. They return the same thing.
+    /// </summary>
+    TMessage DefaultInstanceForType { get; }
+  }
+
+  /// <summary>
+  /// Type-safe interface for all generated messages to implement.
+  /// </summary>
+  public interface IMessage<TMessage, TBuilder> : IMessage<TMessage>
+      where TMessage : IMessage<TMessage, TBuilder> 
+      where TBuilder : IBuilder<TMessage, TBuilder> {
+    #region Builders
+    /// <summary>
+    /// Constructs a new builder for a message of the same type as this message.
+    /// </summary>
+    TBuilder CreateBuilderForType();
+    /// <summary>
+    /// Creates a builder with the same contents as this current instance.
+    /// This is typically implemented by strongly typed messages by just
+    /// returning the result of ToBuilder().
+    /// </summary>
+    TBuilder ToBuilder();
+    #endregion
+  }
+}