First cut at new layout
diff --git a/src/ProtocolBuffers/GeneratedMessage.cs b/src/ProtocolBuffers/GeneratedMessage.cs
new file mode 100644
index 0000000..7801d52
--- /dev/null
+++ b/src/ProtocolBuffers/GeneratedMessage.cs
@@ -0,0 +1,139 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.
+// http://code.google.com/p/protobuf/
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+using System;
+using System.Collections.Generic;
+using Google.ProtocolBuffers.Collections;
+using Google.ProtocolBuffers.Descriptors;
+using Google.ProtocolBuffers.FieldAccess;
+using System.Collections;
+
+namespace Google.ProtocolBuffers {
+  
+  /// <summary>
+  /// All generated protocol message classes extend this class. It implements
+  /// most of the IMessage interface using reflection. Users
+  /// can ignore this class as an implementation detail.
+  /// </summary>
+  public abstract class GeneratedMessage<TMessage, TBuilder> : AbstractMessage<TMessage, TBuilder>
+      where TMessage : GeneratedMessage<TMessage, TBuilder> 
+      where TBuilder : GeneratedBuilder<TMessage, TBuilder> {
+
+    private UnknownFieldSet unknownFields = UnknownFieldSet.DefaultInstance;
+
+    /// <summary>
+    /// Returns the message as a TMessage.
+    /// </summary>
+    protected abstract TMessage ThisMessage { get; }
+
+    internal FieldAccessorTable<TMessage, TBuilder> FieldAccessorsFromBuilder {
+      get { return InternalFieldAccessors; }
+    }
+
+    protected abstract FieldAccessorTable<TMessage, TBuilder> InternalFieldAccessors { get; }
+
+    public override MessageDescriptor DescriptorForType {
+      get { return InternalFieldAccessors.Descriptor; }
+    }
+
+    internal IDictionary<FieldDescriptor, Object> GetMutableFieldMap() {
+
+      // Use a SortedList so we'll end up serializing fields in order
+      var ret = new SortedList<FieldDescriptor, object>();
+      MessageDescriptor descriptor = DescriptorForType;
+      foreach (FieldDescriptor field in descriptor.Fields) {
+        IFieldAccessor<TMessage, TBuilder> accessor = InternalFieldAccessors[field];
+        if (field.IsRepeated) {
+          if (accessor.GetRepeatedCount(ThisMessage) != 0) {
+            ret[field] = accessor.GetValue(ThisMessage);
+          }
+        } else if (HasField(field)) {
+          ret[field] = accessor.GetValue(ThisMessage);
+        }
+      }
+      return ret;
+    }
+
+    public override bool IsInitialized {
+      get {
+       /* if (!DescriptorForType.HasRequiredFields) {
+          return true;
+        }*/
+        // Check that all required fields are present.
+        foreach (FieldDescriptor field in DescriptorForType.Fields) {
+          if (field.IsRequired && !HasField(field)) {
+            return false;
+          }
+        }
+
+        // Check that embedded messages are initialized.
+        // This code is similar to that in AbstractMessage, but we don't
+        // fetch all the field values - just the ones we need to.
+        foreach (FieldDescriptor field in DescriptorForType.Fields) {
+          if (field.MappedType == MappedType.Message) {
+            if (field.IsRepeated) {
+              // We know it's an IList<T>, but not the exact type - so
+              // IEnumerable is the best we can do. (C# generics aren't covariant yet.)
+              foreach (IMessage element in (IEnumerable) this[field]) {
+                if (!element.IsInitialized) {
+                  return false;
+                }
+              }
+            } else {
+              if (HasField(field) && !((IMessage) this[field]).IsInitialized) {
+                return false;
+              }
+            }
+          }
+        }
+        return true;
+      }
+    }
+
+    public override IDictionary<FieldDescriptor, object> AllFields {
+      get { return Dictionaries.AsReadOnly(GetMutableFieldMap()); }
+    }
+
+    public override bool HasField(FieldDescriptor field) {
+      return InternalFieldAccessors[field].Has(ThisMessage);
+    }
+
+    public override int GetRepeatedFieldCount(FieldDescriptor field) {
+      return InternalFieldAccessors[field].GetRepeatedCount(ThisMessage);
+    }
+
+    public override object this[FieldDescriptor field, int index] {
+      get { return InternalFieldAccessors[field].GetRepeatedValue(ThisMessage, index); }
+    }
+
+    public override object this[FieldDescriptor field] {
+      get { return InternalFieldAccessors[field].GetValue(ThisMessage); }
+    }
+
+    public override UnknownFieldSet UnknownFields {
+      get { return unknownFields; }
+    }
+
+    /// <summary>
+    /// Replaces the set of unknown fields for this message. This should
+    /// only be used before a message is built, by the builder. (In the
+    /// Java code it is private, but the builder is nested so has access
+    /// to it.)
+    /// </summary>
+    internal void SetUnknownFields(UnknownFieldSet fieldSet) {
+      unknownFields = fieldSet;
+    }    
+  }
+}