diff --git a/csharp/ProtocolBuffers.Test/ByteStringTest.cs b/csharp/ProtocolBuffers.Test/ByteStringTest.cs
index 5f701731fa..768d74fec5 100644
--- a/csharp/ProtocolBuffers.Test/ByteStringTest.cs
+++ b/csharp/ProtocolBuffers.Test/ByteStringTest.cs
@@ -1,5 +1,18 @@
-using System;
-using System.Collections.Generic;
+// 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.Text;
 using NUnit.Framework;
 
diff --git a/csharp/ProtocolBuffers.Test/CodedInputStreamTest.cs b/csharp/ProtocolBuffers.Test/CodedInputStreamTest.cs
index 8fefd98f21..8332140e5d 100644
--- a/csharp/ProtocolBuffers.Test/CodedInputStreamTest.cs
+++ b/csharp/ProtocolBuffers.Test/CodedInputStreamTest.cs
@@ -1,8 +1,21 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-using NUnit.Framework;
+// 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.IO;
+using NUnit.Framework;
 
 namespace Google.ProtocolBuffers {
   [TestFixture]
diff --git a/csharp/ProtocolBuffers.Test/CodedOutputStreamTest.cs b/csharp/ProtocolBuffers.Test/CodedOutputStreamTest.cs
index c2042d9e49..0e97f2fd9f 100644
--- a/csharp/ProtocolBuffers.Test/CodedOutputStreamTest.cs
+++ b/csharp/ProtocolBuffers.Test/CodedOutputStreamTest.cs
@@ -1,5 +1,20 @@
-using NUnit.Framework;
-using System.IO;
+using System.IO;
+// 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 NUnit.Framework;
 
 namespace Google.ProtocolBuffers {
   [TestFixture]
diff --git a/csharp/ProtocolBuffers/ByteString.cs b/csharp/ProtocolBuffers/ByteString.cs
index 1ce2453e3e..ba3e6512c2 100644
--- a/csharp/ProtocolBuffers/ByteString.cs
+++ b/csharp/ProtocolBuffers/ByteString.cs
@@ -1,4 +1,19 @@
-using System.Text;
+// 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.Text;
 using System;
 
 namespace Google.ProtocolBuffers {
diff --git a/csharp/ProtocolBuffers/Descriptors.cs b/csharp/ProtocolBuffers/Descriptors.cs
index ae09ee5a7c..4e5664327e 100644
--- a/csharp/ProtocolBuffers/Descriptors.cs
+++ b/csharp/ProtocolBuffers/Descriptors.cs
@@ -1,4 +1,18 @@
-
+// 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;
 
 namespace Google.ProtocolBuffers {
diff --git a/csharp/ProtocolBuffers/ExtensionRegistry.cs b/csharp/ProtocolBuffers/ExtensionRegistry.cs
index 54d86ad705..a8ed661d8a 100644
--- a/csharp/ProtocolBuffers/ExtensionRegistry.cs
+++ b/csharp/ProtocolBuffers/ExtensionRegistry.cs
@@ -1,4 +1,18 @@
-
+// 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.
 namespace Google.ProtocolBuffers {
   public class ExtensionRegistry {
   }
diff --git a/csharp/ProtocolBuffers/IBuilder.cs b/csharp/ProtocolBuffers/IBuilder.cs
index bf4f46ff05..3378aa9283 100644
--- a/csharp/ProtocolBuffers/IBuilder.cs
+++ b/csharp/ProtocolBuffers/IBuilder.cs
@@ -1,4 +1,19 @@
-using System;
+// 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 System.IO;
 
diff --git a/csharp/ProtocolBuffers/IMessage.cs b/csharp/ProtocolBuffers/IMessage.cs
index 109b2bfd0b..465d4b4543 100644
--- a/csharp/ProtocolBuffers/IMessage.cs
+++ b/csharp/ProtocolBuffers/IMessage.cs
@@ -1,4 +1,19 @@
-using System;
+// 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 System.IO;
 
diff --git a/csharp/ProtocolBuffers/InvalidProtocolBufferException.cs b/csharp/ProtocolBuffers/InvalidProtocolBufferException.cs
index db16ca8f20..091ac2b7c5 100644
--- a/csharp/ProtocolBuffers/InvalidProtocolBufferException.cs
+++ b/csharp/ProtocolBuffers/InvalidProtocolBufferException.cs
@@ -1,4 +1,18 @@
-using System;
+// 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.IO;
 
 namespace Google.ProtocolBuffers {
diff --git a/csharp/ProtocolBuffers/ProtocolBuffers.csproj b/csharp/ProtocolBuffers/ProtocolBuffers.csproj
index 196f46d334..e2486203bc 100644
--- a/csharp/ProtocolBuffers/ProtocolBuffers.csproj
+++ b/csharp/ProtocolBuffers/ProtocolBuffers.csproj
@@ -36,6 +36,7 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="AbstractMessage.cs" />
     <Compile Include="ByteString.cs" />
     <Compile Include="CodedInputStream.cs" />
     <Compile Include="CodedOutputStream.cs" />
diff --git a/csharp/ProtocolBuffers/UninitializedMessageException.cs b/csharp/ProtocolBuffers/UninitializedMessageException.cs
index a77499af71..949341d901 100644
--- a/csharp/ProtocolBuffers/UninitializedMessageException.cs
+++ b/csharp/ProtocolBuffers/UninitializedMessageException.cs
@@ -1,4 +1,19 @@
-using System;
+// 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;
 
 namespace Google.ProtocolBuffers {
   public class UninitializedMessageException : Exception {
diff --git a/csharp/ProtocolBuffers/UnknownFieldSet.cs b/csharp/ProtocolBuffers/UnknownFieldSet.cs
index 1a452fa7e8..b9bbfe3ae4 100644
--- a/csharp/ProtocolBuffers/UnknownFieldSet.cs
+++ b/csharp/ProtocolBuffers/UnknownFieldSet.cs
@@ -1,6 +1,19 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
+// 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;
 
 namespace Google.ProtocolBuffers {
   public class UnknownFieldSet {
diff --git a/csharp/ProtocolBuffers/WireFormat.cs b/csharp/ProtocolBuffers/WireFormat.cs
index b100e52050..ade1ebb180 100644
--- a/csharp/ProtocolBuffers/WireFormat.cs
+++ b/csharp/ProtocolBuffers/WireFormat.cs
@@ -1,7 +1,18 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
+// 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.
 namespace Google.ProtocolBuffers {
   public class WireFormat {
     public enum WireType : uint {