add missing copyright

src/csharp/Grpc.Core.Api/Utils/EncodingExtensions.cs

@@ -1,3 +1,19 @@
+#region Copyright notice and license
+// Copyright 2015 gRPC authors.
+//
+// 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.
+#endregion
+
 using System;
 using System.Runtime.CompilerServices;
 using System.Text;

src/csharp/Grpc.Core.Tests/Internal/WellKnownStringsTest.cs

@@ -1,3 +1,19 @@
+#region Copyright notice and license
+// Copyright 2015 gRPC authors.
+//
+// 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.
+#endregion
+
 using System.Text;
 using Grpc.Core.Internal;
 using NUnit.Framework;

src/csharp/Grpc.Core/Internal/WellKnownStrings.cs

@@ -1,6 +1,21 @@
+#region Copyright notice and license
+// Copyright 2015 gRPC authors.
+//
+// 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.
+#endregion
+
 using System;
 using System.Runtime.CompilerServices;
-using System.Text;
 
 namespace Grpc.Core.Internal
 {