Fixes for .NET 3.5 compatibility

* Changing DOTNET35 framework symbols in preprocessor directives to the default built-in value of NET35.
* Adding extension method StreamExtension.CopyTo for .NET 3.5 because it didn’t exist until .NET 4, and adding associated unit tests.

3 files changed, 69 insertions, 3 deletions

diff --git a/csharp/src/Google.Protobuf/Compatibility/PropertyInfoExtensions.cs b/csharp/src/Google.Protobuf/Compatibility/PropertyInfoExtensions.cs
index e3914dd3..95a02c72 100644..100755
--- a/csharp/src/Google.Protobuf/Compatibility/PropertyInfoExtensions.cs
+++ b/csharp/src/Google.Protobuf/Compatibility/PropertyInfoExtensions.cs
@@ -47,7 +47,7 @@ namespace Google.Protobuf.Compatibility
         /// </summary>
         internal static MethodInfo GetGetMethod(this PropertyInfo target)
         {
-#if DOTNET35
+#if NET35
             var method = target.GetGetMethod();
 #else
             var method = target.GetMethod;
@@ -61,7 +61,7 @@ namespace Google.Protobuf.Compatibility
         /// </summary>
         internal static MethodInfo GetSetMethod(this PropertyInfo target)
         {
-#if DOTNET35
+#if NET35
             var method = target.GetSetMethod();
 #else
             var method = target.SetMethod;
diff --git a/csharp/src/Google.Protobuf/Compatibility/StreamExtensions.cs b/csharp/src/Google.Protobuf/Compatibility/StreamExtensions.cs
new file mode 100755
index 00000000..bf4bf220
--- /dev/null
+++ b/csharp/src/Google.Protobuf/Compatibility/StreamExtensions.cs
@@ -0,0 +1,66 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// 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
+
+#if NET35
+using System;
+using System.IO;
+
+namespace Google.Protobuf.Compatibility
+{
+    /// <summary>
+    /// Extension methods for <see cref="Stream"/> in order to provide
+    /// backwards compatibility with .NET 3.5
+    /// </summary>
+    public static class StreamExtensions
+    {
+        // 81920 seems to be the default buffer size used in .NET 4.5.1
+        private const int BUFFER_SIZE = 81920;
+
+        /// <summary>
+        /// Write the contents of the current stream to the destination stream
+        /// </summary>
+        public static void CopyTo(this Stream source, Stream destination)
+        {
+            if (destination == null)
+            {
+                throw new ArgumentNullException(nameof(destination));
+            }
+
+            byte[] buffer = new byte[BUFFER_SIZE];
+            int numBytesRead;
+            while ((numBytesRead = source.Read(buffer, 0, buffer.Length)) > 0) {
+                destination.Write(buffer, 0, numBytesRead);
+            }
+        }
+    }
+}
+#endif
diff --git a/csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs b/csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs
index 2d93183b..2f237138 100644..100755
--- a/csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs
+++ b/csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs
@@ -33,7 +33,7 @@
 using System;
 using System.Reflection;
 
-#if !DOTNET35
+#if !NET35
 namespace Google.Protobuf.Compatibility
 {
     /// <summary>