The compression options for WCF out of the box are limited in .Net 4.0. However, a sample is provided for GZip compression that shows you how to write your own MessageEncoder that can wrap the output of another encoder and apply GZip to the messages. If your environment has a network bandwidth limitation, compressing the messages going across the wire could be very helpful. In this series, we will be taking a look at how to use the GZip message encoder and what effect it has on your performance.
Download the WCF/WF Samples from here: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=35ec8682-d5fd-4bc3-a51a-d8ad115a8792&displaylang=en
The first thing to do is examine the code for GZipMessageEncoder itself. Let's open up the solution. Download and install the WCF/WF samples to the directory of your choice. Then navigate to the WCF/Extensibility/MessageEncoder/Compression/CS directory and open the solution. Right-click on the solution in the solution explorer pane and choose "Set Startup Projects". Choose the Multiple startup projects radio button and use the dropdown to change the client and service projects' actions to "Start". Then you should be able to hit F5. The service and client windows should come up and execute, exchanging a couple messages back and forth.
The GZipMessageEncoder works by using another encoder underneath. In the sample, buffered messages are used. This means that the entire message is stored in a single continguous byte[]. We can examine the effect of compression on the buffered message by altering the code a bit to write the sizes before and after compression. To do this, open the GZipMessageEncodeFactory.cs file. Navigate to the GZipMessageEncoder class and the WriteMessage method that returns an ArraySegment<byte>. Alter the code as shown below:
//One of the two main entry points into the encoder. Called by WCF to encode a Message into a buffered byte array.
public override ArraySegment<byte> WriteMessage(Message message, int maxMessageSize,
BufferManager bufferManager, int messageOffset)
{
//Use the inner encoder to encode a Message into a buffered byte array
ArraySegment<byte> buffer = innerEncoder.WriteMessage(message, maxMessageSize,
bufferManager, 0);
//Compress the resulting byte array
System.Diagnostics.Debug.WriteLine("Original size: {0}", buffer.Count);
buffer = CompressBuffer(buffer, bufferManager, messageOffset);
System.Diagnostics.Debug.WriteLine("Compressed size: {0}", buffer.Count);
return buffer;
}
This just writes to diagnostics the size of the buffer. Here we can see how well our messages are being compressed. Hit F5 again to run and then bring up the Output view window in Visual Studio. You should see something like this:
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