Compressing messages in WCF part two - Expanding the GZipMessageEncoder and fixing another bug

The GZipMessageEncoder is a great sample for learning about MessageEncoders in general. In this post, I will expand the GZipMessageEncoder to do both GZip and Deflate compression. This will accomplish two things: (1) explain various pieces of a MessageEncoder and (2) set a groundwork for future posts.

Since the MessageEncoder will now support both GZip and Deflate, it would be a good idea to change the name. To do this I did a replace in all files from "GZipMessageEncod" to "MyCompressionMessageEncod":

I did the same thing with "GZipEncoder" to "CompressionEncoder" to change the namespace. I also changed the assembly name in the solution explorer and in the project properties. Then I changed the filenames in the project. You can try to repeat all these steps or just download the finished code.

The first thing that is needed is a switch to flip between GZip and Deflate. Since my plan is to enable more than just GZip and Deflate in later posts, this should be an enum. 

namespace Microsoft.Samples.CompressionEncoder

{

    public enum CompressionAlgorithm

    {

        GZip,

        Deflate,

    }

}

In order to enable this switch there are a lot of places that have to change. The first thing I'll change is the binding element. This is what is used by WCF to configure the binding.

//This is the binding element that, when plugged into a custom binding, will enable the GZip encoder

public sealed class MyCompressionMessageEncodingBindingElement 

                    : MessageEncodingBindingElement //BindingElement

                    , IPolicyExportExtension

{

    //We will use an inner binding element to store information required for the inner encoder

    MessageEncodingBindingElement innerBindingElement;

    CompressionAlgorithm compressionAlgorithm;

    //By default, use the default text encoder as the inner encoder

    public MyCompressionMessageEncodingBindingElement()

        : this(new TextMessageEncodingBindingElement(), CompressionAlgorithm.GZip) { }

    public MyCompressionMessageEncodingBindingElement(

        MessageEncodingBindingElement messageEncoderBindingElement, 

        CompressionAlgorithm compressionAlgorithm)

    {

        this.innerBindingElement = messageEncoderBindingElement;

        this.compressionAlgorithm = compressionAlgorithm;

    }

    public MessageEncodingBindingElement InnerMessageEncodingBindingElement

    {

        get { return innerBindingElement; }

        set { innerBindingElement = value; }

    }

Read more: Dustin Metzgar's blog

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