MessageEncoder Class

The encoder is the component that is used to write messages to a stream and to read messages from a stream.

Namespace:  System.ServiceModel.Channels
Assembly:  System.ServiceModel (in System.ServiceModel.dll)

public abstract class MessageEncoder

MessageEncoder is a base class that provides implementations that support a Multipurpose Internet Mail Extensions (MIME) content type and message version, and defines the interface for the serialization and deserialization of messages according to that content type. Use it as a base class for writing your own custom encoder.

Use this class if you want to implement a custom message encoder. To implement your own custom message encoder, you must provide custom implementations of the following abstract base classes:

Override the Encoder to return an instance of your custom MessageEncoder. Then wire up your custom MessageEncoderFactory to the binding element stack used to configure the service or client by overriding the CreateMessageEncoderFactory method to return an instance of this factory.

The task of converting between the in-memory representation of a message and an XML Information Set (Infoset) representation that can be written to a stream is encapsulated within the MessageEncoder class, which most commonly serves as a factory for XML readers and XML writers that support specific types of XML encodings.

The key methods on MessageEncoder are WriteMessage and ReadMessage. WriteMessage takes a Message object and writes it into a Stream object. ReadMessage takes a Stream object and a maximum header size and returns a Message object.

The following code shows an example of a class that is derived from MessageEncoder.

public class CustomTextMessageEncoder : MessageEncoder
{
    private CustomTextMessageEncoderFactory factory;
    private XmlWriterSettings writerSettings;
    private string contentType;

    public CustomTextMessageEncoder(CustomTextMessageEncoderFactory factory)
    {
        this.factory = factory;

        this.writerSettings = new XmlWriterSettings();
        this.writerSettings.Encoding = Encoding.GetEncoding(factory.CharSet);
        this.contentType = string.Format("{0}; charset={1}", 
            this.factory.MediaType, this.writerSettings.Encoding.HeaderName);
    }

    public override string ContentType
    {
        get
        {
            return this.contentType;
        }
    }

    public override string MediaType
    {
        get 
        {
            return factory.MediaType;
        }
    }

    public override MessageVersion MessageVersion
    {
        get 
        {
            return this.factory.MessageVersion;
        }
    }

    public override bool IsContentTypeSupported(string contentType) 
    { 
        if (base.IsContentTypeSupported(contentType)) 
        { 
            return true; 
        } 
        if (contentType.Length == this.MediaType.Length) 
        { 
            return contentType.Equals(this.MediaType, StringComparison.OrdinalIgnoreCase); 
        } 
        else 
        { 
            if (contentType.StartsWith(this.MediaType, StringComparison.OrdinalIgnoreCase) 
                && (contentType[this.MediaType.Length] == ';')) 
            { 
                return true; 
            } 
        } 
        return false; 
    }

    public override Message ReadMessage(ArraySegment<byte> buffer, BufferManager bufferManager, string contentType)
    {   
        byte[] msgContents = new byte[buffer.Count];
        Array.Copy(buffer.Array, buffer.Offset, msgContents, 0, msgContents.Length);
        bufferManager.ReturnBuffer(buffer.Array);

        MemoryStream stream = new MemoryStream(msgContents);
        return ReadMessage(stream, int.MaxValue);
    }

    public override Message ReadMessage(Stream stream, int maxSizeOfHeaders, string contentType)
    {
        XmlReader reader = XmlReader.Create(stream);
        return Message.CreateMessage(reader, maxSizeOfHeaders, this.MessageVersion);
    }

    public override ArraySegment<byte> WriteMessage(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset)
    {
        MemoryStream stream = new MemoryStream();
        XmlWriter writer = XmlWriter.Create(stream, this.writerSettings);
        message.WriteMessage(writer);
        writer.Close();

        byte[] messageBytes = stream.GetBuffer();
        int messageLength = (int)stream.Position;
        stream.Close();

        int totalLength = messageLength + messageOffset;
        byte[] totalBytes = bufferManager.TakeBuffer(totalLength);
        Array.Copy(messageBytes, 0, totalBytes, messageOffset, messageLength);

        ArraySegment<byte> byteArray = new ArraySegment<byte>(totalBytes, messageOffset, messageLength);
        return byteArray;
    }

    public override void WriteMessage(Message message, Stream stream)
    {
        XmlWriter writer = XmlWriter.Create(stream, this.writerSettings);
        message.WriteMessage(writer);
        writer.Close();
    }

System.Object
  System.ServiceModel.Channels.MessageEncoder

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0

.NET Compact Framework

Supported in: 3.5
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