A binding consists of an ordered set of binding elements that inherit from this abstract base class. The TransportBindingElement class inherits from the BindingElement class.

Creating a binding and binding element for your transport is optional if you are just using the channel model. It is possible to do everything you need through the channel factory and listener as long as they are made public.

The Windows Communication Foundation (WCF) service model uses a factory pattern where the binding is used to create the channel stack. If you want to use the WCF service model, then using a transport binding element is required. Placing this binding element into a binding is a good practice because it removes the requirement for users to create their own custom binding for your transport. It is best to create both a binding and binding element, and hide the channel factory and listener inside the assembly.

On the sending side, a binding is used to build a IChannelFactory, which in turn builds a channel stack and returns a reference to the top channel in the stack. The application can then use this channel to send messages.

Similarly, on the receiving side a binding is used to build a IChannelListener, which listens for incoming messages. The IChannelListener provides messages to the listening application by creating channel stacks and handing the application a reference to the top channel. The application then uses this channel to receive incoming messages.

Note:
If you are adding message headers that must be encrypted you must return a ChannelProtectionRequirements instance with your requirements from the GetProperty<(Of <(T>)>)(BindingContext) method when asked for ChannelProtectionRequirements.

The following example shows how to add a transport binding element to a custom binding and then build a channel listener that can accept incoming messages.

Dim binding As New CustomBinding()
binding.Elements.Add(New HttpTransportBindingElement())
Dim paramCollection As New BindingParameterCollection()

Dim listener As IChannelListener(Of IReplyChannel)
listener = binding.BuildChannelListener(Of IReplyChannel)(New Uri("http://localhost/channelApp"), paramCollection)

listener.Open()
Dim channel As IReplyChannel = listener.AcceptChannel()
Console.WriteLine("Listening for messages")
channel.Open()
Dim request As RequestContext = channel.ReceiveRequest()
Dim msg As Message = request.RequestMessage
Console.WriteLine("Message Received")
Console.WriteLine("Message Action: {0}", msg.Headers.Action)

If (msg.Headers.Action = "hello") Then

    Dim reply As Message = Message.CreateMessage(MessageVersion.Default, "wcf")
    request.Reply(reply)
End If

msg.Close()
channel.Close()
listener.Close()

CustomBinding binding = new CustomBinding();
binding.Elements.Add(new HttpTransportBindingElement());
BindingParameterCollection paramCollection = new BindingParameterCollection();
IChannelListener<IReplyChannel> listener = binding.BuildChannelListener<IReplyChannel>
    (new Uri("http://localhost:8000/ChannelApp"), paramCollection);

listener.Open();
IReplyChannel channel = listener.AcceptChannel();
Console.WriteLine("Listening for messages");
channel.Open();
RequestContext request = channel.ReceiveRequest();
Message msg = request.RequestMessage;
Console.WriteLine("Message Received");
Console.WriteLine("Message Action: {0}", msg.Headers.Action);

if (msg.Headers.Action == "hello")
{
    Message reply = Message.CreateMessage(MessageVersion.Default, "wcf");
    request.Reply(reply);
}

msg.Close();
channel.Close();
listener.Close();

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

.NET Framework

.NET Compact Framework

Reference