Programming WCF Services

Streaming

By default, when the client and the service exchange messages, these messages are buffered on the receiving end and delivered once the entire message is received. This is true whether it is the client sending a message to the service or the service returning a message to the client. When the client calls the service, the service is invoked when the message is received in its entirety. The client is unblocked when the returned message with the results of the invocation is received in its entirety. For sufficiently small message sizes, this exchange pattern provides for a simple programming model because the latency caused by receiving the message is usually negligible compared with the message processing itself. However, when it comes to much larger messages, such as ones involving multimedia content, large files, or batches of data, blocking every time until the message is received may be impractical. To handle such cases, WCF enables the receiving side (be it the client or the service) to start processing the data in the message while the message is still being received by the channel. Such processing is called streaming transfer mode. With large payloads, streaming provides improved throughput and responsiveness because neither the receiving nor sending side is blocked when sending or receiving the message.

I/O Streams

For message streaming, WCF requires the use of the .NET Stream class. In fact, the contract operations used for streaming look just like conventional ...