Problem of setting MaxReceivedMessageSize and MaxBufferSize in WCF application

I am implementing a large file streaming application using WCF.

I got a issue when I set the configuration for MaxReceivedMessageSize and MaxBufferSize. When these parameters are same system works fine. 开发者_如何学PythonBut when I chose different value it gives an error message,

For TransferMode.Buffered, MaxReceivedMessageSize and MaxBufferSize must be the same value.

But I confused with the information in http://msdn.microsoft.com/en-us/library/ms733742.aspx as follows,

For example, suppose your service must receive files up to 4 GB in size and store them on the local disk. Suppose also that your memory is constrained in such a way that you can only buffer 64 KB of data at a time. Then you would set the MaxReceivedMessageSize to 4 GB and MaxBufferSize to 64 KB. Also, in your service implementation, you must ensure that you read only from the incoming stream in 64-KB chunks and do not read the next chunk before the previous one has been written to disk and discarded from memory.to 4 GB and MaxBufferSize to 64 KB. Also, in your service implementation, you must ensure that you read only from the incoming stream in 64-KB chunks and do not read the next chunk before the previous one has been written to disk and discarded from memory.

Can anybody explain the reason of this matter?

It's because of the TransferMode. You should set it to streamed, if you want to use a different buffer size than message size.

transports support two modes of transferring messages in each direction:

• Buffered transfers hold the entire message in a memory buffer until the transfer is complete.

• Streamed transfers only buffer the message headers and expose the message body as a stream, from which smaller portions can be read at a time.