Public Class SaveFileRequest. Public Class FileService. Implements IFileService. End Sub. End Function. Public Interface IFileService. End Interface. Do take note that when retrieving the stream from a physical file through File class, make sure to close and dispose the File class after moved the content into a stream to prevent the file being locked by your application.
There are few things you can configure in web configuration file. To send or receive file in stream, change the attribute "transferMode" to "Streamed" in binding element. By default, "transferMode" is "buffered", what this mean is WCF will hold the content in memory until the file is transferred, in which will lead to very high memory usage if transferring a large file.
The second attribute that you can configured is " maxReceivedMessageSize ". Write s ; writer. Flush ; stream. Clear Response. Write s Response. End This would automatically initiate a file download of "file1. See this post here on SO to see how to start a download from JavaScript. This has been answered stackoverflow.
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Who owns this outage? For returning streamed data, return a Stream reference. The operation Echo in the preceding example receives and returns a stream and should therefore be used on a binding with Streamed. The one-way operation is best suited for StreamedRequest. Note that adding a second parameter to the following Echo or ProvideInfo operations causes the service model to revert back to a buffered strategy and use the run-time serialization representation of the stream.
Only operations with a single input stream parameter are compatible with end-to-end request streaming. This rule similarly applies to message contracts. As shown in the following message contract, you can have only a single body member in your message contract that is a stream. If you want to communicate additional information with the stream, this information must be a carried in message headers.
The message body is exclusively reserved for the stream content. Streamed transfers end and the message is closed when the stream reaches the end of file EOF. When sending a message returning a value or invoking an operation , you can pass a FileStream and the WCF infrastructure subsequently pulls all the data from that stream until the stream has been completely read and reached EOF.
To transfer streamed data for the source that no such pre-built Stream derived class exists, construct such a class, overlay that class over your stream source, and use that as the argument or return value.
Transport-level streaming also works with any other message contract type parameter lists, data contract arguments, and explicit message contract , but because the serialization and deserialization of such typed messages requires buffering by the serializer, using such contract variants is not advisable.
All bindings allow you to constrain the size of incoming messages to prevent denial-of-service attacks. The BasicHttpBinding, for example, exposes a System. MaxReceivedMessageSize property that bounds the size of the incoming message, and so also bounds the maximum amount of memory that is accessed when processing the message. This unit is set in bytes with a default value of 65, bytes. A security threat that is specific to the large data streaming scenario provokes a denial of service by causing data to be buffered when the receiver expects it to be streamed.
For example, WCF always buffers the SOAP headers of a message, and so an attacker may construct a large malicious message that consists entirely of headers to force the data to be buffered. When streaming is enabled, the MaxReceivedMessageSize may be set to an extremely large value, because the receiver never expects the entire message to be buffered in memory at once. If WCF is forced to buffer the message, a memory overflow occurs.
Therefore, restricting the maximum incoming message size is not enough in this case. It is important to set this to a safe value or keep it at the default value when streaming.
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.
Also, in your service implementation, you must ensure that you read only from the incoming stream in KB chunks and do not read the next chunk before the previous one has been written to disk and discarded from memory.
It is also important to understand that this quota only limits the buffering done by WCF and cannot protect you against any buffering that you do in your own service or client implementation. For more information about additional security considerations, see Security Considerations for Data. The decision to use either buffered or streamed transfers is a local decision of the endpoint. For HTTP transports, the transfer mode does not propagate across a connection or to proxy servers and other intermediaries.
Setting the transfer mode is not reflected in the description of the service interface. After generating a WCF client to a service, you must edit the configuration file for services intended to be used with streamed transfers to set the mode.
For TCP and named pipe transports, the transfer mode is propagated as a policy assertion. Basic Considerations To provide background information about the following information for WCF, this section highlights some general concerns and considerations for encodings, binary data, and streaming that generally apply to connected systems infrastructures.
Encoding Data: Text vs. Binary Commonly expressed developer concerns include the perception that XML has significant overhead when compared to binary formats due to the repetitive nature of start tags and end tags, that the encoding of numerical values is considered to be significantly larger because they are expressed in text values, and that binary data cannot be expressed efficiently because it must be specially encoded for embedding into a text format.
Binary Content One area where binary encodings are superior to text-based encodings in terms of the resulting message size are large binary data items such as pictures, videos, sound clips, or any other form of opaque, binary data that must be exchanged between services and their consumers.
Large Data Content Wire-footprint aside, the previously mentioned MB payload also poses a great local challenge at for the service and the client. The most common scenario in which such large data content transfers occur are transfers of binary data objects that: Cannot be easily broken up into a message sequence. Must be delivered in a timely manner. Are not available in their entirety when the transfer is initiated.
Encodings An encoding defines a set of rules about how to present messages on the wire. WCF includes three encoders and allows you to write and plug in your own encoders, if necessary. Encoder binding element Description TextMessageEncodingBindingElement The text message encoder is the default encoder for all HTTP-based bindings and the appropriate choice for all custom bindings where interoperability is the highest concern.
This encoder reads and writes standard SOAP 1. If the System. MessageVersion property of a message is set to MessageVersion. None, the SOAP envelope wrapper is omitted from the output and only the message body content is serialized. MtomMessageEncodingBindingElement The MTOM message encoder is a text encoder that implements special handling for binary data and is not used by default in any of the standard bindings because it is strictly a case-by-case optimization utility.
If the message contains binary data that exceeds a threshold where MTOM encoding yields a benefit, the data is externalized into a MIME part following the message envelope. The binary message encoder uses the. Programming Model Regardless of which of the three built-in encoders you use in your application, the programming experience is identical with regards to transferring binary data.
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