When transferring binary files such as images over SOAP, the data must be serialized into XML. Serialization and deserialization can cause a significant amount of overhead. Therefore, it is common to send large binary files using an attachments mechanism. This keeps the binary data intact, reducing the parsing overhead.
Using attachments, the original data is sent outside the SOAP envelope, eliminating the need to serialize the data into XML and making the transfer of the data more efficient.
The formats used for passing a SOAP message together with binary data are MIME (Multipurpose Internet Mail Extensions) and the newer, more efficient DIME (Direct Internet Message Encapsulation) specifications. VuGen supports DIME for all toolkits, but MIME only for the Axis toolkit. To use MIME attachments for the .NET toolkit, see User Handler Examples.
VuGen supports the sending and receiving of attachments with SOAP messages. You can send Input (Request) or save Output (Response) attachments. For task details, see How to Add Content.
Output attachments are used to save the response as an attachment. You can choose one of the following options: Save All Attachments or Save Attachment by Index.
When you specify Save All Attachments, VuGen creates three parameters for each attachment based on the parameter name that your specify: a parameter containing the attachment data, the content type of the attachment, and a unique ID for the attachment.
For example, if you specify the name MyParam in the Content field, the parameter names for the first attachment would be:
MyParam_1 MyParam_1_ContentType MyParam_1_ContentID
When you specify Save Attachments by Index, you specify the index number and name of the parameter in which to store the attachment. The parameter name that you specify for Content, is used as a prefix for the Content type and Content ID parameters.