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Windows Embedded CE file filters are COM objects, usually compiled into DLLs, that reside on the desktop computer. ActiveSync uses these filters to convert file formats as files are transferred.

Because hand-held Windows Embedded CE-based devices generally have less storage space and RAM than desktop computers, their file formats are usually more compact than those for the same applications running on desktop computers. The size reduction is usually achieved by omitting functionality that is not as likely to be needed on a Windows Embedded CE-based device.

ActiveSync includes the following filters:

  • Word (.doc) to Word Mobile (.pwd)

  • Word Mobile (.pwd) to Word (.doc)

  • Windows bitmap (.bmp) to Windows Embedded CE 4-color bitmap (.2bp)

You can extend the file-filtering capability of ActiveSync by defining your own application-specific filters.

Implementing a file filter is similar for both importing and exporting files. The only differences are in the registry settings and in how the body of the file filter — the converter function — changes the data. The examples in this section demonstrate the procedure for importing files, but typically you would write a converter function that handles both importing and exporting. Such converter functions need two registry entries to indicate both the import and export functionality.

Importing and exporting are from the point of view of the Windows Embedded CE-based device. Importing transfers a file from the desktop computer to the Windows Embedded CE-based device. Exporting transfers a file from the Windows Embedded CE-based device to the desktop computer.


For an in-depth discussion of ActiveSync file filters, including a complete working sample, see the Microsoft Press book titled "Programming Windows Embedded CE," Second Edition, by Douglas Boling (ISBN 0-7356-1443-1).

See Also