Implementing a Dummy File Filter

A dummy file filter gives the appearance that files are being converted without actually implementing a file filter or performing a filter conversion. Instead, the file is passed without any conversion whatsoever.

Implementing such a dummy filter may be desirable for a file that has a unique file type or one that has not been registered already in the desktop registry. It might also be useful for a file that does not need any conversion when it is transferred between Windows Explorer on the desktop computer and Explorer for the device.

Usually, if a file with an unregistered file type is copied to the device, the device will display the warning No Converter Selected. This warns the user that the file will be transferred without conversion. In this situation, implementing a dummy filter would avoid alarming the user with the file conversion warning.

Note The No Converter Selected warning will be displayed only if the mobile device's File Conversions Properties is set to enable file conversion. If the Enable File Conversion check box is unchecked, then the No Converter Selected warning will not be displayed.

    To register a dummy file filter

1. Modify HKLM\Software\Microsoft\Windows CE Services\Filters, the desktop computer registry key, by adding a subkey. This subkey should name the file extension for the type of files that should be converted using the NULL file conversion. For example, if you are converting files with extension .abc, then you must add a subkey .abc.
2. Under the .abc subkey, create a string value named DefaultImport that is set to Binary Copy. This string value identifies the conversion for files with .abc extensions that are imported from the desktop computer to the Windows CE-based device.
3. Under the .abc subkey, create a string value named DefaultExport that is set to Binary Copy. This identifies the conversion for files with .abc extensions that are exported from the device to the desktop computer.

The following registry editor (.reg) file registers the example .abc dummy file filter.

REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows CE Services\Filters\.abc]
"DefaultImport"="Binary Copy"
"DefaultExport"="Binary Copy"

In this example, when a file with an .abc extension is copied between the desktop computer and the Windows CE-based device, it will seem as though a conversion process is taking place because you do not receive the warning No Converter Selected from Windows CE Services. However, no filter actually is being used, because an InstalledFilters subkey has not been added under the .abc key.

Table Revision History