It is possible to use RAPI calls in a file filter. This allows use of any RAPI functions that are appropriate to your application, such as registry or file functions.
Do not initialize RAPI in the file filter DLL by using CeRapiInit. Rather, the NextConvertFile method should have already performed the RAPI initialization and established a connection between the desktop computer and the Windows CE-based device. If a RAPI call fails because there is no connection established, the file converter should perform some type of default action rather than just failing. For example, this default action could involve querying the user to select from various options.
To determine if a call failed due to a failure in the RAPI, use CeRapiGetError. To diagnose non-RAPI related errors, use CeGetLastError.
For more information on RAPI, see Invoking Functions from a Desktop Computer.