Acting as a Host Address Book Provider

A host provider is an address book provider that includes recipients from other providers in its containers and relies on the implementation of the recipients by the other providers to partially control their maintenance. A host provider uses the template identifiers of these foreign recipients to bind the data for these recipients to code in the foreign provider. This binding process is initiated when your provider retrieves the PR_TEMPLATEID property of a recipient and passes it in a call to IMAPISupport::OpenTemplateID.

When your provider calls IMAPISupport::OpenTemplateID, MAPI matches the MAPIUID within the template identifier with a MAPIUID registered by a provider and calls the provider's IABLogon::OpenTemplateID method. The foreign provider might return a pointer to your provider's property object or its own property object implementation, an implementation that wraps your provider's object. The returned pointer is placed in the contents of the lppMAPIPropNew parameter.

Your provider can choose whether or not to call IMAPISupport::OpenTemplateID with the FILL_ENTRY flag set. Set this flag when the recipient is being created or when a long time has passed since your provider has refreshed the recipient's properties. A common use of the FILL_ENTRY flag is to keep a recipient in your provider synchronized with the original. Implementing this type of synchronization schedule enhances performance.

To keep a foreign recipient synchronized

1. Determine an appropriate interval for periodic updates.
2. Timestamp each call to IMAPISupport::OpenTemplateID.
3. Evaluate whether or not it is necessary to perform a full update based on the amount of time that has expired since the last call. If a full update is necessary, call IMAPISupport::OpenTemplateID with the FILL_ENTRY flag. If it is not necessary, do not set the flag on the call.

When a client makes a request for one of the copied recipient's properties, your provider can choose whether to handle the request itself or use the code supplied by the foreign provider. Your provider can expect the foreign provider to intercept most, if not all, calls to IMAPIProp except for IMAPIProp::OpenProperty. A call to OpenProperty requesting the PR_DETAILS_TABLE property is always forwarded to your provider.

To access template identifier code

1. Open the recipient and call its IMAPIProp::GetProps method to retrieve the PR_TEMPLATEID property. If GetProps fails because PR_TEMPLATEID is unavailable, the foreign provider does not support a template identifier and related code for this recipient. Your provider will need to use its implementation of the recipient for all maintenance.
2. If the template identifier is returned from GetProps, pass it and a pointer to the recipient's IMAPIProp implementation in a call to the IMAPISupport::OpenTemplateID method. Set the FILL_ENTRY flag if most or all of the recipient's properties need to be updated, such as at creation time or if they have not been updated for a while.
3. If OpenTemplateID returns the foreign provider's IMAPIProp implementation, return to the client a pointer to this implementation.
4. If OpenTemplateID does not return an implementation, typically because the foreign provider is not in the profile, return to the client a pointer to your provider's IMAPIProp implementation. The client should be able to work with the object's properties using either interface.