Specifies the number of fields to use when conducting a partial key search on a multi-field key.
Use KeyFieldCount to limit a search based on a multi-field key to a consecutive sub-set of those fields. For example, if the primary key for a dataset consists of three-fields, a partial-key search can be conducted using only the first field in the key by setting KeyFieldCount to 1. If KeyFieldCount is 0, the dataset searches on all fields in the key.
Searches are only conducted based on consecutive key fields beginning with the first field in the key. For example if a key consists of three fields, an application can set KeyFieldCount to 1 to search on the first field, 2 to search on the first and second fields, or 3 to search on all fields. By default KeyFieldCount is initially set to include all fields in a search.