Mappers are not applied when generating query WHERE clauses

[bryanboettcher]

For "legacy application" reasons our database primarily uses CHAR column types with a "Y" or "N" to represent boolean values. We created a BooleanMapper class that appropriately handles the conversion to and from the entity type and the database type.

Assume a table like this:

tbl_entities:
id  INT
enabled CHAR

If we query with: db.Query<TblEntities>().Where(e => e.Enabled), the generated SQL effectively becomes SELECT [id], [enabled] FROM tbl_entities WHERE enabled = 1. If the query were to succeed, the BooleanMapper we wrote will appropriately convert the dataset. But, because the enabled field is a char, the conversion to '1' fails during the query execution. If the query provider were aware of the registered mappers, the conversion to 'Y' could happen before the query is sent to the database provider.