One of the possible approaches:
1. Write a stored procedure (plain SQL would be harder) that will return a table with two fields (day, exists).
- The input parameters need to be the starting date, the number of days to be checked and maybe other conditions (filtering only selected resources, etc.).
- The best way would probably to create a loop that runs SELECT command for each day to determine whether there is an event.
- Output data source will contain two fields: day (date) and exists (bool).
2. Store the SP result in a DataTable (dt) with a PrimaryKey defined as "day" field.
3. In the isThereEvent method, check the DataRow returned by dt.Rows.Find(targetDateTime) for "exists" field.