Best way in ASP.NET of configuring rows in a database to delete after a certain time

Suppose I have a table in my database like

                           Registrants
=======================================================================
  id |    name    |            email        |    registration_date
=======================================================================
  1  |   "Sam"    | "sammypie49@gmail.com"  |    "2016-03-26T14:25:10"
-----------------------------------------------------------------------
  2  |   "Bob"    | "bthebuilder@msn.com"   |    "2015-12-01T10:09:30"
-----------------------------------------------------------------------
  .  |     .      |           .             |              .
-----------------------------------------------------------------------
  .  |     .      |           .             |              .
-----------------------------------------------------------------------
  .  |     .      |           .             |              .
-----------------------------------------------------------------------
  .  |     .      |           .             |              .

and I want every registrant to automatically be deleted, say, 100 days after registering. What is a proper way to do this, and what is the best way?

The shoddy way I was planning on doing it was going to be to create a sproc

CREATE PROCEDURE FlushOldRegistrants
AS
BEGIN
   DELETE FROM Registrants WHERE DATEADD(day,100,registration_date) < GETDATE()
END

and in my server-side code invoke that sproc every once in a while like

Script.SetInterval(delegate {
    using (var conn = new SqlConnection(connectionString))
using (var command = new SqlCommand("FlushOldRegistrants", conn) { 
                           CommandType = CommandType.StoredProcedure }) {
   conn.Open();
   command.ExecuteNonQuery();
   conn.Close();
}
 }, 60000); // flush old registrants every hour

But, can I do that all at the database level? Is it possible to create a T-SQL TRIGGER that does this? Or is there an even better way?