Database

SELECT *
FROM Applicant 
WHERE date_of_death is null
   OR date_of_death>@somedate

SELECT
    id_Applicant,
    name,
    date_of_birth,
    date_of_death
FROM
    Applicant
WHERE
    '5/30/2012' BETWEEN date_of_birth AND ISNULL(date_of_death,'1/1/3000')

SET DATEFORMAT DMY

using (var con = new SqlConnection(connectionString))
using (var cmd = con.CreateCommand())
{
  cmd.CommandText = "SELECT * FROM SomeTable WHERE MyDate = @MyDate";
  cmd.Parameters.AddWithValue("@MyDate", DateTime.Now);
}

Bastard Programmer from Hell

CREATE FUNCTION [dbo].[Function_Name] (@inputParameter int) RETURNS table AS Return (<select clause> <from clause> WHERE <filterFieldName> = @inputParameter [<group by clause>])