c# Code:
  1. //your SqlConnection here, name it conn
  2.  
  3. //SqlCommand
  4. Sqlcommand cmd = new SqlCommand();
  5. cmd.CommandText = "Select Count(studyIdNumber) from table_name WHERE studyIdNumber='FF12033'";
  6.  
  7. cmd.Connection = conn;
  8.  
  9. conn.Open();
  10.  
  11. int num_of_instance = cmd.ExecuteScalar();
  12.  
  13. conn.Close();
  14.  
  15. if (num_of_instance == 1)
  16. {
  17.      //Item already inserted
  18. }
  19. else
  20. {
  21.      //Insert new Item
  22. }
Hope it helps!!