How to check whether the record exists or not in the database while inserting new record using C#?

 public bool checkRecordExistsOrNot(string login)
    {
        string ConnString = GetConnString();
        string sqlString = "SELECT yourtablename.yourcolumnname FROM yourtablename WHERE yourcolumnname= ?";
        using (OleDbConnection conn = new OleDbConnection(ConnString))
        {
            using (OleDbCommand cmd = new OleDbCommand(sqlString, conn))
            {
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.Add("?yourcolumnname", OleDbType.VarChar).Value = login;
                conn.Open();
                if (cmd.ExecuteScalar() != null)
                {
                    conn.Close();
                    conn.Dispose();
                    return true;
                }
                else
                {
                    conn.Close();
                    conn.Dispose();
                    return false;
                }
            }
        }
    }

  public static string GetConnString()
    {
       return ConfigurationManager.AppSettings["ConnectionString"].ToString();
    }