static void Main(string[] args)
{
    FbConnectionStringBuilder connStrBuilder = new FbConnectionStringBuilder();
    connStrBuilder.Database = "localhost/3051:horses";
    connStrBuilder.UserID = "SYSDBA";
    connStrBuilder.Password = "masterkey";
    connStrBuilder.Charset = "WIN1251";
    using (FbConnection conn = new FbConnection(connStrBuilder.ToString()))
    {
        string sql = "SELECT CODE_HORSE, REMARK FROM HORSE WHERE REMARK IS NOT NULL FETCH FIRST 10 ROWS ONLY";
        conn.Open();
        FbCommand selectCommand = new FbCommand(sql, conn);
        FbDataReader reader = selectCommand.ExecuteReader();

        if (reader.HasRows)
        {
            while (reader.Read())
            {
                Console.WriteLine("{0}\t{1}", reader["CODE_HORSE"], reader["REMARK"]);
            }
        }
        else
        {
            Console.WriteLine("No rows found.");
        }
        reader.Close();

        Console.ReadLine();
    }
}

REMARK BLOB SUB_TYPE TEXT

SELECT CAST(RDB$PROCEDURE_BLR AS BLOB SUB_TYPE TEXT) AS TXT
FROM RDB$PROCEDURES P