using System;

​

public class Program

{

    public static void Main()

    {

        String val = "iohexoL 350 mg iodine/mL solution (OMNIPAQUE) Ordered and Given: 175 mL Given Rate: 0 Route: intracoronary";

        var start = val.IndexOf("Ordered and Given:") + "Ordered and Given:".Length;

        var end = val.IndexOf("mL Given Rate:");

        Console.WriteLine(start + " " + end);

        var myValue = val.Substring(start, end - start).Trim();

        Console.WriteLine(myValue);

        Console.WriteLine(val[start..end].Trim());

    }

}