using System;

using System.Collections.Specialized;                   

public class Program

{

    public static void Main()

    {

        NameValueCollection str=new NameValueCollection();         

        str.Add("test","test");

        //bool optOutOfMarketingMessages=(!string.IsNullOrEmpty(str["Body"]) && string.Equals("S", str["Body"].Trim(), StringComparison.OrdinalIgnoreCase));

        bool optOutOfMarketingMessages1 = (str["Body"]?.Trim().Equals("S", StringComparison.OrdinalIgnoreCase) == true);

​

        Console.WriteLine(optOutOfMarketingMessages1);

    }

}