using System;

​

public class Program

{

    public static void Main()

    {

        var foo = new Foo();

        foo.Total += 7;

        Console.WriteLine(foo.Total?.ToString() ?? "OMG");

        var bar = new Bar();

        bar.Total += 7;

        Console.WriteLine(bar.Total?.ToString() ?? "WTF");

    }

​

    public class Foo

    {

        public decimal? Total { get; set; }

    }

    public class Bar

    {

        public decimal? Total { get; set; } = 7m;

    }

}