.NET Fiddle

CSharp · Console

/Program.cs

using System;
using AutoMapper;
					
public class Program
{
	public static void Main()
	{
		var a = new A { Foo = 9, MyEnum = MyEnum.Alert};
		var b = new B();
		Mapper.CreateMap<A, B>().ForMember(dest => dest.Bar, opt => opt.MapFrom(src => src.Foo.HasValue ? src.Foo.Value.ToString() : string.Empty)).ForMember(dest => dest.MyEnumString, opt => opt.MapFrom(src => src.MyEnum.HasValue ? src.MyEnum.Value.ToString() : string.Empty));
		Mapper.AssertConfigurationIsValid();
		Mapper.Map(a, b);
		Console.WriteLine(b.Bar);
		Console.WriteLine(b.MyEnumString);
		a = new A { Foo = null, MyEnum = null };
		Mapper.Map(a, b);
		Console.WriteLine(b.Bar);
		Console.WriteLine(b.MyEnumString);
	}	
}

public class A 
{
	public int? Foo { get; set; }
	public MyEnum? MyEnum { get; set; }
}

public class B
{
	public string Bar { get; set; }
	public string MyEnumString { get; set; }
}

public enum MyEnum 
{
	Alert = 1,
	Other = 2,
	Etc = 3
}