Simulating ?. operator in C# 5

foo.cs

using System;

public static class ObjectHelpers {
	public static TResult WhenNotNull<T, TResult>(this T @object, Func<T,TResult> expression)
		//where T: class
		where TResult: class
	{
		if (@object == null)
			return null;
			
		return expression(@object);
	}
}

public static class StructHelpers {
	
	public static TResult? WhenNotNull<T,TResult>(this T @object, Func<T,TResult?> expression)
		//where T: class
		where TResult: struct
		
	{
		if (@object == null)
			return null;
			
		return expression(@object);
	}
}



public class ClassX {
	public ClassX Data { get; set; }	
	
	public override string ToString() {
		return "ok";	
	}
}

					
public class Program
{
	public static void Main()
	{
		Console.WriteLine("START");
		
		var data = new ClassX {
			Data = new ClassX {
				Data = null
			}
		};
		
		var foo = data
			.WhenNotNull(x => x.Data)
			//.WhenNotNull(x => x.Data)
			.WhenNotNull(x => x.ToString())
			.WhenNotNull(x => (int?)x.Length);
		
		Console.WriteLine(foo);
		
		Console.WriteLine("STOP");
	}
}