That's not possible. but you can use an Object Mapper like AutoMapper
Example:
class A
{
public int IntProp { get; set; }
}
class B
{
public int IntProp { get; set; }
public string StrProp { get; set; }
}
In global.asax or application startup:
AutoMapper.Mapper.CreateMap<A, B>();
Usage:
var b = AutoMapper.Mapper.Map<B>(a);
It's easily configurable via a fluent API.