cast class into another class or convert class to another

What he wants to say is:

"If you have two classes which share most of the same properties you can cast an object from class a to class b and automatically make the system understand the assignment via the shared property names?"

Option 1: Use reflection

Disadvantage : It's gonna slow you down more than you think.

Option 2: Make one class derive from another, the first one with common properties and other an extension of that.

Disadvantage: Coupled! if your're doing that for two layers in your application then the two layers will be coupled!

Let there be:

class customer
{
    public string firstname { get; set; }
    public string lastname { get; set; }
    public int age { get; set; }
}
class employee
{
    public string firstname { get; set; }
    public int age { get; set; } 
}

Now here is an extension for Object type:

public static T Cast<T>(this Object myobj)
{
    Type objectType = myobj.GetType();
    Type target = typeof(T);
    var x = Activator.CreateInstance(target, false);
    var z = from source in objectType.GetMembers().ToList()
        where source.MemberType == MemberTypes.Property select source ;
    var d = from source in target.GetMembers().ToList()
        where source.MemberType == MemberTypes.Property select source;
    List<MemberInfo> members = d.Where(memberInfo => d.Select(c => c.Name)
       .ToList().Contains(memberInfo.Name)).ToList();
    PropertyInfo propertyInfo;
    object value;
    foreach (var memberInfo in members)
    {
        propertyInfo = typeof(T).GetProperty(memberInfo.Name);
        value = myobj.GetType().GetProperty(memberInfo.Name).GetValue(myobj,null);

        propertyInfo.SetValue(x,value,null);
    }   
    return (T)x;
}  

Now you use it like this:

static void Main(string[] args)
{
    var cus = new customer();
    cus.firstname = "John";
    cus.age = 3;
    employee emp =  cus.Cast<employee>();
}

Method cast checks common properties between two objects and does the assignment automatically.