Downcasting in C#

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• J

  Jarrod15y agoPosted Feb 18, 2011, 4:37 PM

  But don't propagate bad code. Place a virtual Save() method on the Base Person class and have your Lawyer class override it to add its additional properties. public class Person { public string FirstName { get; set; } public string MiddleName { get; set; } public string LastName { get; set; } public int Age { get; set; } public virtual void Save() { Console.WriteLine("Name: " + mFirstName + " " + mMiddleName + " " + mLastName); Console.WriteLine("Age: " + mAge.ToString()); } } public class Lawyer : Person { public int NumberOfPeopleShafted { get; set; } public int NumberOfLiesTold { get; set; } public override void Save() { base.Save(); Console.WriteLine("Number of Clients Shafted: " + NumberOfPeopleShafted); Console.WriteLine("Number of Lies Told: " + NumberOfLiesTold); } } // Then you don't even need the PersonHandler class but just for grins: public static void SavePerson<T>(T pers) where T : Person { Type tPers = pers.GetType(); string[] arr = tPers.ToString().Split('.'); string personType = arr[arr.Length - 1]; switch (personType) { case "Person": Console.WriteLine("Save Type: " + personType); T.Save(); break; case "Lawyer": Console.WriteLine("Save Type: " + personType); T.Save(); } } Also, for dowcasting, don't do an explicit cast... use dynamic casting: Lawyer myLawyer = (MyPersonReference as Lawyer); if the cast fails then the myLawyer reference will be null.
• PR

  Peter Ritchie17y agoPosted Mar 2, 2009, 4:07 PM

  Polymorphism is the object-oriented method of doing this. You should have one method per case. You've got this use issue that the textual name you're comparing against is decoupled from the type name. If you changed the name of your type then you'd have runtime errors. Using polymorphism gets you compile-time checking. Not to mention, what method that gets called is decided upon compilation and no string comparison would be needed.
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    Scott Lysle17y agoPosted Mar 2, 2009, 9:20 PM

    It is if the architect does not require a single save method on the base class that handles all of the derived classes. I put this out there due to rather large and unresolved number of blog entries I encountered from people looking for a way to do exactly this. This is not preferred way of doing business and if it were it would not be prevented so naturally you are correct in what you've said, but if you don't have the luxury of being correct, this works.