Understanding C# Interfaces and Polymorphic Behavior by Dan Wahlin

Microsoft MVP Dan Wahlin shows how to use C# Interfaces with consistency to help developers. For the compete transcript of this video series, visit http://blogs.interfacett.com/?p=14590

In this session, I'm going to walk through one of the cool features of Interfaces, which is Polymorphic Behavior. Polymorphism is not only a big word you can impress friends and family with, it's actually really useful for what I call future-proofing your apps.

1. u c coskun: Amazingly simple and intuitive. Here is the first part: https://www.youtube.com/watch?v=jh4y8HzGqCQ
2. kishor rasure: what is the link for the previous session?
3. u c coskun: +kishor rasure Right below your comment. here is again. https://www.youtube.com/watch?v=jh4y8HzGqCQ
4. kishor rasure: +u c coskun where did you added link? Sorry I am not able to find it. If possible can you paste in comment? Thanks friend.
5. u c coskun: I have added the link. I think this is the only down side of this video... :)
6. Sanwal Chaudhry: he really knows how to teach programming concepts with real world problems.
7. Vicenzo Vendetta: A cat miaus, a dog barks, a monkey... ahahahahahaha
8. St S: Why to call Start() from another start(). Why can't we call the Start() directly as - car.Start(); mower.Start(); air.Start(); ? Also, in the first video, you said that Interface drives consistency across our program. But you didn't say anything about how that consistency helps. Please throw some light on these topics. Without these answers, my understanding of interfaces will not be complete.
9. u c coskun: Please watch the first part of this video. In the first part, he talks about training an employee how to start a machine. If you code like "car.start()" and "mower.start()", you need to train the employee two times: once for car and once for time for mower. In the future you need to teach him again for an airplane when it is implemented. On the other hand, if you use interfaces, you only ask him do "start()" procedure. You dont need to train him any more when another instrument is added. I hope this makes sense.
10. WillStar: truly elegant. I've only been programming two weeks and this makes perfect sense!
11. Conan Fortuna: You are a good teacher man, thank you very much.
12. Akram Al-Shameeri: finally, I have understood interfaces, I like them now, thanks.
13. Ratel: Have you just presented how Dependency Injection works?
14. Chris: I get it!! Thank you! If an infantry soldier can understand then you are a phenomenal teacher!
15. Theo Payne: I amm sooooo mind Blown, interfaces are Great O_O
16. Joe de Max: Didn't get interfaces at all until I watched this video. Thank you!
17. Microblitz: I had watched other explanations about interfaces and didnt really get it. Thanks for explaining it in such a clear and concise manner.
18. lostwhirley: THANK YOU SO MUCH !!! [ I now know Kung Fu - Neo (The Matrix) ] I struggled with the Interface concept and you helped me understand it ! Great examples !!!
19. George Vasquez: Excellent Example of Interfaces and Polymorphic Behaviors...Thanks
20. George Vasquez: Excellent example of Interfaces and Polymorphic behaviors...Thanks!
21. nishant singh: Futureproof- Nice Word Dan..It says it all... From what i know , Interfaces are useful only at those kinda projects where we have some providers like things....like some processing function which is done by different providers...and then we keep extending our new providers by implementing same interfaces...another trick comes when new provider also provides some other processing function that we also require to have...there we do versioning of Interfaces....Correct me If I Misunderstood... Thanks.
22. Sanford Hoffman: That was the most understandable explanation about the uses of an interface. Everyone says it's a "contract" but never has a practical example. Very simple and easy to follow. Good job. Thanks
23. Electronoob: Geeking Out: awesome
24. Orken1: By far the best explanation i've seen anywhere. Thank you, much appreciated
25. Rijden met Davey: THANK YOU SO MUCH. I've been struggling with this concept for a while because it can be pretty vague when not explained well. But just by watching and coding along now I understand it well.
26. Joker: thank you sir, best interface explanation!
27. coolandtall: Thank you. This is a tutorial.
28. Grant Williams: Two really helpful tutorials. The best explanation and examples I've yet seen that describe interfaces and polymorphism.
29. Bill Jennings: The best and most simple explanation I have seen!! I just watched 10 videos prior and it just didn't crystalize. Than Dan!!
30. Zhōu yǔ Qiáo: What a fantastic instructor! I wish Dan Wahlin had a full C# series!
31. Clovy Clov: He technically does, but it's $3000 lol
32. Steven Gauthier: Very clear explanation.... Better than a lot of 20 min videos...
33. troy bryant: Wow - two days of watching videos about abstract classes and interfaces and I come across this and in 7:11 not that I fully understand them but feel WAY more confident in the implementation
34. Marcel Ilders: Damn! That's maybe the single best explanation for the purpose of Interfaces I've come across so far. Thanks mate.
35. Nate L: I noticed that you instantiate your objects by writing var air = new airplain();  I have only seen people it this way airplain air = new airplain(); or something to that effect.  Is there some value to using "var" over the class name?Thanks for the help.  Love your videos
36. Nate L: Dan the man!
37. Anthony Sales: "Pass not as IMachine but as something that implements the IMachine"   --> my eureka moment!
38. Dani ESa: Best explanation of interfaces ever. Please go on for design patterns as you are a great teacher！Thank you so much.
39. yasayaninsan: By implementing an interface by different classes, you are defining a COMMON behaviour across these classes. You are grouping different classes in a same interface by means of a behaviour. By interface's point of view you are seeing different objects (polimorphism), but by looking from objects view you see a common direction towards the interface.
40. ehinola kingsley: Awesome.
41. KevinHarper3DArtist: Awesome, Thank you, very useful.
42. Aaron Gong: Awesome video. It really helped me to understand how Interfaces are useful in programming.
43. Junius01: I like your videos. They have a good structure, clear explanation and your language is easy to understand!
44. vinay tripathi: nice ,it good for me  ,thanks just like that  (thank=1;thank<=n;thank++)                                                                                   print("Thank");   n=infinite
45. Ghkjdf Hbjhffh: n should be declared above the for
46. l3ertuz: the only time I understood interfaces - big thanks!!!!
47. Michael Michuki: Dude...you have blown my mind..Literally, this my friend, is the best tutorial and explanation on interfaces , thanks :)
48. Josh Fredr: I wish you'd make a video course.. you are an amazing instructor that finally helped me understand interfaces with polymorphism. Thank you.
49. 3lysium1: I found this useful and the presentation was clear. Thanks
50. Mark Anderson: excellent example. had problems getting my head round it until now
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Understanding C# Interfaces and Polymorphic Behavior by Dan Wahlin
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Science & Technology	Upload TimePublished on 12 Aug 2013