Part 56 C# Tutorial Generics in C#

hello welcome to prism technologies i'm venket this is part 56 generics in this session we'll understand the basics of generics and the advantages of using generics now general exit introduced in c-sharp 2.0 generics basically allow us to design classes and methods decoupled from the data types which will allow our code to be reused with any data type let's understand what we mean by this with an example now here you can see a very simple calculator class which has got an R equal method and if you look at this method it's very simple all it's doing is it's taking in two values of type integer comparing those two if they're equal it returns true otherwise it returns false now let's see how to use this method let's say boolean equal is equal to since the method is a static method I can just use the name of the class instead of creating an instance of that let's say for example if I pass 1 comma 2 they are not equal and then if equal we want to say the numbers are equal otherwise not equal very simple code if we run this obviously since these are not equal it will print not equal that's fine but then the issue here is if you look at this calculator class and this are equal method now this are equal method is actually tied to the data type now let's say the user wants to compare two strings if they are equal or the user wants to compare two characters if they are equal now can he use this method he cannot because this method only works with integer data type so your method is basically now tightly coupled with the data type that it operates on okay so if I make this method let say for example I want to compare two strings maybe a and B look at at the moment I do that you already have a red squiggly there indicating a compiler error okay so obviously the error message it makes sense the best overloaded method for calculated are equal intercom I ain't has some invalid arguments so it's expecting integer arguments but you're passing string arguments into this method so obviously it doesn't compile so how do I make this method operate on any data type because you know the logic is pretty simple if they're equal written true otherwise returns false so it need not be tied to any type okay so how can I do that one way to make this method operate on any data type is just replace this integer with object data type okay the moment we do that look at that the error goes away and look at this this is a and B they're not equal if I run this obviously it will say not equal but on the other hand just to make sure it's working as expected and they I run this okay they are equal so now if you look at this this method is reusable with any type it's not now tied to any type but the problem here is you know and why have we in the first place how are we able to do this if I convert the data type from integer to object then I'm able to pass strings I'm able to pass integers how is that possible you know we know that within dotnet framework every type directly or indirectly inherits from system to object so obviously you can you know since string the integer you know any type you take for that matter you know directly or indirectly it inherits from system object so you can pass the type as an inherited type into this method that's how it works but then the problem with this there are two issues with this way of coding one is let's say for example if I pass 10 and 10 integers now when I actually run this program at runtime what's going to happen is this 10 we know integer is a structure which means it's a value type so at runtime this value type needs to be converted into object type you know object is nothing but a class look at that the intellisense class system to object but but whereas integer is actually a structure a value type so at runtime this value type needs to be converted into reference which is nothing but your class so converting value types to reference types is called as boxing so boxing is happening unnecessarily here just for the purposes of comparison okay so because of this unnecessary boxing and unboxing what's going to happen is the performance is going to be degraded that's one problem another problem with this method look at this now if somebody is calling this method okay now the reason why they call this method is to determine if two values of the same type are equal or different for example I want to compare it to integers are equal or if two strings are equal or if two characters are equal but since now you made this type of object you know users can say okay I want to compare if 10 is equal to a B now this doesn't make sense you shouldn't be allowing that in the first place but here our code will happily compile because what is the type that we are dependent upon object type so you will be able to pass in anything for the first parameter and anything for the second parameter okay so now this method is no longer strongly typed we lost that you know we lost the strongly type nature of this method number one and number two because of boxing and unboxing there is performance recreation so to solve both of these problems we can actually make use of generics okay so the best way to make this method independent of the data type is to use generics let's see how to do that so obviously you know we don't want to be doing stuff like this let's say I want to compare a B with a B and determine if they are equal okay so let's see how to correct that so now instead of object type what I can basically do seeds using generics is very simple okay all you have to do is put an angle bracket C I want to make this method generic now generic meaning I want to make this method independent of the type it operates upon okay so what I'm doing here is I'm going to say some type I don't know about the type okay and the parameter that the user is going to pass M is going to be of this type T okay so what is this T we don't know it could be integer string enum whatever it will only be known by the calling client okay when somebody calls this method that's when they specify on what type they want this method to operate on and then here we have to do a slight change because this is a type you cannot directly compare them like this instead you have to use the equals method which system that object provides to every type within the ordinal framework okay so T I mean we know that one is value one the other one is value two and both of type T okay so f value 1 dot equals value 2 okay return value 1 dot equals value 2 if they are equal it will return true otherwise it's going to return false now look at this there is no hard-coded logic here you know we are not telling on which type this method is going to operate upon all right now if you look at this one now what you need to do here is basically specify the type now let's say I want this method now to operate on the string type look at that the moment you do that the moment you specify look at this 4 are equal you are saying the type is going to be string so obviously for this T it's going to be string which means value 1 and value to both of them have to be strings but if somebody tries to compare integers and strings let's say if somebody tries to do that we immediately get an invalid arguments compiler error because it's expecting string comma string but you are trying to pass an integer and string which will not be a lab so we got that strongly typed in nature back ok that's one thing and here boxing and unboxing will never happen let's say for example if I want to compare two integers okay now then the moment I open this look at that ok now it's going to operate upon integers it's not system don't object individual is a value type is going to stay value type during that comparison it's not going to be converted back and do you know a reference type box it will not happen so we got that performance gain as well so now let's say I want to compare 10 comma 10 which are equal if we run this obviously they are equal so now your code is actually type independent so generics are nothing but this okay generics make your code type independent and that way you can reuse your code with any type and obviously when you use generics you know you get that strongly type nature number one and you also have that performance gain from unnecessary boxing and unnecessary you know unboxing okay generics actually are extensively used with the collection classes that are present in systems or collections for generic namespace you know which will be which will actually be talking about in the next session all right now if you look at this one here we made this method generic okay it's also possible to make classes generic instead of saying okay I want this method to operate on any type you can say this class basically can operate on any type which means all the methods in this class are going to in a way operate on that type for example instead of specifying this T here what you can do is you can specify that T for the class itself so now you're making the class generic so instead of specifying the type here you specify that on the class maybe I want this class to operate on the nth data type okay the moment you do that here look at that this method is when I expect into your data types look at the intellisense all right so now if we run as you might expect the output will still be the same except that in this case we made this class generic in a previous example we made this method generate okay along the same lines you can also make interfaces generate delegates generate so let's go back to the slides so obviously generates that extensively use recollection classes available in the generics namespace which we'll be talking about in the next session and we have seen one way of making the are equal method you know basically operate on anytime is to use the system load object type but what are the disadvantages of using so your are equal method is no longer type safe and performance digression degradation due to boxing and unboxing and obviously the best way to make a class or a method or an interface you know operate on any data type is basically to use generics using that specific type T now you might be wondering does it have to be T always now you can give it any meaningful name you want because you know here it since it's a type that we are talking about it makes sense or I specify the T generally the naming convention is to use T but you can of course give it any name that you want all right so on this slide you can find some resources phrase without net and c-sharp interview questions that's it for today thank you for listening have a great day

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Keywords: Generics in C#, why do we need generics in c#, c# generic methods, c# generic method example, c#.net generics example, c# generic vs non generic method, convert non generic method to generic method c#

Id: -zHRmXkJ5Bw

Length: 12min 1sec (721 seconds)

Published: Wed Jul 11 2012