In what scenario we need to create Static Class?

Question

Interview question-: Why we need to create a Static Class, why shouldn't we create a normal class instead of that. Real world example to explain.

Tapan Patel · Answer

As I mentioned in my answer on this link, it is required when we want the specific type of task to be done by same object multiple time (just one example). http://www.c-sharpcorner.com/forums/public-static-classname-obj-new-classname Another example would be, sending emails using SMTP server. You shouldn't create separate object for sending the email application (with different forms/web pages). Instead create static class that takes string as message body and To Address as parameters and sends the email using appropriate SMTP server. Doing that, not only you save memory (considering object creation) but also your code tends to follow the design pattern and it will be more organized.

Tapan Patel · Answer

Consider the example of TFS Work Items management using C# programming. I mean through code. If you have a requirement to write a classes (separate classes ) that deals with TFS User Story, TFS Bugs, TFS Project, think something that is common in all above classes and you will have to do no wonder what to deal with TFS items. Connection to TFS Work Items. Also, reading the any of the work item from TFS is a common Task. So , you can define the Abstract class which has implementation of Connecting to TFS Server, and it also has implementation of Reading the work item of type you can pass as parameter. Let’s say the method is : List ReadTFSItem(string ItemType, int ItemNumber) . And this method return the Title and Description of the work item. So every class that is sub-classing this Abstract class gets the advantage of this methods and if there is requirement to read certain more attributes from TFS, then this child class can always Override the methods of abstract class and write their own implementation of reading extra fields like History of that work item or stack rank or any other.

Tapan Patel · Answer

You need interface when you want to have certain methods (with specific return type or taking certain parameters) to be implemented by each class which is implementing it. Although the implementation can be different.Having concrete model gives you advantage. Take an example of Sending email using SMTP Server on large scale application. You can define the method int SendEmail (string body, string ToAddress) as interface. Now assume that this interface is being implemented by different classes. Users can configure the SMTP Servers for google or yahoo or MSExchange. Now all of them may require certain implementation on their own but all they need to do is to use Send method with defined syntax. This method will be different in all three classes (as per the requirement) This way, You achieve the thorough implementation of your model across different classes.

Tapan Patel · Answer

Please check my answer at http://www.c-sharpcorner.com/forums/public-static-classname-obj-new-classname Please mark it as answer if it addresses the issue.

Nitin Sontakke · Answer

Let me add something more to the static class. You will need a bit of patience understand the following. Take time to read it carefully. Before .NET, not being fully object oriented, there were loads of mathematical functions floating everywhere in VB 6. In .NET, if you notice carefully, there are pretty much no free floating function at all. All functions are part of the class. For example, Sqr for Square root. Now there are several such functions which need to be clubbed in to a class. In entire universe there is only one mathematics, for example, everywhere the square root of 9 is 3. But we want to create a class which will have a function square root. Now imagine a normal class created as a Math. But what different functionality each instance of such a class can offer? Absolutely NOTHING! Each execution of square root is going to return same value when a specific value is passed as a parameter (FYI: this is also called a deterministic function). That's why you create a Math class which is static because creating an instance of this class is illogical. Hope you understand.

Tapan Patel · Answer

No problem. You are welcome. And shoot me the question if you have any. Please mark the best as an answer if you are satisfied.

Anil Thakur · Answer

Thanks man, that was really helpfull, i have some more questions i will come with those ;)

Anil Thakur · Answer

whaw man, that's very nice example of an Interface, could you give for an Abstract Class?

Anil Thakur · Answer

One more question, why we need to create an interface when we can't define the method in that, when we actually define it in the class then what is the use to create an interface?

Tapan Patel · Answer

Probably this would help. http://www.c-sharpcorner.com/UploadFile/hirendra_singh/static-classes-in-C-Sharp/

Anil Thakur · Answer

Thanks Man, but still the question i asked not clear to me.

Tapan Patel · Answer

okay, so Class types which cannot be instantiated are either abstract class ( and interface which is not a class but still used to model the concept). Abstract classes cannot be instantiated and are used to inherit the functionality it has by inheriting the class and implement the stuff the way you want and (if you want). These classes contain the some generic code that can be used or modified by derived class. Where as Interface just gives you modeling structure, you need to implement the way you want. (it is mandatory to implement the methods if you are implementing the interface). On the other hand, static classes are used to store the bunch of code which works the way it is coded, You need not worry about changing it throughout your application. For detailed information please refer below link. http://stackoverflow.com/questions/5665691/abstract-classes-vs-static-classes-in-c-sharp

Anil Thakur · Answer

So you could tell me why we need to create a class which doesn't allow to create object, how that can help us.

Tapan Patel · Answer

You are right. Having static class allows you to access functions/methods directly using the syntax as ClassName.StaticMethod name. it basically allows you to write utility sort of things where you define generic operations which are likely to be changed over the time.

Anil Thakur · Answer

Hello Tapan, So just for not to make an object of class we should use Static Class, and to make code more organized, that's it, that is the reason we should create static class? I am so confused in this question, if we have any other reason for this or any other example you can share please share.

Anil Thakur · Answer

Thank You for the reply, but i know the basic answer of this question, but my question is why we need to create a static class in our project?

Midhun Tp · Answer

Hi, We can access methods in static class without creating an instance of that class. Static class can have only static members. An simple example of static class - static class Perls { public static int _value=5; } class Program { static void Main() { Console.WriteLine(++Perls._value); } } The output will be 6.