Yes, you can extend existing types by using extension methods.

Can you extend the string class?

You cannot extend a class that is marked as final. You can use composition to either put a String object inside or you can hand roll your own version. This can be accomplished via character arrays and the other magic that goes into creating String classes.

What method extends the String class?

The String class is sealed so you can’t inherit from it. Extension methods are your best bet. They have the same feel as instance methods without the cost of inheritance. public static class Extensions { public static bool contains(this string source, bool ignoreCase) {… } }

Can extensions only extend static classes?

No. Extension methods require an instance of an object. You can however, write a static wrapper around the ConfigurationManager interface. If you implement the wrapper, you don’t need an extension method since you can just add the method directly.

Can we define extension method for a class?

An extension method is actually a special kind of static method defined in a static class. To define an extension method, first of all, define a static class. For example, we have created an IntExtensions class under the ExtensionMethods namespace in the following example.

Can we override string class methods?

You can’t override final classes, of which String is one. You can, though, create your own class with String helper functions. Show activity on this post. String is a final class and thus you can’t have another class extend it.

What is C# extension?

C# extension method is a static method of a static class, where the “this” modifier is applied to the first parameter. The type of the first parameter will be the type that is extended. Extension methods are only in scope when you explicitly import the namespace into your source code with a using directive.

Can we extend static class in C#?

NO, we can not inherit static class in c# because they are sealed and abstract. There seems to be no good reason to inherit a static class. It has public static members that you can always access via the class name itself. Any class which does not contain instance contructor, cannot be inherited.

Why extension methods are static?

Extension methods are static because they get the instance passed in via the first parameter, and they don’t act on the actual instance of their declaring class. Also, they’re just a syntactic sugar.

Can we inherit static class in C#?

Static classes are sealed and therefore cannot be inherited. They cannot inherit from any class except Object. Static classes cannot contain an instance constructor. However, they can contain a static constructor.

Can we inherit abstract class?

An abstract class cannot be inherited by structures. It can contains constructors or destructors. It can implement functions with non-Abstract methods.

Can a sealed class be static?

It can only have static members. It cannot have instance members as static class instance cannot be created. It is a sealed class. As static class is sealed, so no class can inherit from a static class.

Can static class have constructor?

A static class can only have static members — you cannot declare instance members (methods, variables, properties, etc.) in a static class. You can have a static constructor in a static class but you cannot have an instance constructor inside a static class.

Is Singleton a static class?

A Singleton can implement interfaces, inherit from other classes and allow inheritance. While a static class cannot inherit their instance members. So Singleton is more flexible than static classes and can maintain state. A Singleton can be initialized lazily or asynchronously and loaded automatically by the .

Can constructor be private?

Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.

Can abstract class have a constructor?

Like any other classes in Java, abstract classes can have constructors even when they are only called from their concrete subclasses.

Can we create object of interface?

Like abstract classes, interfaces cannot be used to create objects (in the example above, it is not possible to create an “Animal” object in the MyMainClass) Interface methods do not have a body – the body is provided by the “implement” class. On implementation of an interface, you must override all of its methods.

Can abstract class have private methods?

If a method of a class is private, you cannot access it outside the current class, not even from the child classes of it. But, incase of an abstract method, you cannot use it from the same class, you need to override it from subclass and use. Therefore, the abstract method cannot be private.

Can abstract class have static methods?

Yes, of course you can define the static method in abstract class. you can call that static method by using abstract class,or by using child class who extends the abstract class. Also you can able to call static method through child class instance/object.

Can we declare interface as final?

If you make an interface final, you cannot implement its methods which defies the very purpose of the interfaces. Therefore, you cannot make an interface final in Java. Still if you try to do so, a compile time exception is generated saying “illegal combination of modifiers − interface and final”.

Can we use public and abstract together?

Only public & abstract are permitted in combination to method. Example: public abstract void sum(); We use abstract keyword on method because Abstract methods do not specify a body.

Can a static method be final?

When a static method is overriden in a subclass it can still be accessed via the superclass making the final declaration not very necessary. Declaring a static method final does prevent subclasses from defining a static method with the same signature.

Can we execute class without main method?

Yes, we can execute a java program without a main method by using a static block. Static block in Java is a group of statements that gets executed only once when the class is loaded into the memory by Java ClassLoader, It is also known as a static initialization block.

Can we make a class abstract without an abstract method?

Yes, we can declare an abstract class with no abstract methods in Java. An abstract class means that hiding the implementation and showing the function definition to the user.