OOP (object oriented programming)What is the class?What do you mean by object?What are the differences between class and object?Can you create an object without using new operator in C#?What is constructor and how many constructors can have one class?Differences between constructor and method of the class? What is default constructor?What is parameterized Constructor in C#?What is private constructor: In what instances you will declare a constructor to be private?What is static constructor, Is it possible to have a static constructor in class. If yes why we need to have a static constructor?Does C# provide copy constructor for an object? How do you call the multiple constructors of a class with single object creation?What is constructor chaining in C#?Can a constructor be called directly from a method?What is constructor overloading and how it’s different than method overloading?What is the difference between constructor overloading and method overloading?Is it possible to overload copy constructor in C#?Can we overload static constructors in C#?Can we overload private constructors in C#?Can we give return type of the constructor in C#?What is the destructor and when it’s called?Is it possible to call constructor and destructor explicitly?What is the Structure and why we need it although we have a class?What are the similarities between Class and Structure?What is the difference between Class and Structure?What is copy structure?What is nested structure?Is it always necessary to create an object of the class?How many different ways to create an object of the class?What are the pros and cons of creating object by new() keyword?What are the pros and cons of delegate object creation to DI container?What are the pros and cons of creating an object by reflection?What are the pros and cons of getting an object from an object pool?What are the pros and cons of creating an object by deserialization?Is it possible to create an object without a class in C#?What is constant?What is static modifier? What are the Static fields and methodsWhat is Static ReadOnly?What are the limitations of static?What is readonly? What’s the difference between constant and read-only?What is this keyword?What is base keyword?What is the difference between this and base keyword?Can “this” keyword be used within static method?What are the accessors?What is the static class? Why we need of static class?If someone wants to create static class then what are the rules for the static class?What are the limitations of using static keyword?What are finalizers in c#?How to create N number of instances of C# class?What are the Nested Classes and why we use them?What are the basic four pillars of OOP?What is the Inheritance and why we need of inheritance?How do you inherit a class into other class in C#?What is the concept of base and derive class?What are the different types of inheritance?We have two classes’ base class and child class. A is the base class and B is the child class, If we create an instance of child class then which class’s constructor called first?Does a derived class can inherit the constructors of its base class?What should we do that if we create an object of child class then the parameterized constructor of base class must be invoked?As we know that base constructor invoked first when we create instance of child class but if we create an instance of child class by parameterized constructor and base class has both default and parameterized constructor then which constructor of the base will be invoked?Can you assign an object of derived class to the variable of base class and if both have the same method name then which will be invoked?Can we create instance of base class and store it to derive class?Can we create derive class object inside base class, and if create instance of child class then what will happen?Can we inherit child class from 2 base classes? if yes then how? If not then why?Does C# support Multiple Inheritance?Why multiple inheritance is not supported in C# and why it’s supported in C++?How is multiple inheritance achieved in C#?What are Access Modifiers? Explain private, public, protected, internal, protected internal access modifiersWhat are the default access modifiers of the class?Why classes cannot be declared as protected?Can we declare private class in namespace?What are the valid access specifier used for the declaration of class at namespace level? If we inherit a class, do the private variables also get inherited?Can you prevent your class from being inherited?Can you prevent your class from being inherited without using sealed keyword?What is abstraction?What is encapsulation?What is the difference between abstraction and encapsulation?What is polymorphism?What is static or compile time polymorphism?What is runtime polymorphism or late binding or dynamic binding?What is method overloading?When and why we should use overload methods?What is inheritance based overloading?What are the advantages of using overloading?Can we overload the method in the same class?What is the execution control flow in overloaded methods?What is method overriding?What s virtual keyword?What are the key points to make the method as overridden?When it is must to override the method?When a derived class can overrides the base class member?Can we declare fields inside the class as virtual?When we treat sub-class method as an overriding method?Can we override private virtual method in c#?Can we override method in the same class?Can we execute parent class method if it is overridden in the child class?If we have virtual in base class and the same method is overridden in child class, by creating instance of child class and assign it to base class, then which of the method will be invoked first.What is the difference between method overloading and method overriding?What is method hiding?Can you access a hidden method in the derived which is declared in the base class?What is the difference between method overriding and method hiding?You have a component with 2 parameters and deployed to client side, now you have changed your method with 3 parameters, how can you deploy this without affecting the client code?What is operator overloading?What is abstract class and why we need of it?What are the rules of abstract classes?What is an abstract method?What is concrete method?When do you use abstract class in C#?When to use the abstract method in C#?
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What Are the Default Access Modifiers of the Class?

Short Answer

In C#, the default access modifier for a class is internal, meaning it is accessible only within the same assembly. For methods, properties, and variables within a class, the default access modifier is private, meaning they are accessible only within the same class.

Detailed Explanation with Examples

Access modifiers in C# control the visibility and accessibility of classes, methods, properties, and variables. If you don’t explicitly specify an access modifier, C# assigns a default one. Let’s break this down for classes, methods, properties, and variables.

1. Default Access Modifier for Classes

By default, a class in C# has an internal access modifier. This means the class is accessible only within the same assembly (a compiled unit of code, like a DLL or EXE). It cannot be accessed from outside the assembly.

Example of a Default Internal Class


class MyClass
{
    // Class members and implementation
}

In this example, MyClass is implicitly internal because no access modifier is specified. It can be accessed by other types within the same assembly but not from outside.

Making a Class Accessible Outside the Assembly

To make a class accessible from outside its assembly, you need to explicitly use the public or protected internal access modifier.

Public Access Modifier

public class MyClass
{
    // Class members and methods
}

Here, MyClass is marked as public, making it accessible from anywhere, including other assemblies.

Protected Internal Access Modifier

protected internal class MyClass
{
    // Class members and methods
}

This allows MyClass to be accessed within its assembly and by derived classes in other assemblies.

2. Default Access Modifier for Methods and Properties

The default access modifier for methods and properties is private. This means they are accessible only within the same class and not from outside.

Example of Default Private Methods and Properties


public class MyClass
{
    // Private method (default access)
    void MyMethod()
    {
        Console.WriteLine("This is a private method.");
    }

    // Private property (default access)
    int MyProperty { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        MyClass myObject = new MyClass();
        // myObject.MyMethod(); // Error: Cannot access private method
        // myObject.MyProperty = 42; // Error: Cannot access private property
    }
}

In this example, MyMethod and MyProperty are implicitly private because no access modifier is specified. They can only be accessed within MyClass.

Making Methods and Properties Accessible Outside the Class

To make methods and properties accessible from outside the class, use the public access modifier.


public class MyClass
{
    // Public method
    public void MyMethod()
    {
        Console.WriteLine("This is a public method.");
    }

    // Public property
    public int MyProperty { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        MyClass myObject = new MyClass();
        myObject.MyMethod(); // Accessible
        myObject.MyProperty = 42; // Accessible
    }
}

3. Default Access Modifier for Variables (Fields)

The default access modifier for variables (fields) is also private. This means they are accessible only within the same class.

Example of Default Private Variables


public class MyClass
{
    // Private field (default access)
    int privateField;

    public void SetPrivateField(int value)
    {
        privateField = value;
    }

    public int GetPrivateField()
    {
        return privateField;
    }
}

class Program
{
    static void Main(string[] args)
    {
        MyClass myObject = new MyClass();
        // myObject.privateField = 42; // Error: Cannot access private field
        myObject.SetPrivateField(42); // Accessible through public method
        Console.WriteLine(myObject.GetPrivateField()); // Accessible through public method
    }
}

Here, privateField is implicitly private and can only be accessed within MyClass. To access it from outside, you need to use public methods like SetPrivateField and GetPrivateField.

Key Points to Remember

  • Class: Default access modifier is internal.
  • Methods, Properties, and Variables: Default access modifier is private.
  • Encapsulation: Use access modifiers to control visibility and maintain encapsulation.

Conclusion

Understanding default access modifiers in C# is crucial for writing secure and maintainable code. By default, classes are internal, and methods, properties, and variables are private. You can change these defaults using access modifiers like public, protected, or protected internal based on your design needs.

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