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 Finalizers in C#?

Short Answer:

Finalizers in C# (also called destructors) are special methods used to clean up unmanaged resources (like file handles or database connections) before an object is garbage collected. They are defined using the ~ClassName syntax and are automatically called by the garbage collector. However, they should be used sparingly due to their non-deterministic nature and potential performance overhead.

Detailed Explanation:

What are Finalizers?

Finalizers are methods in C# that allow you to perform cleanup operations on an object just before it is garbage collected. They are particularly useful for releasing unmanaged resources, such as file handles, database connections, or memory allocated outside the .NET runtime.

Syntax of Finalizers

A finalizer is defined using the tilde (~) symbol followed by the class name. It cannot have an access modifier, parameters, or a return type. Here’s an example: 


class MyClass
{
~MyClass()
{
	// Cleanup logic for unmanaged resources
}
}

When are Finalizers Called?

Finalizers are not called immediately when an object goes out of scope. Instead, they are invoked by the garbage collector (GC) during its cleanup process. This means you cannot predict exactly when a finalizer will run.

Why Use Finalizers?

Finalizers are primarily used to release unmanaged resources that an object might be holding. For example:

  • Closing file handles.
  • Releasing database connections.
  • Freeing memory allocated outside the .NET runtime.

Performance Overhead of Finalizers

Objects with finalizers require an additional round of garbage collection, which can introduce performance overhead. This is because the garbage collector must first call the finalizer before reclaiming the memory. To avoid this overhead, you can suppress finalization using GC.SuppressFinalize(this) when implementing the IDisposable pattern.

Finalizers and the IDisposable Pattern

In most cases, it’s better to use the IDisposable pattern along with a finalizer. The IDisposable interface allows you to explicitly release resources, while the finalizer acts as a safety net to ensure resources are cleaned up if Dispose is not called. 


class MyDisposableClass : IDisposable
{
    private bool disposed = false;

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this); // Suppress finalization
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!disposed)
        {
            if (disposing)
            {
                // Release managed resources
            }

            // Release unmanaged resources
            disposed = true;
        }
    }

    ~MyDisposableClass()
    {
        Dispose(false); // Finalizer calls Dispose for unmanaged resources
    }
}

Key Points to Remember

  • Finalizers are defined using the ~ClassName syntax.
  • They are automatically called by the garbage collector, but the timing is non-deterministic.
  • Finalizers are used to clean up unmanaged resources.
  • Objects with finalizers require an additional garbage collection pass, which can impact performance.
  • Use the IDisposable pattern for explicit resource cleanup and suppress finalization when possible.

When to Use Finalizers?

Finalizers should only be used when:

  • Your class holds unmanaged resources (e.g., file handles, database connections).
  • You need a safety net to ensure resources are released even if Dispose is not called.

When NOT to Use Finalizers?

Avoid using finalizers if:

  • Your class only uses managed resources (e.g., memory allocated by the .NET runtime).
  • You can reliably call Dispose to clean up resources.

Conclusion

Finalizers in C# provide a way to clean up unmanaged resources before an object is garbage collected. However, due to their non-deterministic nature and potential performance overhead, they should be used sparingly. In most cases, the IDisposable pattern is a better approach for resource cleanup. By understanding when and how to use finalizers, you can write more efficient and reliable C# code.

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