What is a Destructor in C#?
💡 Concept: Destructor
A destructor is a special method in C# that is automatically invoked when an object is being garbage collected. It is used to clean up unmanaged resources before the object is destroyed.
📘 Quick Intro
In C#, destructors are defined using a tilde (~) followed by the class name. They do not take parameters, cannot be overloaded, and are called by the garbage collector just before object destruction.
🧠 Analogy
Imagine you’ve stayed at a hotel. Before leaving, you tidy the room, switch off the lights, and return the key. A destructor works the same way—cleaning up before an object “checks out” of memory.
🔧 Technical Explanation
- Destructors are parameterless and have no return type.
- They are called automatically by the garbage collector.
- They are mainly used to release unmanaged resources.
- You cannot control the exact time of destructor execution.
- They are not commonly needed in C# due to IDisposable and using statements.
🎯 Use Cases
- To release unmanaged resources like file handles, sockets, or database connections.
- To log finalization or object cleanup for debugging.
- Rarely used in modern C# when IDisposable is preferred.
💻 Code Example
public class FileManager
{
private FileStream fileStream;
public FileManager(string path)
{
fileStream = new FileStream(path, FileMode.OpenOrCreate);
}
~FileManager()
{
// Destructor
fileStream?.Dispose();
Console.WriteLine("Destructor called, resources released.");
}
}
❓ Interview Q&A
Q1: What is a destructor in C#?
A: A method called by the garbage collector before the object is destroyed.
Q2: When is a destructor executed?
A: During garbage collection, not immediately after object goes out of scope.
Q3: Can destructors be overloaded in C#?
A: No, they must not have parameters and cannot be overloaded.
Q4: Can we call a destructor explicitly?
A: No, only the GC calls it automatically.
Q5: What is the syntax for declaring a destructor?
A: ~ClassName().
Q6: Do destructors guarantee timely resource cleanup?
A: No, timing depends on GC.
Q7: Is IDisposable better than destructors?
A: Yes, it gives more control over cleanup timing.
Q8: Do structs have destructors?
A: No, only classes support destructors.
Q9: What’s the risk of relying on destructors?
A: Uncertain timing and potential memory/resource leaks.
Q10: What is the relationship between finalizers and destructors?
A: Destructors are compiled into finalizers in IL code.
📝 MCQs
Q1. What is the purpose of a destructor in C#?
- Initialize objects
- Invoke constructors
- Clean up unmanaged resources
- Handle exceptions
Q2. How is a destructor defined?
- Destructor()
- ~ClassName()
- void Destructor()
- finalizer()
Q3. When is a destructor called?
- On object creation
- On method call
- When object is garbage collected
- During compilation
Q4. Can destructors be overloaded?
- Yes
- No
- Only in sealed classes
- Only with parameters
Q5. Do destructors take parameters?
- Yes
- No
- Only ref parameters
- Only out parameters
Q6. Can destructors be static?
- Yes
- No
- Only in abstract classes
- Only with IDisposable
Q7. What happens if you forget to dispose resources and don’t use a destructor?
- Nothing
- Memory leak may occur
- Program crashes
- Compiler error
Q8. Can destructors be explicitly invoked?
- Yes
- No
- Only once
- With special syntax
Q9. What is the IL equivalent of destructor?
- Constructor
- Interface
- Finalizer
- Static block
Q10. Which interface provides deterministic disposal of resources?
- IClonable
- IDisposable
- IEnumerable
- IFinalizable
💡 Bonus Insight
Use destructors only when necessary. Prefer the IDisposable interface for better control and reliability. The garbage collector is non-deterministic, and relying on destructors alone can lead to subtle bugs or performance issues.
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