What is the difference between Finalize and Dispose in .NET?

Finalize is called by the garbage collector for cleanup, while Dispose is explicitly called to release unmanaged resources deterministically.

Which is preferred in modern .NET: Dispose or Finalize?

Dispose is preferred because it allows developers to clean up resources immediately and avoid relying on the garbage collector.

Use of Finalize vs Dispose in .NET | FullStackPrep.Dev

💡 Concept Name

Finalize vs Dispose in .NET

📘 Quick Intro

Both Finalize() and Dispose() are used for releasing unmanaged resources in .NET. Finalize is invoked by the GC, while Dispose is called explicitly by the developer.

🧠 Analogy / Short Story

Imagine leaving a hotel. You can leave your room and wait for the hotel staff to clean it (Finalize), or you can clean it yourself before leaving (Dispose). Dispose gives you control and avoids burdening housekeeping (GC).

🔧 Technical Explanation

Finalize() is a protected method automatically called by the garbage collector when an object is no longer reachable. You override it to clean unmanaged resources.

Dispose() is a public method from the IDisposable interface. It must be called manually (or via using) to free unmanaged resources deterministically.

🎯 Purpose & Use Case

✅ Use Dispose() for deterministic cleanup
✅ Use Finalize() only when Dispose isn't called
✅ Use both in combination via Dispose Pattern
✅ Always prefer using statement for IDisposable objects

💻 Real Code Example

public class FileManager : IDisposable
{
    private FileStream _stream;

    public FileManager(string path)
    {
        _stream = new FileStream(path, FileMode.Open);
    }

    public void Dispose()
    {
        _stream?.Dispose();
        GC.SuppressFinalize(this); // avoid finalizer call
    }

    ~FileManager()
    {
        Dispose();
    }
}

❓ Interview Q&A

Q1: What is Finalize() used for?
A: Cleanup of unmanaged resources during garbage collection.

Q2: What is Dispose() used for?
A: Manual cleanup of unmanaged resources.

Q3: Which one is deterministic — Finalize or Dispose?
A: Dispose.

Q4: What does GC.SuppressFinalize() do?
A: Prevents the Finalize call for an object.

Q5: Can we override Dispose()?
A: Yes, in classes implementing IDisposable.

Q6: When is Finalize called?
A: By GC before reclaiming memory.

Q7: What pattern uses both Finalize and Dispose?
A: Dispose Pattern.

Q8: Why prefer Dispose over Finalize?
A: For performance and control.

Q9: Should Dispose call GC.SuppressFinalize?
A: Yes, if Finalize is also implemented.

Q10: Can we use using() with Finalize?
A: No, only with IDisposable/Dispose.

📝 MCQs

Q1. Which method is called by the garbage collector?

Dispose
Free
Release
Finalize

Q2. Which method must be called manually?

Finalize
Collect
Dispose
CleanUp

Q3. What interface must a class implement to support Dispose()?

IGC
IReleasable
IDisposable
IManualCleanup

Q4. Which method is deterministic?

Finalize
Dispose
Both
None

Q5. Which method is safe to use in using() block?

Dispose
Finalize
Close
Abort

Q6. What does GC.SuppressFinalize() do?

Forces GC
Delays finalizer
Prevents GC from calling Finalize
Removes IDisposable

Q7. When should Finalize() be used?

Always
Never
Only with IDisposable
When unmanaged resources need fallback cleanup

Q8. What is the best practice for unmanaged resources?

Only Finalize
Only Dispose
No cleanup needed
Implement Dispose and optionally Finalize

Q9. Is Dispose() called automatically?

Yes
No
Only with GC
Only on crash

Q10. Which causes a performance hit if not suppressed?

Dispose
using()
GC.Collect()
Finalize

💡 Bonus Insight

Use the using statement with all IDisposable objects like FileStream, SqlConnection, etc., to ensure automatic and reliable cleanup. This is safer and more performant than relying on Finalize.

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Use of Finalize vs Dispose in .NET