Summary - Memory and GC

C# course · Expert · Lesson 6/47

Combine IDisposable, using and GC to write a resource pool.

Summary - Memory and GC

In this group you learned the GC generations (Gen 0/1/2), resource management with IDisposable, the using statement, GC.Collect and the LOH.

Combining these, you can write code that uses managed and unmanaged resources safely. Let's now build a small resource pool and a collection check.

Exercise Add Dispose to the Pool class

Define the Pool class with : IDisposable. In public void Dispose() write Console.WriteLine("Pool closed");. In Main use using var p = new Pool();.

Show example solution

IDisposable { public void Dispose() { Console.WriteLine("Pool closed"); } }. In Main: using var p = new Pool();
Example solution:
using System;

class Pool : IDisposable
{
    public void Dispose()
    {
        Console.WriteLine("Pool closed");
    }
}

class Program
{
    static void Main()
    {
        using var p = new Pool();
    }
}

Finalizer and dispose together

Remember: using works only when the type implements IDisposable. If the class has a finalizer and was disposed, calling GC.SuppressFinalize(this) cancels the finalizer and improves performance.

A well-designed class reclaims resources via the finalizer even if Dispose was forgotten. This is a safety net; still, calling Dispose explicitly is always preferred.

Exercise LOH array and collection

In Main allocate a LOH array with byte[] buf = new byte[100000];. Print Console.WriteLine("LOH allocated");. Then call GC.Collect(); and finally Console.WriteLine("Collected");.

Show example solution

Write byte[] buf = new byte[100000]; Console.WriteLine("LOH allocated"); GC.Collect(); Console.WriteLine("Collected");
Example solution:
using System;

class Program
{
    static void Main()
    {
        byte[] buf = new byte[100000];
        Console.WriteLine("LOH allocated");
        GC.Collect();
        Console.WriteLine("Collected");
    }
}

Test yourself

Which is an advantage of the using statement?
- Automatic Dispose at block end
- It speeds up the GC
- It resizes memory
- It creates threads
Show answer

Automatic Dispose at block end — Correct. using calls Dispose at block end.
Match the concepts

IDisposable

Dispose() method
using

Automatic Dispose
GC.Collect()

Force collection
LOH

~85 KB+ objects

All lessons in Expert

Summary - Memory and GC