GC.Collect in C#

Question

Hello,

I expected to see "I'm Destructor..." message in the following code because GC ran.
Could you please explain why the desctutor didn't run when I called GC.Collect explicitly?

using System;  
  
internal class Program  
{  
    static void Main(string[] args)  
    {  
        Math m = new();  
        m = null;  
        GC.Collect();  
        // Console.ReadLine();  
    }  
    class Math  
    {  
        public Math()  
        {  
            System.Console.WriteLine("Ctor...");  
        }  
        ~Math()  
        {  
            System.Console.WriteLine("I'm Destructor...");  
        }  
    }  
  
}  

Answer 1

@Shervan360 , Welcome to Microsoft Q&A, based on my test, I reproduced your problem.

Here is some explanation.

First, I make sure that your console app is a .NET app based on the code Math m = new();.

Second, as the Microsoft doc finalizers said, there's no output when we used it in the NET app.

.NET 5 (including .NET Core) or a later version: There's no output, because this implementation of .NET doesn't call finalizers when the application terminates.  

Also, based on my test, it will not give output I'm Destructor... even if I used your code in a .NET Framework 4.8. console app.

After checking, I find that we need to use Trace.WriteLine instead of Console.WriteLine to show the output.

Tested result in .net framework 4.8 when using Trace.WriteLine:

Hope my explanation could help you.

Best Regards,
Jack

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