.ForEach wIth No GC.cs

using System;
using System.Collections.Generic;

public class C {
    List<int> CoppyToList = new List<int>();
    List<int> FooList = new List<int>();
    
    // foreach by enumerator
    public void ForeachByEnumerator() 
    {
        foreach(var key in FooList)
        {
            CoppyToList.Add(key);
        }
    }
    
    // .ForEach ( GC )
    public void ForEachWithActionGC() 
    {
        FooList.ForEach(_key=> CoppyToList.Add(_key));
    }
    
    
    // .ForEach ( None GC )
    Action<int> action;     
    public void ForEachWithActionNonGC()
    {
        FooList.ForEach(action ?? (action = (key)=>{CoppyToList.Add(key);}));
    }
}

​.ForEach wIth No GC.decompiled.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Security;
using System.Security.Permissions;

[assembly: CompilationRelaxations(8)]
[assembly: RuntimeCompatibility(WrapNonExceptionThrows = true)]
[assembly: Debuggable(DebuggableAttribute.DebuggingModes.Default | DebuggableAttribute.DebuggingModes.DisableOptimizations | DebuggableAttribute.DebuggingModes.IgnoreSymbolStoreSequencePoints | DebuggableAttribute.DebuggingModes.EnableEditAndContinue)]
[assembly: SecurityPermission(SecurityAction.RequestMinimum, SkipVerification = true)]
[assembly: AssemblyVersion("0.0.0.0")]
[module: UnverifiableCode]
public class C
{
    private List<int> CoppyToList = new List<int>();

    private List<int> FooList = new List<int>();

    private Action<int> action;

    public void ForeachByEnumerator()
    {
        List<int>.Enumerator enumerator = FooList.GetEnumerator();
        try
        {
            while (enumerator.MoveNext())
            {
                int current = enumerator.Current;
                CoppyToList.Add(current);
            }
        }
        finally
        {
            ((IDisposable)enumerator).Dispose();
        }
    }

    public void ForEachWithActionGC()
    {
        FooList.ForEach(new Action<int>(<ForEachWithActionGC>b__3_0));
    }

    public void ForEachWithActionNonGC()
    {
        FooList.ForEach(action ?? (action = new Action<int>(<ForEachWithActionNonGC>b__5_0)));
    }

    [CompilerGenerated]
    private void <ForEachWithActionGC>b__3_0(int _key)
    {
        CoppyToList.Add(_key);
    }

    [CompilerGenerated]
    private void <ForEachWithActionNonGC>b__5_0(int key)
    {
        CoppyToList.Add(key);
    }
}

​​.sharplab.json

{
    "version": 1,
    "target": "C#",
    "mode": "Debug"
}