I am studying the Dispose pattern in C#, and I understand that the Dispose method is used when there are unmanaged resources. For example, if I have an unmanaged resource in FirstClass, and FirstClass is contained within a Node class, I need to implement the Dispose method for both, right?

What I don’t understand the most is whether I need to call GC.SuppressFinalize(this); in every Dispose method.

GC.SuppressFinalize(this); instructs the garbage collector not to finalize, but does this mean that GC.SuppressFinalize(this); is only necessary in the Dispose method if the class has a finalizer? If that’s the case, I think it would be needed in both the Node class and BaseClass. However, since the Node class also has managed members, is it acceptable to suppress the finalizer in that case?

I am confused because there are nested classes with Dispose methods.

C# I rewrote it based on the advice.

  public class Node : IDisposable
  {
    public Node Next { get; set; } = null;
    public Node Child { get; set; } = null;
    
    public FirstClass FirstClassInstance { get; set; } = null;
    protected Boolean disposedValue = false;

    public Node()
    {
      FirstClassInstance = new FirstClass();
    }
    
    ~Node()
    {
      this.Dispose( false );
    }

    public void Dispose()
    {
      this.Dispose( true );
      GC.SuppressFinalize( this );
    }
    
    protected virtual void Dispose( Boolean disposing )
    {
      if( !disposedValue )
      {
        this.FirstClassInstance?.Dispose();
        this.FirstClassInstance = null;
        disposedValue = true;
      }
    }
  }
  
  public class FirstClass : BaseClass
  {
    private List<String> _nameList = [];
    
    public FirstClass()
    {
       _nameList.Add("A");
       _nameList.Add("B");
       _nameList.Add("C");
    }
    
    protected override void Dispose( Boolean disposing )
    {
      if( !disposedValue )
      {
        if( disposing )
        {
          // Managed resource release
          _nameList.Clear();
          _nameList = null;
        }
        
        base.Dispose( disposing ); // BaseClass Dispose
      }
    }
    
    protected override void CreateCppInstance()
    {
       CreateCppData( out _instance ); // C++ Function create
    }

    protected override void DeleteCppInstance()
    {
       DeleteCppData( ref _instance ); // C++ Function delete
    }
  }

  public class BaseClass :IDisposable
  {
    protected Boolean disposedValue = false;

    protected IntPtr _instance;  // ● Unmanaged Data

    public BaseClass()
    {
      CreateCppInstance();
    }    
    
    ~BaseClass()
    {
      Dispose( false );
    }
    
    protected virtual void CreateCppInstance()
    {
      throw new Exception();
    }

    protected virtual void DeleteCppInstance()
    {
      throw new Exception();
    }

    protected override void Dispose( Boolean disposing )
    {
      if( !disposedValue )
      {
        if( disposing )
        {
          // Managed resource release
        }
        // Unmanaged resource release
        DeleteCppInstance();
        disposedValue = true;
      }
    }

    public void Dispose()
    {
      this.Dispose( disposing: true );
      GC.SuppressFinalize( this );
    }
  }