Question

I am following MSDN guideline of implementing a Dispose Method. I’ve written my simple code to better understand and run the code step by step.

EDITED: changed title to better fit the problem

This is the code:

class Program {
    static void Main(string[] args) {
        Base0 base0 = new Base0();
        base0.Dispose();

        Console.WriteLine();
        Sub1 sub1 = new Sub1();
        sub1.Dispose();

        Console.ReadLine();
    }
}
class Base0 : IDisposable {
    private bool disposed;
    public Base0() {
        Console.WriteLine("Creating Base0!");
        this.disposed = false;
        // allocating some resources
    }
    public void Dispose() {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
    protected virtual void Dispose(bool disposing) {
        Console.WriteLine("Disposing " + this.GetType().ToString() + "!");
        if (!this.disposed) {
            if (disposing) {
                // disposing all managed resources
            }
            // disposing all unmanaged resources
        }
    }
    public void DoSomething() {
        if (this.disposed) {
            throw new ObjectDisposedException(this.GetType().ToString());
        }
    }
    ~Base0() {
        Dispose(false);
    }
}
class Sub1 : Base0 {
    private bool disposed;
    public Sub1() {
        Console.WriteLine("Creating Sub1!");
        this.disposed = false;
        // allocating some resources
    }
    protected override void Dispose(bool disposing) {
        Console.WriteLine("Disposing " + this.GetType().ToString() + "!");
        if (!this.disposed) {
            try {
                if (disposing) {
                    // disposing all managed resources
                }
                // disposing all unmanaged resources
            }
            finally {
                base.Dispose(disposing);
            }
        }
    }
}

This is the output:

Creating Base0!  
Disposing DisposeFinalizeMethods.Base0!  

Creating Base0!  
Creating Sub1!  
Disposing DisposeFinalizeMethods.Sub1!  
Disposing DisposeFinalizeMethods.Sub1!

I am confused because I expected that the last line would be saying “Diposing … Base0!”, the base type.

The code executes as it should, I’ve checked it ‘step by step’ many times, I understand it but there is something that I’ve missed. What am I missing?

Answer 1

OK, this is not about Dispose or IDisposable but about GetType.

this.GetType() is a call to a virtual method. When called in a base-class it will give the Type of the actual (derived) type.

To reproduce:

class A
{
    public virtual void Print()
    {
        Console.Write(this.GetType().Name);
    }
}

class B : A
{
    public override void Print()
    {
        base.Print();
        Console.Write(this.GetType().Name);
    }
}


        var b = new B();
        b.Print();

Will print BB.