C#

Bitmap bitmap = new Bitmap(200, 200);
IntPtr hBitmap1 = bitmap.GetHbitmap(); // No exception because bitmap hasn't been disposed.

bitmap.Dispose();

try
{
	IntPtr hBitmap2 = bitmap.GetHbitmap();
}
catch (ArgumentException ex)
{
	Console.WriteLine("Bitmap has been disposed!");
}

OriginalGriff wrote:

Until I finally twigged: You can't derive from a Bitmap anyway: it's a sealed class...

Richard Deeming wrote:

The only problem is, you can't write a class derived from Bitmap, as it's sealed.

public static class Extensions
{
    public static List<Foo> GetModified(this List<Foo> list)
    {
        if ((list == null) || (list.Count == 0)) return null;

        return list.Where(r => r.GetThisFooDirty()).ToList();
    }
}

public class Foo
{
    public string Name { private set; get; }

    private bool ThisFooIsDirty { set; get; }

    public bool GetThisFooDirty() { return ThisFooIsDirty; }

    public void SetThisFooDirty(bool dirtyness) { ThisFooIsDirty = dirtyness; }

    public Foo(string fooName)
    {
        Name = fooName;
        ThisFooIsDirty = false;
    }
}

List<Foo> fooList = new List<Foo>
{
    new Foo("foo1"),
    new Foo("Foo2"),
    new Foo("Foo3")
};

fooList[1].SetThisFooDirty(true);
fooList[2].SetThisFooDirty(true);

var whoIsDirty = fooList.GetModified();