C#

if ((MyObject is INotifyCollectionChanged)&& (MyObject is INotifyPropertyChanged))
        Console.WriteLine("This object implements both INotifyPropertyChanged and INotifyCollectionChanged");

if (!(MyObject is INotifyCollectionChanged) && (MyObject is INotifyPropertyChanged))
    Console.WriteLine("This object implements only INotifyPropertyChanged");

public static IObservable<EventPattern<PropertyChangedEventArgs>> Observes<TSource>(this TSource MyObject) where TSource : INotifyPropertyChanged
{
    return null;
}

public static IObservable<EventPattern<NotifyCollectionChangedEventArgs>> Observes<TSource>(this TSource MyObject) where TSource : INotifyCollectionChanged
{
    return null;
}

public static IObservable<T> Observes<TSource>(this TSource MyObject) where TSource : object, T: object
{
    if ((MyObject is INotifyCollectionChanged)&& (MyObject is INotifyPropertyChanged))
        Console.WriteLine("This object implements both INotifyPropertyChanged and INotifyCollectionChanged");
 
if (!(MyObject is INotifyCollectionChanged) && (MyObject is INotifyPropertyChanged))
    Console.WriteLine("This object implements only INotifyPropertyChanged");
}

public static IObservable<T> Observes<TSource, T>(this TSource MyObject) where TSource : object, T: object

Sascha Lefèvre wrote:

But: Lifting the type constraint for TSource from IPropertyChanged / INotifyCollectionChanged to Object for the sake of having one method is rather "dirty"

Kenneth Haugland wrote:

I could write where T : INotifyPropertyChange,INotifyCollectionChanged but not a clause that said that it cound not implement some interface.

Dave Kreskowiak wrote:

Also, what if the use accidentally click SaveAs? How are you giving them a way out without performing the Save operation?

private void saveFileDialog1_FileOk(object sender, CancelEventArgs e)
{
    if (saveFileDialog1.FileName == @"C:\Users\SomeUser\Desktop\NoGo.xxx"
        || saveFileDialog1.FileName.ToLower().Contains("forbidden"))
    {
        e.Cancel = true;
    }
}

float result;

if (float.TryParse(tbUserName.Text, NumberStyles.Number, System.Globalization.NumberFormatInfo.InvariantInfo, out result))
{
    // 'result has valid value
}
else
{
    // no float there: handle error ?
}

int price;
if (!int.TryParse(Texbox1.Text, out price))
   {
   ... Report problem to user and ask him to re-enter
   return;
   }
s.Price = price;
s.Save();