Breaking changes in .NET 4.0

Question

There is a lot of information about new features and classes in new 4.0 however there are also changes that may affect existing applications, for example

1. Ti

Answer 1

Also note that SmtpClient now implements IDisposable so you should now use something like this:

using (var smtpclient = new SmtpClient())
{
  smtpclient.Send(message);
} 

According to this page there might be more of these 'hidden jams' inside the .NET 4.0 framework. And the author suggest to find them by using FxCop on your code.