What are the examples of design patterns within the C# language [on hold]

I would like to gather examples of design patterns used by default in C# language. I want them to be language-level and C# / .Net only

For example:
foreach loop and IEnumerable - Iterator Pattern
events - Observer
"I/O streams in Java are the example of decorator".

This is really interesting and helps easily understand the structure and purpose of the patterns, but I am unable to google the right phrase for gathering a broad mass of such examples!