Most common or vicious mistakes in C# development for experienced C++ programmers

Question

What are the most common or vicious mistakes when experienced C++ programmers develop in C#?

Answer 1

1. Using structs in favour for classes all the time.
2. Using in, out and ref parameters all the time (This is a result of point 1).
3. Using int values as error conditions instead of using exceptions
4. Using the virtual keyword instead of override keyword.
5. Thinking that char is an 8 bit signed value.