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.

Answer 2

• the difference between struct and class in the two
• the difference between a using alias and a typedef
• when do my objects get collected? how do I destroy them now?
• how big is an int? (it is actually defined in C#)
• where's my linker? (actually, Mono does have a full AOT linker for some scenarios)

Answer 3

using Hungarian Notation and other C++ naming conventions

private int m_iMyIntField;
class CWidget { ... }

Answer 4

• RAII vs IDispose
• value type vs ref type (struct vs class, boxing and unboxing, etc.)

Answer 5

Thinking that "garbage collection" = "I never have to worry about object lifetime at all". For instance, opening a FileStream and forgetting to close it.

Or:

1. Allocating a lot of objects
2. Putting them in a big global dictionary (usually after "I know, I'll make a cache")
3. Wondering why the application's memory usage always goes up and never down ("but it's supposed to garbage collect!")

Answer 6

Confusing "pass by reference" and "reference type":

void GetAnArray(int input, ref string[] output);

(Compare with C++: void getAnArray(int input, std::vector<std::string>& output);)