Thursday, 19 April 2012

Some features of C#

This is a collection of some features of C# I found useful and interesting, given I am coming from a C++ background.

- it is easy to stringify enum values by using Enum.ToString Method
- it is possible to use strings in switch statement
- In C++, derived class constructor calls base class constructor by stating base class name:

...while in C# keyword base is used:

- C# does not allow multiple inheritance (class cannot inherit multiple base classes)

Abstract Classes

Both in C++ and C# abstract classes are designed to be base classes and can never be instantiated.
In C++, a class is abstract if has at least one pure virtual method.
In C#, a class is abstract if declared with abstract keyword. It may contain abstract methods and properties (they are declared as abstract and don't have implementation).
A non-abstract class derived from an abstract class must include actual implementations of all inherited abstract methods and accessors. Those implementations are method overrides and must be declared with override keyword.
Abstract methods are implicitly virtual.

Auto-Implemented Properties

Auto-implemented properties come very handy for properties with trivial accessors. Compiler creates a private, anonymous backing field that can only be accessed through the property's get and set accessors.

Don't try to implement auto-implemented properties. You'll end up having stack overflow! Example:

Object types and memory storage

In C++ there are POD (Plain Old Data) types (e.g. int, float, pointers, certain struct types,...see further explanations here) and non-POD types. Object of any type can be stored on the stack (e.g. if declared as a local variable) or on the heap (if created with new).

C# uses different type classification: there are value types and reference types. C# doesn't care where are they stored in memory. In C# a new can be used to store (value type) object either on the stack or on the heap.

Further reading:
Type Fundamentals
The Truth About Value Types
The Stack Is An Implementation Detail
C# Heap(ing) Vs Stack(ing) in .NET

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