This document provides an overview of advanced C# concepts, including: - C# can be used to create various types of applications like console apps, Windows forms, web services, and ASP.NET MVC apps. - Assemblies are deployment units that contain code and metadata. They can be EXEs or DLLs. - Types in C# can contain fields, methods, properties, and events. Methods are not virtual by default. Access modifiers include private, protected, internal, and public. - Objects are allocated in memory and cleaned up through constructors, finalizers, and the garbage collector. Exceptions provide a way to handle errors.

1. C# Advanced
Part 2

2. Applications
• Console Windows apps
• Windows Forms
• Web services, WCF services
• Web forms
• ASP.NET MVC apps
• Windows services
• Libraries

3. Assembly
• Is a deployment unit
• .EXE or .DLL
• Contains manifest + code
(metadata tables + IL)

4. Types
Can contain:
• Constant
• Field
• Instance constructor
• Type constructor
• Method. Method is not virtual by default.
Virtual, new , override, sealed, abstract

5. Types (cont’d)
• Property. Can be virtual
• Overloaded operator
• Conversion operator
• Event. Can be virtual
• Type

6. Access modifiers
• Private
• Protected (Family)
• Internal
• Family and assembly -- Not supported in C#
• Family or assembly (protected internal)
• Public

7. Types
• Value types – stack, inline
• Reference types – heap, by reference

8. Object lifetime
• Allocate memory. Fill it with 0x00.
• Init memory -- constructor.
• Use the object -- call methods, access fields.
• Cleanup.
• Deallocate memory (only GC is responsible for
this).

9. Object References
• CLR knows about all references to objects.
• Root reference (in active local var or in static
field).
• Non-root reference (in instance field)

10. Finalization
• Mechanism that allows the object to correctly
cleanup itself before GC releases memory.
• Time when finalizers are called is
undetermined.
• Order in which finalizers are called is
undetermined.
• Partially constructed objects are also finalized

11. IDisposable
• Used when the object needs explicit cleanup

12. What are Exceptions?
• An exception is any error condition or
unexpected behavior encountered by an
executing program.
• In the .NET Framework, an exception is an object
that inherits from the Exception Class class.
• The exception is passed up the stack until the
application handles it or the program terminates.

13. Use Exceptions or not use exceptions?
-
• Вони невидимі з викликаючого коду.
• Створюються непередбачувані точки виходу з метода.
• Exceptions повільні. (exceptions use resources only when an exception occurs.)
+
• Зручність використання.
• Інформативність отриманих помилок більша по відношенні до
статус-кодів.
• Принцип використання. Throw на самий верхній рівень.
• Більш елегантні архітектурні рішення та зменшення часу
розробки.

14. C# Exception handling
• try…catch…finally
• throw
• Catch as high as you can
• try{ }
catch(Exception1){ /*exception1 handler*/ }
catch(Exception2) { /*exception2 handler*/ }
catch(Exception) { /*exception handler*/ }

15. IDisposable
• The primary use of this interface is to release
unmanaged resources.
• When calling a class that implements the
IDisposable interface, use the try/finally
pattern to make sure that unmanaged
resources are disposed of even if an exception
interrupts your application.

16. Working with streams
var fileStream = new FileStream(@"PathTofile", FileMode.Open, FileAccess.Read);
try
{
//Note: read from file stream here
}
finally
{
fileStream.Dispose();
}
//Note: you can use file stream here, but this is bad idea
using (var fileStream = new FileStream(@"PathTofile", FileMode.Open, FileAccess.Read))
{
//Note: read from file stream here
}
//Note: fileStream is not accessible here

17. Attributes
• Attributes provide a powerful method of
associating declarative information with C#
code (types, methods, properties, and so
forth).

18. Aspect Oriented Programming
• Logging
• Data validating
• Security mechanism
• …

19. Validation sample (AOP sample)
public class User
{
[StringLengthValidator(1, 255, MessageTemplate = "Login cannot be empty.")]
public string Login { get; set; }
[StringLengthValidator(1, 127, MessageTemplate = "Domain cannot be empty.")]
public string Domain { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
[StringLengthValidator(1, 50, MessageTemplate = "Email cannot be empty.")]
public string Email { get; set; }
}
http://msdn.microsoft.com/en-us/library/ff648831.aspx - Enterprise Library Validation Application Block

20. Custom attributes
- Creating
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
public class LoggingRequiredAttribute : Attribute
{
}
- Usages
public class UserService
{
[LoggingRequired]
public static void CreateUser()
{
//Note: logic here
}
public static void EditUser()
{
//Note: logic here
}
}

21. Questions?