06.1 .Net memory management


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06.1 .Net memory management

  1. 1. C# Advanced Part 2
  2. 2. Applications• Console Windows apps• Windows Forms• Web services, WCF services• Web forms• ASP.NET MVC apps• Windows services• Libraries
  3. 3. Assembly• Is a deployment unit• .EXE or .DLL• Contains manifest + code (metadata tables + IL)
  4. 4. TypesCan contain:• Constant• Field• Instance constructor• Type constructor• Method. Method is not virtual by default. Virtual, new , override, sealed, abstract
  5. 5. Types (cont’d)• Property. Can be virtual• Overloaded operator• Conversion operator• Event. Can be virtual• Type
  6. 6. Access modifiers• Private• Protected (Family)• Internal• Family and assembly -- Not supported in C#• Family or assembly (protected internal)• Public
  7. 7. Types• Value types – stack, inline• Reference types – heap, by reference
  8. 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. 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. 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. 11. IDisposable• Used when the object needs explicit cleanup
  12. 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. 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. 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. 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. 16. Working with streamsvar 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 ideausing (var fileStream = new FileStream(@"PathTofile", FileMode.Open, FileAccess.Read)){ //Note: read from file stream here} //Note: fileStream is not accessible here
  17. 17. Attributes• Attributes provide a powerful method of associating declarative information with C# code (types, methods, properties, and so forth).
  18. 18. Aspect Oriented Programming• Logging• Data validating• Security mechanism• …
  19. 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. 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. 21. Questions?