Refresher/csharp
(Redirected from Refresher/m/csharp/Database)
This is a refresher course for those who need to review basic knowledge of C# (csharp).
Basic Concepts
edit- Comment styles: Single-line (//), multi-line (/* */) and XML documentation comments (///)
- delegate (function pointers in C++): an object encapsulates reference to a method
- HashTable: datatype allowing data retrieval by unique key
- Interface: an approach to multiple inheritance, contains only abstract members (events, methods, properties) and no constants, data fields, constructors, and destructors
- multicast delegate: a delegate that points to and eventually fires off several methods
- Three-tier: presentation (UI), business (logic and underlying code) and data (from storage or other sources) layers
Basic Classes
edit- Debug vsTrace class: debug builds only or both debug and release builds
- Localization namespaces: System.Globalization and System.Resources
- System.Array.CopyTo() vs System.Array.Clone(): deep vs shallow copy of an array
- System.Text.StringBuilder over System.String: more efficient when a lot of manipulation is done to the text
Basic Limitation
edit- System.Array: cannot store multiple data type
Basic Operations
edit- ACID rule of thumb for transactions: Transaction must be Atomic (independent off other transactions), Consistent (committed or roll back), Isolated (other transactions cannot see intermediate results), Durable (values persist if committed)
- ASP.NET Web application debugging: attach the aspnet_wp.exe process to the DbgClr debugger
- Assembly deployment: MSI installer, CAB archive, and XCOPY command
- Descending sorting: by calling Sort() and then Reverse() methods
- Immediate window in VS.IDE: change value of a variable while debugging a C# application
- Test cases in unit testing: Positive, negative and exception
- try { control transfer only after finally block executed } catch (Exception ex) { } finally { executed if no exceptions but exceptions herein are not handled }
Authentication
edit- SQL Server authentication: untrusted as username and password are not checked with the Active Directory
- Windows Authentication: trusted as username and password are checked with the Active Directory
Database
edit- Initial Catalog: name of wanted database in a Connection String
Accessibility Modifiers
edit- Class inheritance: colon + base class
- Private class-level variables: inherited but not accessible
- Value: keyword for implicit input name of the set method in object classes
- Protected class-level variables: available to classes in the same namespace
- Protected internal: available to derived classes, and classes within the same Assembly, and the base class
- Default constructor: disappears when any constructor is written
- System.Object: top .NET class that everything is derived from
- Method overriding: changing the method behavior for a derived class
- Virtual method: can be over-ridden but cannot change method signature
- Sealed class (in Java, final class): cannot be inherited
- Sealed method: method cannot be inherited but class can when not sealed
- Abstract class methods: not all must be abstract, some can be concrete
- Abstract class required when at least one of the methods in the class is abstract
- Abstract method: require non-abstract derived classes to provide their own implementation of this method
- Interface class? an abstract class with public abstract methods all of which must be implemented in the inherited classes
- Interface class methods: all must be abstract and public and thus accessibility modifiers not needed
- Multiple interfaces: can be inherited
- Namespace class: classes are declared inside a namespace
Delegates How and When
edit- Delegate: a class -- usable if declared and instantiated
- Delegate use: passed around as a parameter, and invoked by the receiving object
- Delegate example 1: success = MyAddressProvider.HandleCampaign(WhatToDoWithAddresses)
- Delegate example 2: MyMenuItem.Click += new System.Windows.RoutedEventHandlerMyMenuItem_Click)
Singleton
edit- Singleton design pattern: interface allowing a class to enforce single instantiation
- C# singleton example: http://www.dotnetperls.com/singleton