Chuyên đề phát triển phần mềm LINQ remoting

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Nội dung Text: Chuyên đề phát triển phần mềm LINQ remoting

Week 4: LINQ • Basic concepts – LINQ requirements – Concepts • Types – LINQ to objects – LINQ to SQL – LINQ to Entity – LINQ to XML
2. New features in langauge • Generics • Implicitly Typed Variables • Object Initializers • Anonymous Types • Extension Methods • Lambda Expressions
2.0 Generics • the creation of various types of collection • type safety • Binary Code Reuse – using System.Collections.Generic;
2.1 Implicitly Typed Variables • Implicitly Typed Variables – Declare variables without specifying their type – Strongly type, not variant, not object – VS will determinr type • Predict what the compiler will choose • Intellisense support – Type inference -> most general • “3/10/2010” -> string, not date
2.1 Implicitly Typed Variables • Example var x = new OledbConnection();
2.1 Implicitly Typed Variables • Note – Alwayls declare the type if we know – Implicitly Typed Variables are suited for LINQ and anonymous type
2.2 Object Initializers • Constructor • Allow to assign values to object properties (fields) when create object • We do not have to explicitly invoke a constructor • Usefull in any context – Especially userfull in LINQ expressions
2.2 Object Initializers • Example
2.3 Anonymous Types • Implicitly type functionality for objects – Set property values to object without writing class definition – The resulting class has no usable name – Class name is generated by compiler, inherits from Object – The result: an anonymous type that is not available at source code level • Also called Projections
2.3 Anonymous Types • When to user anonymous types – Need a temporary object to hold related data – Don’t need method – If we need a different set of properties for each declaration – If we need to change the order of properties for each declaration
2.3 Anonymous Types • When not to user anonymous types – Need to define methods – Need to define another variable – Need to shared data across methods
2.4 Extension Methods • Special kind of Static method • Allow the addition of methods to an existing class – Without creating a new derived type – Without re-compiling or modifying the original type • Called The Same way regular methods are called • Define in static class
2.4 Extension Methods • Example
2.4 Extension Methods • Example
2.4.a Delegate • Delegate – refers to method. – When initialize a delegate, we initialize it with method.
2.4.a delegate: example
2.4.a delegate: why
2.4.a delegate: why
2.4.a delegate: with anonymous
2.4.a delegate: with anonymous: return to example