baigiang chuyendephattrienphanmem linq remoting 23-10-2010

7/30/2019 BaiGiang ChuyenDePhatTrienPhanMem LINQ Remoting 23-10-2010

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Week 4: LINQ

Basic concepts

LINQ requirements

Concepts

Types LINQ to objects

LINQ to SQL

LINQ to Entity LINQ to XML


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2. New features in langauge

Generics

Implicitly Typed Variables

Object Initializers

Anonymous Types

Extension Methods

Lambda Expressions


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2.0 Generics

the creation of various types ofcollection

type safety

Binary Code Reuse

using System.Collections.Generic;


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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


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2.1 Implicitly Typed Variables

Example

var x = new OledbConnection();


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2.1 Implicitly Typed Variables

Note

Alwayls declare the type if we know

Implicitly Typed Variables are suited for LINQ and

anonymous type


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2.2 Object Initializers

Constructor

Allow to assign values to object properties(fields) when create object

We do not have to explicitly invoke aconstructor

Usefull in any context

Especially userfull in LINQ expressions


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2.2 Object Initializers

Example


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2.3 Anonymous Types Implicitly type functionality for objects

Set property values to object without writingclass definition

The resulting class has no usable name

Class name is generated by compiler, inheritsfrom Object

The result: an anonymous type that is notavailable at source code level

Also called Projections


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2.3 Anonymous Types When to user anonymous types

Need a temporary object to hold related data

Dont 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


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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


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2.4 Extension Methods Special kind of Static method

Allow the addition of methods to an existingclass

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


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2.4 Extension Methods Example


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2.4 Extension Methods Example


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2.4.a Delegate Delegate

refers to method.

When initialize a delegate, we initialize it with

method.


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2.4.a delegate: example


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2.4.a delegate: why


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2.4.a delegate: why


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2.4.a delegate: with anonymous


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2.4.a delegate: with anonymous:

return to example


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2.5 Lambda Expressions Lambda Expressions is an Anonymous function

A funciton without a name Perform action , return a single value

Can be used wherever a delegate type is valid

Why? Allow a functions caller to define the action

Not just pass parameters

Lambda expressions provide a clearer syntax foranonymous delegates


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2.5 Lambda Expressions: delegate Syntax

parameters => expression a functional superset of anonymous methods

Lambda expressions can "infer" parameter types,

even if you omit them

Lambda expressions can use both statement

blocks and expressions


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2.5 Lambda Expressions in C# Use lambda operator =>

Read as goes to x=>x+3 if x=1 then 4 is returned

X=> x==5: if x=5, True is returned

(x,y)=> x+y if x=2, y=4 then 6 is returned

(x,y)=>x==y if x=2, y=4 then False is returned


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2.4.a lambda example


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2.4.a delegate: turn back to

example: lambda


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3. LINQ Language Integrated Query

LINQ does create a new way of looking at enumerations of

data, and gives out-of-the-box functionality for them

L2O

L2S

L2E

L2X

L2D


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3. LINQ example 1


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3. LINQ requirements .Net framework 3.5

VS 2008

Work with VS 2005: not recommended

C#

VB.NET


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3. What is LINQ a programming model that introduces

queries as a first-class concept SQL-like syntax used in LINQ is called a query

expression

provides a set of standard query operators

common tasks: query, ordered, grouped oraggregated from

an existing in-memory collection, a database, an XML file or

many other sources


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1. What is LINQ How LINQ works?

compiler generates code More detail: later


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1. What is LINQ: Language Integration

Language in query expression


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1. What is LINQ: LINQ Flavors covers many data domains

these implementations is defined through a set ofextension methods

The access to these features is controlled by the

imported namespaces can be extended to support other data domains


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3. What is LINQ: Everywhere LINQ to Objects, LINQ to SQL, and LINQ to

XML LINQ is an extendable technology

open-source product: LINQExtender

build your own LINQ extensions

Other providers


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3. What is LINQ: Everywhere


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3. LINQ new features of.NET framework support for

LINQ: Extension methods, lambda expressions

are used extensively to build queries.

anonymous types : to allow data to be returnedfrom a query without the need to first define

a class or structure,

generics : creation of various types ofcollection


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3. LINQ basic 2 types of Syntax

Query syntax Method syntax


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4. LINQ syntax example ??????????

??????????


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3. LINQ basic: Query syntax vs

Method syntax

have to "redeclare" person each time in the lambda expressions

Query syntax => Method syntax

certain queries can only be expressed in method syntax and some of

those require lambda expressions.

Performance???

query syntax is a lot more readable than method syntax

Tips

Use the Query Expression syntax wherever possible, its easier to read;

If you need to mix the Extension Methods with Query Expressions, put them at the

end;

Keep each part of the Query Expression on separate lines


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3. Exer Convert CVS (comma separated values )

string to int array S =20;10;2;0;1;0

=> array of int {20,10,2,0,1,0}


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5. LINQ Execution deferred execution, or lazy loading

Queries that return a single value or object doexecute immediately. However, those that return

a list of items are usually not executed until the

first time that the results are used.

Lazy means "don't do the work until you absolutely have to."

Deferred means "don't compute the result until the caller

actually uses it."


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5. LINQ Execution Example deferred execution

If you want a query to

be realized

immediately,

call ToList, ToArray orany of the other

operators that need to

enumerate the entire

sequence to return a

result.


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7. LINQ to SQL Topics

Concepts Mapping object

Datacontext

Actions Query

Insert, update, delete

Join

Stored procedure


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7. LINQ to SQL: concepts Created to bridge the differences between

relational data and CLR object Mapping Classes to Tables

Using code or Graphical Designer for Mapping

Creating Entity Classes

Tableclass, Rowobject


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7. LINQ to SQL Using the Graphical Designer for Mapping

Server connection

Adding a designer file (dbml): LINQ to SQL

Classes

Drag drop from Server Explorer ->design surface


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7. LINQ to SQL: concepts The DataContext

retrieve objects from database

Track changes

Update from object to database


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7. LINQ to SQL: concepts Translating LINQ to SQL


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7. LINQ to SQL: actions Select data


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7. LINQ to SQL : actions Modifying and Saving Entities


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7. LINQ to SQL : actions: insert


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7. LINQ to SQL : actions: delete


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7. LINQ to SQL : actions: update


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7. LINQ to SQL: actions: join


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7. LINQ to SQL : actions Using stored procedure

In the Server Explorer-> select stored node->drag drop on design interface


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7. LINQ to SQL : actions Join tables


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7. LINQ to SQL : actions Relationships

Querying Across Relationships


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6.1 LINQ exercise Change database to MS SQL Server

Using L2S Display data in Listview

Insert new contact record

Update contact record Delete selected records in list

Button Search contact

L2S L2O


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LINQ to Object Restriction Operators

Projection Operators

Partitioning Operators

Ordering Operators Grouping Operators

Set Operators

Conversion Operators

Element Operators

Generation Operators Quantifiers

Aggregate Operators

Miscellaneous Operators

Custom Sequence Operators

Query Execution Join Operators


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6.1 Example: select controls


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Week 7: NET REMOTING Modern applications are no longer stand-alone

applications

What Is .NET Remoting?

provides a solution for communication between

application domains

ASP.NET Web services (WS) vs


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ASP.NET Web services (WS) vs

.NET Remoting (NR) 1. WS: only be accessed over HTTP; NR various

protocols like TCP, HTTP etc.

2.WS stateless environment, NR state management 3. ES more reliable than .NET Remoting.

4. WS are easy to create and use, NR are complex tobe created.

5. WS across platforms, NR requires client to be builtusing .NET

6. WS support datatypes defined in the XSD type

system while .NET remoting provides support for richtype system using binary communication.


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.Net Remoting components A remotable object.

A host application. listen to requests for the hosted remotable

object.

A client application. requests for the remotable object.


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How Does .NET Remoting Works? In the client

create a new remotable object =>creates a proxyobject

When client call method => call method on

proxy=> server=> return to proxy => client


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Remoting makes an object in server available

to code in client => marshalling 2 ways to marshal an object

Marshal by value

the server creates a copy of the object passes thecopy to the client

Marshal by reference

the client creates a proxy for the object and then usesthe proxy to access the object


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Marshaling marshaling by value vs marshaling by

referenceexecutable functionalitydirectly within its own

process

must implement the

ISerializable interface


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Marshal by reference: multi

Marshal by reference object. Clients in other app domains interact with marshal by

reference objects using a proxy. Clients in the same app domain as the object have a

direct reference on the object.


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Marshal by reference 2 typed

Server-Activated Objetcs (SAO)

Client-Activated Objects (CAO) Server-Activated

lifetime is controlled by server

Use when there are clients sharing the same server object

Its a one-to-many relationship between the server object and clients

Singleton SingleCall

Client-Activated Objects lifetime is controlled by the client

Use when multiple server instances of the same kind need to be run onthe server at the same time

one-to-one relationship between each server object and itscorresponding client


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Client-activated objects

Client-activated objects. Each client gets an independent object for its use. Like the

classic client-server model, clients can still share objects.


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Client-activated objects: singlecall

In the single-call activation model, .NET creates an object for each call, and disposes

of it between calls.


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Client-activated objects: singleton

With a server-activated singleton object, all clients share the same well-known

object.


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Channel the medium through the which the messages

would be transferred The remote objects are to communicate with

one another and channels do this transport

job of communication. The two existing channels

HttpChannel and TCPChannel

Implementing .NET Remoting


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Creating remote object

Create host Listen

Channel

Type of activated object

uri

A client application domain

Getobject from server


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A. Creating a Remote Object Creating a Remote Object

declare a remotable class inherit the MarshalByRefObject

build the project, generate DLL file.

public class Class1:MarshalByRefObject

{

public string layten( )

{

return server + Now.date.toString();}

}


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B. Build host server

TcpServerChannel chnl = new TcpServerChannel(3999);

ChannelServices.RegisterChannel(chnl,false);

RemotingConfiguration.RegisterWellKnownServiceType(typeof(

Class1), "class1.soap", WellKnownObjectMode.SingleCall);

registers our created class and a channel for remoting


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C. Client application

TcpChannel chnl = new TcpChannel();

ChannelServices.RegisterChannel(chnl,false);

Class1 obj = (Class1)Activator.GetObject(typeof(Class1),

"tcp://192.168.210.34:3999/class1.soap");

this.Text = obj.layten();


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6.1 Remoting exercise Change to Remoting App

Host server Contact remoting object

Client display contact in Listview

baigiang chuyendephattrienphanmem linq remoting 23-10-2010

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