McGraw-Hill © 2010 The McGraw-Hill Companies, Inc. All rights reserved.

Chapter 6

Services

McGraw-Hill 6-2

Objectives

• Discuss the concepts of Windows Communication Foundation (WCF) Services and understand the terminology

• Create a WCF Service

• Add a service reference to a Windows project

• Consume a WCF Service from a Windows project

• Perform calculations in a WCF Service

• Access data through a WCF Service

• Consume a third-party WCF Service

McGraw-Hill 6-3

Concepts and Terminology - 1

• Communication starts with a client application

• The service application waits for a client to send

a message and then responds

– A single application can be both a client and a service

• WCF uses Web Service specifications

– WS-Security and WS-ReliableMessaging for example

• WCF can communicate with other platforms that

support SOAP protocol

– Also can work with simple XML formats such as RSS

McGraw-Hill 6-4

Concepts and Terminology - 2

• An endpoint indicates where messages

can be sent (address), how sent (binding),

and a contract defining the service

provided

– Referred to as the “abc” of the service

• Address, binding, contract

– Endpoints are handled by VB when a service

is used by adding a service reference in the

client application

McGraw-Hill 6-5

Concepts and Terminology - 3

• The Web.config file indicates the appropriate address and binding – The address is localhost when using the Visual Studio web

server

• WCF Service has two files by default – IService.vb and Service.vb

McGraw-Hill 6-6

Concepts and Terminology - 4

• An operation contract shows a function or

sub procedure header listing parameters

and return type

– Each operation contract requires the method

to be written in the Service.vb file

• After a service is created, it may be used

or consumed from another application

McGraw-Hill 6-7

Windows Communication

Foundation (WCF)

• A WCF Service component may include

XML, SOAP, WSDL, and HTTP services

– VS handles most of the details

• Each of the technologies can be thought of

as protocols, or “rules” that both sides

understand

– Used to store, locate, and use WCF Services

McGraw-Hill 6-8

XML

• A standard method for storing data that

can be transferred easily from one

machine or platform to another

• Key advantage for Web services is that

data are transmitted in a text format rather

than in binary

– Allows data to pass through many firewalls

– .NET Framework takes care of the details

McGraw-Hill 6-9

SOAP

• Simple Object Access Protocol (SOAP) is the

popular protocol for sending data

• Includes a set of rules for handling requests and

responses

– Includes class names, method names, and

parameters

• SOAP works with XML but does not include a

specific protocol for transporting the response

and request packets

– The transport protocol is most frequently HTTP

McGraw-Hill 6-10

WSDL

• Web Services Description Language

(WSDL)

– Contains information about the names of

methods, the parameters that can be passed,

and the values that are returned from the

functions

McGraw-Hill 6-11

More Acronyms

• Uniform resource identifier (URI) uniquely

identifies a resource on the Web

– More generic than URL

• For technical specifications, industry standard term

URI is preferred to URL

– Always end URI or URL with a slash to avoid

an extra trip to the server

McGraw-Hill 6-12

Creating a WCF Service

• Create a solution and the consumer

application

• Add a WCF Service

• Rename the WCF Service

• Create the operation contract

• Code the WCF Service

• Test the Service

McGraw-Hill 6-13

Consuming a WCF Service

• Create a project with a Service reference

• Add a Service reference

• Write the code

• Run the completed application

– If there is an error while running the service,

change to debug = true in the Web.config file

for the service

McGraw-Hill 6-14

Performing Calculations

in a WCF Service

• Add the contract to the Service

– Add the method found on page 260 to the class

• Create a client or consumer application

• Add a service reference to the project and controls to the form

McGraw-Hill 6-15

Accessing Data

through a WCF Service

• Easily create a service that returns a

dataset

– Similar to the data tier in a multitier data

project

• The component fills a DataSet

– Returns the DataSet to the calling program

from a WCF Service function

McGraw-Hill 6-16

Creating a Data WCF Service - 1

• Divides the

data tier into

two separate

projects

– The data

access tier

and the

data entity

tier

McGraw-Hill 6-17

Creating a Data WCF Service - 2

• Create the solution

• Create the WCF Service

• Add the data-tier components

• Add the data source

• Configure the DataSource

• Code the WCF Service

• Set up the client user interface

• Write the client code

McGraw-Hill 6-18

The DataSet Merge Method

• Merge method of the DataSet class is

used to merge rows, tables, or datasets

that have similar schemas

• Create a service that defines a dataset

– Call the Fill or Get method from the table

adapter

• Merges the resulting data set into the data set

defined by the service

PubsDataSet.Merge(ADataService.GetAuthors)

McGraw-Hill 6-19

Placing Validation and Access

Code in the Data-Tier Projects

• Click any empty spot of the DataSet Designer to

view the dataset’s properties

– The DataSet Project property determines where the

Dataset.Designer.vb code file resides

• To write code for a data access tier, add a class

library item to the project

• Write Fill and Update methods for data access in

the Data Manager file of the data access tier

McGraw-Hill 6-20

Writing Validation Code

• In a service place the validation code for

updates in the DataEntity tier

– Double-click on the table in the DataSet

Designer

– The class is added to the DataEntity project

– Write dataset validation procedures in the file

McGraw-Hill 6-21

Setting Properties of

the Dataset Fields

• Double-click on the Dataset.xsd file in the

Solution Explorer

– Select each field name

• View or set its properties

– Set Caption, DefaultValue and other

properties

McGraw-Hill 6-22

Working with Related Tables

• Hands-on project uses related tables

– Similar to creating a single-table application

• Form must contain two dataset Merge

methods

– Specify the table and dataset names

• Add a query for each table to return in the

DataSet Designer window