unit 27 - web server scriptingwiki.hct.ac.uk/_media/computing/btec/level3/2011_2... · unit 27 -...

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Unit 27 - Web Server Scripting

Lesson 5 - Data Access with ASP.NET

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Last Week

• Capturing User Information

• Processing User Input

• Validation

• Server Side Processing

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This week

• Data display

• Storing Data

• Accessing Database data

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Multiline display

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Using Arrays to store data

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An array is created and

loaded with data (colours) at

page load time into a list

box control. It will only be

loaded the first time the

page is displayed –

ispostback property!

When the button is clicked

the text is concatenated

with the colour selected and

the forecolor property of the

label control is changed to

the selected colour.

When the program is run, a

colour is selected from the

drop down lost box and the

button is clicked. The text is

then displayed in the correct

colour in the text box.

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When the

user selects

a colour –

the text is

displayed

using the

colour

selected.

ArrayLists

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Using ArrayLists which are a

special kind or array that can store

a collection of elements and add or

remove elements easily. They do

have performance considerations

as are they require more

processing power. So if it just a

simple list of elements then use an

ordinary array.

In this example- additional controls

have been added to the form so

that the user can select the font for

display as well as the colour.

The font names are added to the

fontlist on page load and the

datasource (fontlist) is identified as

the source of data and bound to

the dropdownlistbox.

Notice that the databinding is done

in one statement – you do not have

to iterate through the whole

collection to add it to the list. You

can do this ordinary arrays as

well!!

The messages output are changed

to reflect the font.

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Adding Array items

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Hash Tables

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Hashtables

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Hash tables are used to associate keys with values that can identify them.

An array has an index number which we can refer to but you would need to

know the index number to find the list entry you wanted. A hash table

replaces the index number system with a key that is specified for each list

item which relates to a corresponding value.

A good use of hash tables is with country codes where the abbreviations

would be UK for example and then when selected the whole country name

would be displayed.

Have amended the example to allow the user to select a value from a list

and then to display the associated text item.

Notice that the databind this time is for the hashtable keys!!

There is a sortedlist collection that works in exactly the same way as the

hashtable but the keys are automatically sorted into alphabetical order as

they are entered. In this example we would just need to change the

declaration of quotelist to sortedlist rather than hashtable

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Using Database Data

• SQL or Access database connections available.

• DataSource Controls

• Gridview (and other controls) available.

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CAM04 Database

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AccessDataSource

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Drag an

AccessDataSource

Control onto the

form and use

Configure Data

Source (from its

associated task list)

to point to the

Access database,

the relevant table

and fields.

AccessDataSource

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AccessDataSource

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AccessDataSource

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If the table is

updatable you will

have the option of

generating the

necessary Insert,

Update and Delete

SQL statements.

AccessDataSource

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The query

can be

tested to

show that

the database

connection

has been

established.

Gridview control

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From the

Gridview

tasklist we can

choose Data

Source which

will then link to

the

AccessDataSo

urce we have

created.

Gridview control

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Gridview control

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Gridview control in action

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Formating Gridview Columns

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The Columns property

of the GridView is a

collection of editable

items. We want to alter

the format of the

Release Date column.

Change it to {0:dd MMM

yyyy} – note may need

to set HTML Encode

property for this item to

False.

Formating Gridview Columns

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We now have the

date column

looking much tidier.

Formating Gridview Columns

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To get the album

images we need

to include an

image field in the

GridView table

Formating Gridview Columns

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It must be

bound to the

correct

datafield

Formating Gridview Columns

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And here is

the latest

result.

Formating Gridview Columns

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And by

adding a final

hyperlink

column we

have the final

result.

DetailsView Control

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DetailsView Control

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FormsView Control

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FormsView Control

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Tutorial

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In the tutorial this week

you will create this page.

It contains a GridView

showing all the records

from a database. When

the user clicks on the

album cover picture they

will be able to display

more details from

another page.

Do not implement other

page.!!