Professional ASP.NET 3.5 in C# and Visual Basic Part 34 pps

ASP.NET 3.5 continues to make fetching and displaying data in ASP.NET as simple as possible by introducing the LinqDataSource control and the ListView control This chapter explores all t

Chapter 6: Themes and Skins

Next, create a standard.aspxpage that uses your custom server control Before running the page, be sure

to apply the defined theme on the page using theThemeattribute in the@Pagedirective With everything

in place, running the page produces the following results in the browser:

FROM THE SKIN FILE

This value, which was specified in the skin file, is displayed no matter what you apply as theHeaderText value in the server control

In addition to changing values of custom properties that are contained in server control, you can also

change the inherited properties that come fromWebControl For instance, you can change settings in

your skin file as shown in Listing 6-17

Listing 6-17: Changing inherited properties in the custom control

<%@ Register Assembly="ControlForThemes" Namespace="ControlForThemes"

TagPrefix="cc1" %>

<cc1:webcustomcontrol1 runat="server" BackColor="Gray" />

With this in place, you have changed one of the inherited properties from the skin file This setting

changes the background color of the server control to gray (even if it is set to something else in the

control itself) The result is presented in Figure 6-13

You can find more information on building your own custom server controls in Chapter 26.

Figure 6-13

Chapter 6: Themes and Skins

Summar y

With the availability of themes and skins in ASP.NET 3.5, it is quite easy to apply a consistent look

and feel across your entire application Remember that themes can contain only simple server control

definitions in a.skinfile or elaborate style definitions, which include not only.skinfiles, but also CSS

style definitions and even images!

As you will see later in the book, you can use themes in conjunction with the personalization features

that ASP.NET provides This enables your end users to customize their experiences by selecting their

own themes Your application can present a theme just for them, and it can remember their choices

through the APIs that are offered in ASP.NET 3.5

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Data Binding

in ASP.NET 3.5

One of the most exciting features of ASP.NET 1.0/1.1 was its capability to bind entire collections

of data to controls at runtime without requiring you to write large amounts of code The controls

understood they were data-bound and would render the appropriate HTML for each item in the

data collection Additionally, you could bind the controls to any type of data sources, from simple

arrays to complex Oracle database query results This was a huge step forward from ASP, in which

each developer was responsible for writing all the data access code, looping through a recordset,

and manually rendering the appropriate HTML code for each record of data

In ASP.NET 2.0, Microsoft took the concept of data binding and expanded it to make it even easier

to understand and use by introducing a new layer of data abstraction called data source controls

It also brought into the toolbox a series of new and powerful databound controls such as the

Grid-View, DetailsGrid-View, and FormView ASP.NET 3.5 continues to make fetching and displaying data in

ASP.NET as simple as possible by introducing the LinqDataSource control and the ListView control

This chapter explores all the provided data source controls, and describes other data-binding

features in ASP.NET It shows how you can use the data source controls to easily and quickly bind

data to data-bound controls It also focuses on the power of the data-bound list controls included in

ASP.NET 3.5, such as the GridView, DetailsView, FormView, and the new ListView control Finally,

you take a look at changes in the inline data binding syntax and inline XML data binding

Data Source Controls

In ASP.NET 1.0/1.1, you typically performed a data-binding operation by writing some data access

code to retrieve aDataReaderor aDataSetobject; then you bound that data object to a server

control such as a DataGrid, DropDownList, or ListBox If you wanted to update or delete the bound

Chapter 7: Data Binding in ASP.NET 3.5

Listing 7-1: Typical data-binding operation in ASP.NET 1.0/1.1

VB

Dim conn As New SqlConnection()

Dim cmd As New SqlCommand("SELECT * FROM Customers", conn)

Dim da As New SqlDataAdapter(cmd)

Dim ds As New DataSet()

da.Fill(ds)

DataGrid1.DataSource = ds

DataGrid1.DataBind()

C#

SqlConnection conn = new SqlConnection();

SqlCommand cmd = new SqlCommand("SELECT * FROM Customers", conn);

SqlDataAdapter da = new SqlDataAdapter(cmd);

DataSet ds = new DataSet();

da.Fill(ds);

DataGrid1.DataSource = ds;

DataGrid1.DataBind();

ASP.NET 2.0 introduced an additional layer of abstraction through the use of data source controls As

shown in Figure 7-1, these controls abstract the use of an underlying data provider, such as the SQL Data

Provider or the OLE DB Data Provider This means you no longer need to concern yourself with the hows

and whys of using the data providers Instead, the data source controls do all the heavy lifting for you

You need to know only where your data is and, if necessary, how to construct a query for performing

CRUD (Create, Retrieve, Update, and Delete) operations

Figure 7-1

Additionally, because the data source controls all derive from theControlclass, you can use them much

as you would any other Web Server control For instance, you can define and control the behavior of

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Chapter 7: Data Binding in ASP.NET 3.5

the data source control either declaratively in your HTML or programmatically This means you can

perform all manner of data access and manipulation without ever having to write one line of code In

fact, although you certainly can control the data source controls from code, the samples in this chapter

show you how to perform powerful database queries using nothing more than the Visual Studio 2008

wizards and declarative syntax

The six built-in data source controls in ASP.NET 3.5 are each used for a specific type of data access The following table lists and describes each data source control

Control Name Description

SqlDataSource control Provides access to any data source that has an ADO.NET Data

Provider available; by default, the control has access to the ODBC, OLE DB, SQL Server, Oracle, and SQL Server CE providers

LinqDataSource control Provides access to different types of data objects using LINQ queries ObjectDataSource control Provides specialized data access to business objects or other classes

that return data

XmlDataSource control Provides specialized data access to XML documents, either

physically or in-memory

SiteMapDataSource control Provides specialized access to site map data for a Web site that is

stored by the site map provider

AccessDataSource control Provides specialized access to Access databases

All the data source controls are derived from theDataSourceControlclass, which is derived from

Controland implements theIDataSourceandIListSourceinterfaces This means that although each

control is designed for use with specific data sources, all data source controls share a basic set of core

functionality It also means that it is easy for you to create your own custom data source controls based

on the structure of your specific data sources

SqlDataSource Control

The SqlDataSource control is the data source control to use if your data is stored in a SQL Server, SQL

Server Express, Oracle Server, ODBC data source, OLE DB data source, or Windows SQL CE Database The control provides an easy-to-use wizard that walks you through the configuration process, or you can modify the control manually by changing the control attributes directly in Source view In the example presented in this section, you walk through creating a SqlDataSource control and configuring it using the wizard After you complete the configuration, you examine the source code it generates

Begin using the control by opening an.aspxpage inside a Visual Studio Web site project and dragging the SqlDataSource control from the toolbox onto the form The Visual Studio toolbox has been divided

into functional groups so you find all the data-related controls located under the Data section

Configuring a Data Connection

After the control has been dropped onto the Web page, you tell it what connection it should use The

easiest way to do this is by using the Configure Data Source Wizard, shown in Figure 7-2 Launch this

wizard by selecting the Configure Data Source option from the data source control’s smart tag menu

Chapter 7: Data Binding in ASP.NET 3.5

Figure 7-2

Once the wizard opens, you should create a connection to the Northwind database in SQL You will use

this connection for most of the demonstrations in this chapter

Beginning with Microsoft SQL Server 2005, Microsoft no longer includes the Northwind sample database

as part of the standard installation You can still download the installation scripts for the sample

database from the following location:

http://www.microsoft.com/downloads/details.aspx?FamilyId=06616212-0356-46A0-8DA2-EEBC53A68034&displaylang=en

After the wizard opens, you can select an existing connection from the drop-down list or create a new

connection If you click the New Connection button, the Connection Properties dialog, shown in

Figure 7-3, appears From here, you can set all the properties of a new database connection

Click the Change button From here, you can choose the specific data provider you want this connection

to use By default, the control uses the ADO.NET SQL Data Provider; also available are Oracle, OLE DB,

ODBC, and SQL Server Mobile Edition providers

The list of providers is generated from the data contained in theDbProviderFactorynode of the

machine.configfile If you have additional providers to display in the wizard you can modify

yourmachine.configfile to include specific providers’ information.

Next, simply fill in the appropriate information for your database connection Click the Test Connection

button to verify that your connection information is correct, and then click OK to return to the wizard

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Chapter 7: Data Binding in ASP.NET 3.5

Figure 7-3

After you have returned to the Data Source Configuration Wizard, notice that the connection you

cre-ated is listed in the available connections drop-down list After you select a connection string from the

drop-down, the connection information shows in the Data Connection info area This allows you to easily review the connection information for the Connection selected in the drop-down list

Click the Next button to continue through the wizard The next step allows you to choose to have the wiz-ard save your connection information in yourweb.configfile to make maintenance and deployment of your application easier This screen allows you to specify the key under which the connection information

Chapter 7: Data Binding in ASP.NET 3.5

should be stored in the configuration file Should you choose not to store your connection information

in theweb.configfile, it is stored in the actual.aspxpage as a property of theSqlDataSourcecontrol

namedConnectionString If the provider chosen was not the SQL Data Provider, a property named

ProviderNamewill be used to store that setting

The next step in the wizard allows you to configure theSELECTstatement your data source control will

use to retrieve data from the database This screen, shown in Figure 7-4, gives you a drop-down list of all

the tables and views available in the database that you specified in your connection information After

you select a table or view, the list box allows you to select the column you want to include in the

query You can select all columns available using an asterisk (*), or you can choose specific columns by

marking the check box located next to each column name By clicking the WHERE or ORDER BY button,

it is also possible to specifyWHEREclause parameters for filtering andORDER BYsettings for sorting in your

query For now, do not enter any additionalWHEREorORDER BYsettings

Figure 7-4

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Chapter 7: Data Binding in ASP.NET 3.5

Finally, the Advanced button contains two advanced options You can have the wizard generateINSERT, UPDATE, andDELETEstatements for your data, based on theSELECTstatement you created You can

also configure the data source control to use Optimistic Concurrency to prevent data concurrency issues Optimistic Concurrency is a database technique that can help you prevent the accidental overwriting

of data When Optimistic Concurrency is enabled, the Update and Delete SQL statements used by the

SqlDataSource control are modified so that they include both the original and updated values When the queries are executed, the data in the targeted record is compated to the SqlDataSource controls original values and if a difference is found,indicating that the data has changed since it was originally reterived

by the SqlDataSource control, the Update or Delete will not occur

The final screen of the wizard allows you to preview the data selected by your data source control to

verify the query is working as you expect it to Simply click the Finish button to complete the wizard

When you are done configuring your data connection, you can see exactly what the configured SqlData-Source control looks like Change to SqlData-Source view in Visual Studio to see how the wizard has generated the appropriate attributes for your control It should look something like the code in Listing 7-2

Listing 7-2: Typical SqlDataSource control generated by Visual Studio

<asp:SqlDataSource ID="SqlDataSource1" Runat="server"

SelectCommand="SELECT * FROM [Customers]"

ConnectionString="<%$ ConnectionStrings:AppConnectionString1 %>">

</asp:SqlDataSource>

You can see that the control uses a declarative syntax to configure which connection it should use by

creating aConnectionStringattribute, and what query to execute by creating aSelectCommandattribute

A little later in this chapter, you look at how to configure theSqlDataSourcecontrol to executeINSERT, UPDATE, andDELETEcommands as this data changes

Data Source Mode Property

One of many important properties of the SqlDataSource control is theDataSourceModeproperty This

property enables you to tell the control if it should use aDataSetor aDataReaderinternally when

retrieving the data This is important when you are designing data-driven ASP.NET pages If you choose

to use aDataReader, data is retrieved using what is commonly known as fire hose mode, or a forward-only,

read-only cursor This is the fastest and most efficient way to read data from your data source because

aDataReaderdoes not have the memory and processing overhead of aDataSet But choosing to use a

DataSetmakes the data source control more powerful by enabling the control to perform other

opera-tions such as filtering, sorting, and paging It also enables the built-in caching capabilities of the control Each option offers distinct advantages and disadvantages, so consider this property carefully when

designing your Web site The default value for this property is to use aDataSetto retrieve data The

code in Listing 7-3 shows how to add theDataSourceModeproperty to your SqlDataSource control

Listing 7-3: Adding the DataSourceMode property to a SqlDataSource control

<asp:SqlDataSource ID="SqlDataSource1" Runat="server"

SelectCommand="SELECT * FROM [Customers]"

ConnectionString="<%$ ConnectionStrings:AppConnectionString1 %>"

DataSourceMode="DataSet">

</asp:SqlDataSource>

Chapter 7: Data Binding in ASP.NET 3.5

Filtering Data Using SelectParameters

Of course, when selecting data from your data source, you may not want to get every single row of data

from a view or table You want to be able to specify parameters in your query to limit the data that is

returned The data source control allows you to do this by using theSelectParameterscollection to

create parameters that it can use at runtime to alter the data that is returned from a query

TheSelectParameterscollection consists of types that derive from theParametersclass You can

combine any number of parameters in the collection The data source control then uses these to create a

dynamic SQL query The following table lists and describes the available parameter types

Parameter Description

ControlParameter Uses the value of a property of the specified control

QuerystringParameter Uses a key value from the QueryString collection

SessionParameter Uses a key value from the current user’s session

Because all the parameter controls derive from theParameterclass, they all contain several useful

common properties Some of these properties are shown in the following table

Property Description

ConvertEmptyStringToNull Indicates the control should convert the value assigned to it toNull

if it is equal toSystem.String.Empty DefaultValue Allows you to specify a default value for the parameter if it is

evaluated asNull

The code in Listing 7-4 shows an example of adding a QueryStringParameter to theSelectParameters

collection of your SqlDataSource control As you can see, theSelectCommandquery has been modified

to include aWHEREclause When you run this code, the value of the query string fieldIDis bound to the

@CustomerIDplaceholder in yourSelectCommand, allowing you to select only those customers whose

CustomerIDfield matches the value of the query string field

Listing 7-4: Filtering select data using SelectParameter controls

<asp:SqlDataSource ID="SqlDataSource1" Runat="server"

SelectCommand="SELECT * FROM [Customers] WHERE ([CustomerID] = @CustomerID)"

ConnectionString="<%$ ConnectionStrings:AppConnectionString1 %>"

DataSourceMode="DataSet">

294