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

Evjen c06.tex V2 - 01/28/2008 1:58pm Page 285 Chapter 6: Themes and Skins Next, create a standard .aspx page that uses your custom server control. Before running the page, be sure to apply the defined theme on the page using the Theme attribute in the @Page directive. 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 the HeaderText 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 from WebControl . 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 o f 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 i nformation on building your own custom server controls in Chapter 26. Figure 6-13 285 Evjen c06.tex V2 - 01/28/2008 1:58pm Page 286 Chapter 6: Themes and Skins Summary 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 .skin file or elaborate style definitions, which include not only .skin files, 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 t hem, and it can remember their choices through the APIs that are offered in ASP.NET 3.5. 286 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 287 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 t he 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, DetailsView, 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 a DataReader or a DataSet object; 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 data, you were then responsible for writing the data access code to do that. Listing 7-1 shows a typical example of a data-binding operation in ASP.NET 1.0/1.1. Evjen c07.tex V2 - 01/28/2008 2:01pm Page 288 Chapter 7: Data Binding in ASP.NET 3.5 Listing 7-1: Typical data-binding operation i n 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) o perations. Figure 7-1 Additionally, because the data source controls all derive from the Control class, you can use them much as you would any other Web Server control. For instance, you can define and control the behavior of 288 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 289 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 fro m 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 the DataSourceControl class, which is derived from Control and implements the IDataSource and IListSource interfaces. 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 .aspx page inside a Visual Studio Web site project and dragging the SqlDataSource control from the t oolbox o nto 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. 289 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 290 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 t he Northwind sample database as part of the standard installation. You can still downl oad 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 the DbProviderFactory node of the machine.config file. If you have additional providers to display in the wizard you can modify your machine.config file 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. 290 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 291 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 your web.config file to make maintenance and deployment of your application easier. This screen allows you to specify the key under which the connection information 291 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 292 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 the web.config file, it is stored in the actual .aspx page as a property of the SqlDataSource control named ConnectionString . If the provider chosen was not the SQL Data Provider, a property named ProviderName will be used to store that setting. The next step in the wizard allows you to configure the SELECT statement 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 specify WHERE clause parameters for filtering and ORDER BY settings for sorting in your query. For now, do not enter any additional WHERE or ORDER BY settings. Figure 7-4 292 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 293 Chapter 7: Data Binding in ASP.NET 3.5 Finally, the Advanced button contains two advanced options. You can have the wizard generate INSERT , UPDATE ,and DELETE statements for your data, based on the SELECT statement 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 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 a ConnectionString attribute, and what query to execute by creating a SelectCommand attribute. A little later in this chapter, you look at how to configure the SqlDataSource control to execute INSERT , UPDATE ,and DELETE commands as this data changes. Data Source Mode Property One of many important properties of the SqlDataSource control is the DataSourceMode property. This property enables you to tell the control if it should use a DataSet or a DataReader internally when retrieving the data. This is important when you are designing data-driven ASP.NET p ages. If you choose to use a DataReader , data is retrieved using what is commonly known as fire hose mode,oraforward-only, read-only cursor. This is the fastest and most efficient way to read data from your data source because a DataReader does not have the memory and processing overhead of a DataSet . But choosing to use a DataSet makes the data source control m ore 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 prope rty is to use a DataSet to retrieve data. The code in Listing 7-3 shows how to add the DataSourceMode property 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 > 293 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 294 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 the SelectParameters collection to create parameters that it can use at runtime to alter the data that is returned from a q uery. The SelectParameters collection consists of types that derive from the Parameters class. You can combine any number of parameters in the collection. The data so urce 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 t he specified control CookieParameter Uses the key value of a cookie FormParameter Uses the key value from the Forms collection QuerystringParameter Uses a key value from the QueryString collection ProfileParameter Uses a key value from the user’s profile SessionParameter Uses a key value from the current user’s session Because all the parameter controls derive from the Parameter class, they all contain several useful common properties. Some of these properties are shown in the following table. Property Description Type Allows you to strongly type the value of the parameter ConvertEmptyStringToNull Indicates the control should convert the value assigned to it to Null if it is equal to System.String.Empty DefaultValue Allows you to specify a default value for the parameter if it is evaluated as Null The code in Listing 7-4 shows an example of adding a QueryStringParameter to the SelectParameters collection of your SqlDataSource control. As you can see, the SelectCommand query has been modified to include a WHERE clause. When you run this code, the value of the query string field ID is bound to the @CustomerID placeholder in your SelectCommand , allowing you to select only those customers whose CustomerID field 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 . are offered in ASP. NET 3. 5. 286 Evjen c07.tex V2 - 01/28/2008 2:01pm Page 287 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. 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. brought into the toolbox a series of new and powerful databound controls such as the Grid- View, DetailsView, and FormView. ASP. NET 3. 5 continues to make fetching and displaying data in ASP. NET as