ASP.NET 4 Unleased - p 145 ppt

ptg 1414 CHAPTER 29 Caching Application Pages and Data </body> </html> In Listing 29.47, the SqlDataSource control includes a Selecting event handler. Because this event is raised when the data cannot be retrieved from the cache, you can use this event to determine when the data is retrieved from the cache or the database server (see Figure 29.17). FIGURE 29.17 Using Push SQL cache dependencies with a DataSource control. WARNING The page in Listing 29.47 connects to a Server database named MyMovies. You should not use Push dependencies with a Local SQL Express database. The page uses a database table named Movies, which was created with the following SQL command: CREATE TABLE Movies ( Id int IDENTITY NOT NULL, Title nvarchar(100) NOT NULL, Director nvarchar(50) NOT NULL, EntryDate datetime NOT NULL DEFAULT GetDate() ) From the Library of Wow! eBook ptg 1415 Using SQL Cache Dependencies 29 Using Push SQL Cache Dependencies with Data Caching You can use Push SQL cache dependencies when working with the Cache object. You represent a Push SQL cache dependency with an instance of the SqlCacheDependency class. For example, in the Page_Load() handler in Listing 29.48, a DataTable is added to the cache that represents the contents of the Movies database table. The DataTable displays in a GridView control. LISTING 29.48 PushSQLDataCache.aspx <%@ Page Language=”C#” Trace=”true” %> <%@ Import Namespace=”System.Data” %> <%@ Import Namespace=”System.Data.SqlClient” %> <%@ Import Namespace=”System.Web.Configuration” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”> <script runat=”server”> void Page_Load() { DataTable movies = (DataTable)Cache[“Movies”]; if (movies == null) { Trace.Warn(“Retrieving data from database”); string conString = WebConfigurationManager.ConnectionStrings[“MyMovies”].ConnectionString; SqlDataAdapter dad = new SqlDataAdapter(“SELECT Title,Director FROM dbo.Movies”, ➥conString); SqlCacheDependency sqlDepend = new SqlCacheDependency(dad.SelectCommand); movies = new DataTable(); dad.Fill(movies); Cache.Insert(“Movies”, movies, sqlDepend); } grdMovies.DataSource = movies; grdMovies.DataBind(); } </script> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <title>Push SQL Data Cache</title> </head> <body> <form id=”form1” runat=”server”> From the Library of Wow! eBook ptg 1416 CHAPTER 29 Caching Application Pages and Data <div> <asp:GridView id=”grdMovies” Runat=”server” /> </div> </form> </body> </html> An instance of the SqlCacheDependency class is created. A SqlCommand object is passed to the constructor for the SqlCacheDependency class. If the results of the SqlCommand change, the DataTable will be dropped automatically from the cache. The order of the commands here is important. You need to create the SqlCacheDependency object before you execute the command. If you call the Fill() method before you create the SqlCacheDependency object, the dependency is ignored. WARNING The page in Listing 29.48 connects to a Server database named MyMovies. You should not use Push dependencies with a Local SQL Express database. The page uses a database table named Movies, which was created with the following SQL command: CREATE TABLE Movies ( Id int IDENTITY NOT NULL, Title nvarchar(100) NOT NULL, Director nvarchar(50) NOT NULL, EntryDate datetime NOT NULL DEFAULT GetDate() ) Summary In this chapter, you learned how to improve the performance of your ASP.NET applications by taking advantage of caching. In the first part of this chapter, you learned how to use each of the different types of caching technologies supported by ASP.NET Framework. First, you learned how to use Page Output Caching to cache the entire rendered contents of a page. You learned how to create different cached versions of the same page when the page is requested with different parameters, headers, and browsers. You also learned how From the Library of Wow! eBook ptg 1417 Summary 29 to remove pages programmatically from the Page Output Cache. Finally, we discussed how you can define Cache Profiles in a web configuration file. Next, you learned how to use Partial Page Caching to apply different caching policies to different regions in a page. You learned how to use post-cache substitution to dynamically inject content into a page that has been output cached. You also learned how to use User Controls to cache different areas of a page. We also discussed how you can cache data by using the different DataSource controls. You learned how to enable caching when working with the SqlDataSource, ObjectDataSource, and XmlDataSource controls. Next, you learned how to use the Cache object to cache items programmatically. You learned how to add items to the cache with different expiration policies and dependencies. You also learned how to configure the maximum size of the cache in the web configuration file. Finally, we discussed SQL cache dependencies. You learned how to use SQL cache dependencies to reload database data in the cache automatically when the data in the under- lying database changes. You learned how to use both Polling and Push SQL cache dependencies with Page Output Caching, DataSource Caching, and the Cache object. From the Library of Wow! eBook ptg This page intentionally left blank From the Library of Wow! eBook ptg CHAPTER 30 Localizing Applications for Multiple Languages IN THIS CHAPTER . Setting the Current Culture . Using the CultureInfo Class . Creating Local Resources . Creating Global Resources . Using the Localize Control . Summary You can localize an ASP.NET website so that it supports multiple languages and cultures. For example, you might need to create both an English language and Spanish language version of the same website. One approach to localization is to simply create multiple copies of the same website and translate each copy into a different language. This was a common approach when building ASP Classic (or even ASP.NET 1.1) websites. The problem with this approach is it creates a website mainte- nance nightmare. Whenever you need to make a change to the website—no matter how simple—you must make the change in each copy of the website. When building ASP.NET applications, you do not need to create multiple copies of a website to support multiple languages. Instead, you can take advantage of resource files. A resource file contains language-specific content. For example, one resource file might contain a Spanish version of all the text in your website, and a second resource file might contain the Indonesian version of all the text in your website. In this chapter, you learn how to localize ASP.NET applications. First, you learn how to set the culture of the current page. You learn how to use both the Culture and UICulture properties. You also learn how to detect users’ preferred languages automatically through their browser settings. Next, local resources are explored. A local resource contains content scoped to a particular file such as an ASP.NET page. You learn how to use both implicit and explicit resource expressions. From the Library of Wow! eBook ptg 1420 CHAPTER 30 Localizing Applications for Multiple Languages This chapter also examines global resources, which contain content that can be used in any page within an application. For example, you can place the title of your website in a global resource file. Finally, the ASP.NET Localize control is discussed. You learn how to use this control in your pages to localize big chunks of page text. Setting the Current Culture Two main properties of the Page class have an effect on localization: . UICulture . Culture The UICulture property specifies which resource files are loaded for the page. The resource files can contain all the text content of your pages translated into a particular language. You can set this property to any standard culture name. This property is discussed in detail during the discussion of using local and global resources later in this chapter. The Culture property, on the other hand, determines how strings such as dates, numerals, and currency amounts are formatted. It also determines how values are compared and sorted. For example, by modifying the Culture property, you can display dates with language-specific month names such as January (English), Januar (German), or Enero (Spanish). Both the UICulture and Culture properties accept standard culture names for their values. Culture names follow the RFC 1766 and RFC 3066 standards maintained by the Internet Engineering Task Force (IETF). The IETF website is located at www.IETF.org. Following are some common culture names: . de-DE = German (Germany) . en-US = English (United States) . en-GB = English (United Kingdom) . es-MX = Spanish (Mexico) . id-ID = Indonesian (Indonesia) . zh-CN = Chinese (China) Each culture name consists of two parts. The first part represents the language code, and the second part represents the country/region code. If you specify a culture name and do not provide a country/region code—for example, en—you have specified something called a neutral culture. If you provide both a language code and a country/region code—for example, en-US—you have specified something called a specific culture. From the Library of Wow! eBook ptg 1421 Setting the Current Culture NOTE You c an view the cult ure names supp or ted by .NET Framewor k by looki ng up t he entr y for the CultureInfo class in the Microsoft .NET Framework SDK documentation. It’s a really long list. The Culture property must always be set to a specific culture. This makes sense because, for example, different English speakers use different currency symbols. The UICulture property, on the other hand, can be set to either a neutral or specific culture name. Text written in Canadian English is pretty much the same as text written in U.S. English. You can set the UICulture and Culture properties to the same value or different values. For example, if you create an online store, you might want to set the UICulture property to the value de-DE to display German product descriptions. However, you might want to set the Culture property to the value en-US to display product prices in U.S. currency amounts. Setting a Culture Manually You can set either the UICulture or Culture properties by using the <%@ Page %> directive. For example, the page in Listing 30.1 sets both properties to the value id-ID (Indonesian). LISTING 30.1 Bagus.aspx <%@ Page Language=”C#” Culture=”id-ID” UICulture=”id-ID” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”> <script runat=”server”> void Page_Load() { lblDate.Text = DateTime.Now.ToString(“D”); lblPrice.Text = (512.33m).ToString(“c”); } </script> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <title>Bagus</title> </head> <body> <form id=”form1” runat=”server”> <div> Today’s date is: <br /> <asp:Label 30 From the Library of Wow! eBook ptg 1422 CHAPTER 30 Localizing Applications for Multiple Languages FIGURE 30.1 Displaying a localized date and price. id=”lblDate” Runat=”server” /> <hr /> The price of the product is: <br /> <asp:Label id=”lblPrice” Runat=”server” /> </div> </form> </body> </html> The page in Listing 30.1 displays a date and a currency amount. Because the Culture property is set to the value id-ID in the <%@ Page %> directive, both the date and currency amount are formatted with Indonesian cultural conventions (see Figure 30.1). The date is displayed like this: 05 March 2010 From the Library of Wow! eBook ptg 1423 Setting the Current Culture 30 The currency amount is displayed as an Indonesian Rupiah amount like this: Rp512 NOTE Setting the Culture does not actually convert a currency amount. Setting a particular culture formats only the currency as appropriate for a particular culture. If you need to convert currency amounts, you need to use a Web service: Conversion rates change minute by minute. See, for example, www.xmethods.com. Instead of using the <%@ Page %> directive to set the Culture or UICulture properties, you can set these properties programmatically. For example, the page in Listing 30.2 enables you to select a particular culture from a drop-down list of cultures (see Figure 30.2). LISTING 30.2 SelectCulture.aspx <%@ Page Language=”C#” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”> <script runat=”server”> protected void btnSelect_Click(object sender, EventArgs e) { Culture = ddlCulture.SelectedValue; FIGURE 30.2 Selecting a culture from a DropDownList control. From the Library of Wow! eBook . GetDate() ) Summary In this chapter, you learned how to improve the performance of your ASP. NET applications by taking advantage of caching. In the first part of this chapter, you learned how to. must make the change in each copy of the website. When building ASP. NET applications, you do not need to create multiple copies of a website to support multiple languages. Instead, you can. the page in Listing 30.1 sets both properties to the value id-ID (Indonesian). LISTING 30.1 Bagus.aspx <%@ Page Language=”C#” Culture=”id-ID” UICulture=”id-ID” %> <!DOCTYPE html PUBLIC