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Trước tiên, bạn nhìn vào theo dõi tại Chương 14. Nó là kỹ thuật của việc thêm mã vào các trang web của bạn, cho một vài lý do: cho mục đích gỡ lỗi, giá trị sản lượng của các biến, hoặc đơn giản là để tìm ra nơi trong mã của bạn những điều nào đó xảy ra. | Chapter 15 Using ASP.NET Tracing You first looked at tracing in Chapter 14. It is the technique of adding code to your pages for a few reasons for debugging purposes to output values of variables or simply to find out where in your code certain things happen. The great thing about ASP.NET tracing is that not only is it extremely simple to do but it s also easily configurable and doesn t require tracing code to be removed if you don t want the trace information shown. What s also great is that you get a wealth of additional information about the page which can be useful for both debugging purposes and for learning about ASP.NET. Tracing Individual Pages Tracing can be turned on for individual pages by adding the Trace attribute to the Page directive @ Page Trace true On its own this outputs a great deal of information about the page but you can also add your own output using the Trace class which has methods to write output to the trace log Trace.Write my information The following Try It Out shows tracing in action. Try It Out Page-Level Tracing 1. In the Wrox United application for the chapter open Checkout.aspx in Source View. 2. Add the Trace attribute to the Page directive @ Page Trace True . 3. Save the file and run the application. 4. Add some items from the shop to your shopping cart and navigate to the Checkout page where you ll see that the bottom of the page has lots of information added. You might have to scroll down the page to see all of the information. 5. Switch back to VWD and open the code file for the Checkout page. 6. At the top of the Page_Load event add the following line of code Trace.Write In Page_Load 7. Before the check to see if the user is authenticated add the following Trace.Write In page_Load User.Identity.IsAuthenticated.ToString if User.Identity.IsAuthenticated . 8. Save the page and run the application again navigating to the Checkout page. 9. Scroll the page down so you can see the Trace Information section as shown in Figure 15-6.
