单项选择题 You recently developed a Web application that accesses an external Web service to retrieve current exchange rates for Certkiller .coms e-Commerce Web site. The Web service converts USD prices to the customers local currency. You have stored the URL to the external Web services endpoint in the section of the Web.config file. The Web application has been successfully deployed to a Certkiller .com Web server named Certkiller -SR14. A few months later the vendor of the Web service changes the port that is used to access the Web service. You need to update the section of the Web applications Web.config file from Certkiller -WS528. You need to ensure that your solution has a minimal impact on customers that may be connected to the e-Commerce Web site. What should you do?（）

单项选择题 ou are developing a chat forum for the Certkiller .com Web site. You are using ASP.NET 2.0 to develop the chat forum. You are developing a Web Form that allows a subscriber to alter enter their account details. The page contains the following code snippet. You need to programmatically hide the TextBox control based on other input. What should you do?（）

单项选择题 You are developing a page named Products.aspx in a Web application that contains three DropDownList controls that are dynamically loaded from a SQL Server 2005 database file. The DropDownList controls represent a vendor list, a certification list, and an exam list. Certkiller .com customers use the Products.aspx page to select exams related to particular certifications on offer from a particular vendor. A Go button initiates the selection. Each DropDownList control has an associated RequiredFieldValidator control.Whenever the customer selects a vendor, and the vendor offers certifications, then the customer must also select a certification if the. If the vendor only offers exams and not certifications, the certification list should remain hidden. Whenever the customer selects a certification, the customer must also select an exam. Validation error messages should only be displayed when the Go button is clicked. You need to set properties on the vendor DropDownList control. What should you do?（）