单项选择题 You create a Web Form. The Web Form uses the FormView control to enable a user to edit a record in the database. When the user clicks the Update button on the FormView control, the application must validate that the user has entered data in all of the fields. You need to ensure that the Web Form does not update if the user has not entered data in all of the fields. Which code segment should you use?（）

单项选择题 You create a Web Form. The Web Form allows users to calculate values and display the results in a label named lblResults. You need to capture all unhandled exceptions on the Web Form through the Error event. The Error event must capture each unhandled exception and display it on the Web Form. Which code segment should you use?（）

单项选择题 You create a Web Form. The Web Form allows users to calculate values and display the results in a label named lblResults. You need to capture all unhandled exceptions on the Web Form through the Error event. The Error event must capture each unhandled exception and display it on the Web Form. Which code segment should you use?（）