Như bạn có thể thấy, nhiệm vụ đã được bổ sung vào danh sách hoạt động với TaskId của 7. TaskId là một lĩnh vực nhận dạng trong bảng chỉ đơn giản là tăng lên với mỗi bổ sung mới. Bây giờ, nếu bạn đã đánh dấu nhiệm vụ hoàn thành bằng cách nhấn vào liên kết Chỉnh sửa và sau đó kiểm tra | 150 CHAPTER 7 USING THE AJAX CONTROL TOOLKIT PART 1 Table 7-6. Properties of the CascadingDropDown Control Property Name Description Category Category name of the CascadingDropDown control LoadingText Status text shown on the control itself while the data for the drop-down is being fetched ParentControlID The ID of the other drop-down control whose selection impacts this control PromptText Text shown if the drop-down is empty ServiceMethod Name of the web method used to retrieve the data ServicePath Path of the web service used to retrieve the data TargetControlID ID of the target corresponding DropDown control You may have also seen cascading drop-downs on many car shopping searching sites in which you start with the manufacturer of the car and end up with the exact model of the car. We ll look one such example which comes with the full-source version of the AJAX Control Toolkit available for download at http . After you load the solution into Visual Studio under the SampleWebSite project locate the CascadingDropDown folder with an .aspx and .asmx page. Set as the start page and then run the application Ctrl F5 . You are presented with three drop-down controls asking you to enter the make model and color of a car. With each selection the values of the subsequent drop-down control change and the complete specs of the car are displayed see Figure 7-12 . CHAPTER 7 USING THE AJAX CONTROL TOOLKIT PART 1 151 Figure 7-12. Selecting a car using CascadingDropDown controls Let s examine the markup for this page div class demoheading CascadingDropDown Demonstration div table tr td Make td td asp DropDownList ID DropDownList1 runat server Width 170 td tr tr td Model td td asp DropDownList ID DropDownList2 runat server Width 170 td tr tr 152 CHAPTER 7 USING THE AJAX CONTROL TOOLKIT PART 1 td Color td td asp DropDownList ID DropDownList3 runat server Width 170 AutoPostBack true OnSelectedIndexChanged .
