5,3 dụng nhất thả xuống và ListBox Controls tôi thấy trong chương đầu tiên của thế nào-Để kết vào một điều khiển ListBox làm thế nào để một tập dữ liệu được tạo trong thiết kế. | Populate DropDown and ListBox Controls I saw in this chapter s first How-To how to bind a ListBox control to a dataset that was created in the design. How do I populate DropDown and ListBox controls on a Web Form using code at runtime Technique ListBoxes and DropDowns which are equivalent to ComboBoxes on Windows Forms have different properties that are used for data binding than their Windows counterparts. Besides these properties displayed in Table you also need to use the Databind method and session object to track the data table that is created for products. Table . Properties Used to Bind Columns to Controls Property Description DataTextField Column in data source to use for displaying in the DropDown or ListBox control. DataValueField Column in data source that is the lookup value. Note You can use a property called DataFormatString to format the DataTextField data for display in the ListBox or DropDown controls. Steps Open and run the Visual Basic .NET-Chapter 5 solution. From the main page click on the hyperlink with the caption How-To Populate DropDown and ListBox controls. When the Web Form loads you will see a Categories dropdown with the Beverages category selected and the products for that category in the list box with the label Products. If you click on a product the three text boxes are loaded on the right of the page see Figure . 1. Create a Web Form. Then place the controls listed in Table and seen in Figure with the following properties set. Table . Control Property Settings for Validation Controls Web Form Object Property Setting Label Text Categories DropDown ID ddCategories AutoPostBack True Label Text Products ListBox ID lstProducts AutoPostBack True Label Text Product ID Label Text Product Name Label Text Unit Price TextBox ID txtProductID BackColor Transparent TextBox ID txtProductName BackColor Transparent TextBox ID txtUnitPrice BackColor Transparent HyperLink ID hplReturnToMain NavigateURL 2. As
