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Using the DropDownList Control
The DropDownList control in ASP.NET is used to display a list of items where the user can select one option. It is similar to the RadioButtonList control, but with a drop-down interface.
To add a DropDownList control to an ASP.NET page, you can drag and drop the control from the Toolbox onto the page in Design view. You can then set the properties of the control, such as the items to display, the default selection, and whether the control allows multiple selections.
One common use of the DropDownList control is to allow the user to select from a list of options that are stored in a database. You can use data binding to populate the items in the DropDownList control from a data source, such as a SQL Server database or an XML file.
To bind data to a DropDownList control, you can set the DataSource property to the data source and the DataTextField and DataValueField properties to the names of the fields in the data source that contain the text and value of each item. You can then call the DataBind method to populate the control with the items from the data source.
When the user selects an item in the DropDownList control, you can handle the SelectedIndexChanged event to perform some action based on the selected item. For example, you might update a label on the page to display information about the selected item or redirect the user to a different page based on their selection.
The ASP.NET DropDownList control displays a large number of items in a very little space because it drops down to display its list when the user clicks the arrow.
At design-time, you can add static items to the DropDownList control by using the ListItem collection editor. At runtime, you can fill a DropDownList control with almost any data as long as you can get it into a simple list. To put color names in a DropDownList control, follow these steps
- From the Toolbox, add a DropDownList, Label, and Panel control to an ASP.NET page.
- Select the DropDownList control and set its AutoPostBack property to True.
AutoPostBack causes a page to submit its data to the Web server when the user merely selects a different item. No Submit button is required.
- Double-click the DropDownList control to create its default event handler and use the following code inside the SelectedIndexChanged subroutine:
String strClr =””;
strClr = DropDownList1.SelectedValue;
System.Drawing.Color objColor;
objColor = System.Drawing.ColorTranslator.FromHtml(strClr);
Panel1.BackColor = objColor;
Label1.Text = strClr;
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