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A DropDownList is also commonly known as combo box. It can contain multiple data members, but unlike a normal list box the users can choose only one value from this control. Though the functionality of this DropDownList is much like a Single Row Select List Box, a DropDownList can save a lot of GUI space as it is rendered on a Single line and is expanded only when the user clicks on the Control.
This DropDownList is provided as a Server Control in ASP .Net like many other controls. This DropDownList can be used to add data manually or even for dynamic binding with data base.
A simple declaration for DropDownList can be done as below.
<asp:DropDownList ID="DropDownList1" runat="server" Height="47px" Width="73px"> </asp:DropDownList>
Properties
Property | Description |
BorderColor | enables to get or set the border color of the web server control. [Not Applicable] |
BorderStyle | enables to get or set the border style of the control. [Not Applicable] |
BorderWidth | enables to get or set the border width for the control.[Not Applicable] |
SelectedIndex | enables to get or set an Integer value to specify the zero-based index for the currently selected list item. |
AppendDataBoundItems | enables to get or set a Boolean value to indicate whether to clear the list items before binding the data to the control. |
AutoPostBack | enables to get or set a Boolean value that indicates whether to postback the web page when list item of DropDownList control is clicked. |
DataTextField | enables to get or set the name of the data source field that provides the text for the list items. |
DataTextFormatString | enables to get or set the string formatting to control the text of each list item that is to be displayed. |
DataValueField | enables to get or set the name of the data source field that provides the value for the list items. |
Items | enables to manage the list items of the DropDownList control. |
SelectedItem | enables to get the currently selected list item in DropDownList control. |
SelectedValue | enables to get the value property of selected list item that returns ListItem object. |
Text | enables to get or set the text for the control. |
ValidationGroup | enables to get or set the name of the group of controls to which it belongs to and causes validation when posts back to the server. |
DataMember | enables to get or set the name of the list of data that the data-bound control binds to. The list of data items may have more than one data members. |
DataSourceID | enables to get or set the ID of the DataSource control from which the data-bound control retrieves its list of data items. |
DataSourceObject | enables to get an object that implements the IDataSource interface and provides the access to the data items. |
DataSource | enables to get or set the object from which the data-bound control retrieves its list of data items. |
CausesValidation | enables to get or set a Boolean value to indicate whether to perform the validation when any list item of the control is clicked. |
Events
SelectedIndexChanged: Occurs when selected item of list control changes between postbacks to the server.
TextChanged: Occurs when Text and SelectedValue properties change between postbacks to the server.
Example

.CS Code
protected void Page_Load(object sender, EventArgs e) { if (!Page.IsPostBack) { DropDownList1.Items.Add("pototo"); DropDownList1.Items.Add("Tamato"); DropDownList1.Items.Add("brinjal"); DropDownList1.Items.Add("Lime"); DropDownList1.Items.Add("Pea"); /////////////////////////////////////////////// DropDownList2.Items.Add("Jeans"); DropDownList2.Items.Add("Shirt"); DropDownList2.Items.Add("Cap"); DropDownList2.Items.Add("Blaser"); DropDownList2.Items.Add("Tie"); ////////////////////////////////////////////////// DropDownList3.Items.Add("Lather"); DropDownList3.Items.Add("Canvas"); DropDownList3.Items.Add("Sports"); DropDownList3.Items.Add("Sandle"); DropDownList3.Items.Add("Sleeper"); ///////////////////////////////////////////// DropDownList4.Items.Add("Fan"); DropDownList4.Items.Add("TybeLight"); DropDownList4.Items.Add("Plug"); DropDownList4.Items.Add("Holder"); DropDownList4.Items.Add("Wire"); } protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) { ListBox1.Items.Add("Vegitables:" + DropDownList1.SelectedItem.Text); //DropDownList1.Items.Clear(); } protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e) { } protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e) { ListBox1.Items.Add("Cloths:" + DropDownList2.SelectedItem.Text); } protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e) { ListBox1.Items.Add("Showes:" + DropDownList3.SelectedItem.Text); } protected void DropDownList4_SelectedIndexChanged(object sender, EventArgs e) { ListBox1.Items.Add("Electronics:" + DropDownList4.SelectedItem.Text); }
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