ListItem Class
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ListItem Class

 

Represents a data item in a data-bound list control. This class cannot be inherited.

Namespace:   System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

System.Object
  System.Web.UI.WebControls.ListItem

[TypeConverterAttribute(typeof(ExpandableObjectConverter))]
public sealed class ListItem : IStateManager, IParserAccessor, 
	IAttributeAccessor

NameDescription
System_CAPS_pubmethodListItem()

Initializes a new instance of the ListItem class.

System_CAPS_pubmethodListItem(String)

Initializes a new instance of the ListItem class with the specified text data.

System_CAPS_pubmethodListItem(String, String)

Initializes a new instance of the ListItem class with the specified text and value data.

System_CAPS_pubmethodListItem(String, String, Boolean)

Initializes a new instance of the ListItem class with the specified text, value, and enabled data.

NameDescription
System_CAPS_pubpropertyAttributes

Gets a collection of attribute name and value pairs for the ListItem that are not directly supported by the class.

System_CAPS_pubpropertyEnabled

Gets or sets a value indicating whether the list item is enabled.

System_CAPS_pubpropertySelected

Gets or sets a value indicating whether the item is selected.

System_CAPS_pubpropertyText

Gets or sets the text displayed in a list control for the item represented by the ListItem.

System_CAPS_pubpropertyValue

Gets or sets the value associated with the ListItem.

NameDescription
System_CAPS_pubmethodEquals(Object)

Determines whether the specified object has the same value and text as the current list item.(Overrides Object.Equals(Object).)

System_CAPS_pubmethodSystem_CAPS_staticFromString(String)

Creates a ListItem from the specified text.

System_CAPS_pubmethodGetHashCode()

Serves as a hash function for a particular type, and is suitable for use in hashing algorithms and data structures like a hash table.(Overrides Object.GetHashCode().)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Overrides Object.ToString().)

NameDescription
System_CAPS_pubinterfaceSystem_CAPS_privmethodIAttributeAccessor.GetAttribute(String)

This API supports the product infrastructure and is not intended to be used directly from your code. Returns the attribute value of the list item control having the specified attribute name.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIAttributeAccessor.SetAttribute(String, String)

This API supports the product infrastructure and is not intended to be used directly from your code. Sets an attribute of the list item control with the specified name and value.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIParserAccessor.AddParsedSubObject(Object)

This API supports the product infrastructure and is not intended to be used directly from your code. Allows the Text property to be persisted as inner content.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIStateManager.LoadViewState(Object)

This API supports the product infrastructure and is not intended to be used directly from your code. For a description of this member, see IStateManager.LoadViewState.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIStateManager.SaveViewState()

This API supports the product infrastructure and is not intended to be used directly from your code. For a description of this member, see IStateManager.SaveViewState.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIStateManager.TrackViewState()

This API supports the product infrastructure and is not intended to be used directly from your code. For a description of this member, see IStateManager.TrackViewState.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyIStateManager.IsTrackingViewState

This API supports the product infrastructure and is not intended to be used directly from your code. For a description of this member, see IStateManager.IsTrackingViewState.

A ListItem control represents an individual data item within a data-bound list control, such as a ListBox or a RadioButtonList control.

There are several ways to specify the text displayed for an item in the list control. The most common method is by placing text in the inner HTML content. The inner HTML content is the text between the opening and closing tags of the ListItem control. You can also use the Text property to specify the text displayed in the list control for the item.

The Value property allows you to associate a value with the item in the list control, in addition to the text displayed in the control. For example, you can display text for an item in the list control, such as "Item 1", and use the Value property to specify a value for that item, such as "$1.99".

You can have any combination of the inner HTML content, Text, or Value properties set. The resulting HTML output for the ListItem control depends on the combination of these three properties that are set. For example, if all three properties are set as follows:

<asp:ListItem Value="Value 1" Text="Item 1">Inner 1</asp:ListItem>

The inner HTML content is used for rendered inner HTML content and the Value property is used for the Value attribute. The resulting HTML rendering output is:

<option value="Value 1">Inner 1</option>

The following table lists the combination of set properties and the corresponding property used for the rendered inner HTML content and Value attribute. The three columns on the left list the combination of set properties. The two columns on the right list which property value is used for the corresponding attribute.

Inner HTML content

Text property

Value property

Rendered Inner HTML content

Rendered Value attribute

Set

Set

Set

Inner HTML content

Value property

Set

Set

Not set

Inner HTML content

Inner HTML content

Set

Not set

Set

Inner HTML content

Value property

Set

Not set

Not set

Inner HTML content

Inner HTML text

Not set

Set

Set

Text property

Value property

Not set

Set

Not set

Text property

Text property

Not set

Not set

Set

Value property

Value property

Not set

Not set

Not set

Not set

Not set

System_CAPS_noteNote

Because the Text and Value properties each have a default value of an empty string, it is possible to have empty list items in the list control.

When a list control is displayed, any ListItem control with its Selected property set to true appears highlighted in the control.

The ListItem control provides the Enabled property to allow you to specify whether a ListItem control is enabled or disabled. A ListItem control that is disabled is dimmed to indicate that it cannot be selected. Use this property to disable a ListItem control in either a RadioButtonList control or a CheckBoxList control.

System_CAPS_noteNote

You cannot use this property to disable a ListItem control in a DropDownList control or ListBox control.

For a list of initial property values for an instance of ListItem, see the ListItem constructor.

System_CAPS_cautionCaution

This control can be used to display user input, which might include malicious client script. Check any information that is sent from a client for executable script, SQL statements, or other code before displaying it in your application. You can use validation controls to verify user input before displaying the input text in a control. ASP.NET provides an input request validation feature to block script and HTML in user input. For more information, see Securing Standard ControlsHow to: Protect Against Script Exploits in a Web Application by Applying HTML Encoding to Strings, and Validating User Input in ASP.NET Web Pages.

The following example illustrates the use of ListItem controls within a ListBox control.

System_CAPS_noteNote

The following code samples use the single-file code model and may not work correctly if copied directly into a code-behind file. Each code sample must be copied into an empty text file that has an .aspx extension. For more information on the Web Forms code model, see ASP.NET Web Forms Page Code Model.

<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
 <head>
    <title>ListBox Example</title>
<script language="C#" runat="server">

         void SubmitBtn_Click(Object Sender, EventArgs e) {
             if (ListBox1.SelectedIndex > -1) {
                 Label1.Text="You chose: " + ListBox1.SelectedItem.Text;
                 Label1.Text+="<br /> with value: " + ListBox1.SelectedItem.Value;
             }
         }

     </script>

 </head>
 <body>

     <h3>ListBox Example</h3>
     <br />

     <form id="form1" runat="server">

         <asp:ListBox id="ListBox1" Width="100px" runat="server">
             <asp:ListItem>Item 1</asp:ListItem>
             <asp:ListItem>Item 2</asp:ListItem>
             <asp:ListItem>Item 3</asp:ListItem>
             <asp:ListItem Value="Value 4">Item 4</asp:ListItem>
             <asp:ListItem Text="Item 5" Value="Value 5" Selected="True"/>
             <asp:ListItem>Item 6</asp:ListItem>
         </asp:ListBox>

         <asp:button Text="Submit" OnClick="SubmitBtn_Click" runat="server" />

         <br />

         <asp:Label id="Label1" font-names="Verdana" font-size="10pt" runat="server"/>

     </form>

 </body>
 </html>

<!-- This example demonstrates how to select multiple items from a DataList and add the 
selected items to a DataGrid. The example uses a foreach loop to iterate through 
the ListItem objects in the ListItemCollection of ListBox1. -->

<%@ Page language="c#" AutoEventWireup="true"%>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script language="C#" runat="server">
            // Global Variables.
            private DataView dv;
            private DataTable dt = new DataTable();

            private void Page_Load(object sender, System.EventArgs e)
            {
                // Set the number of rows displayed in the ListBox to be
                // the number of items in the ListBoxCollection.
                ListBox1.Rows = ListBox1.Items.Count;

                // If the DataTable is already stored in the Web form's default
                // HttpSessionState variable, then don't recreate the DataTable.
                if (Session["data"] == null)
                {
                    // Add columns to the DataTable.
                    dt.Columns.Add(new DataColumn("Item"));
                    dt.Columns.Add(new DataColumn("Price"));
            // Store the DataTable in the Session variable so it can 
                    // be accessed again later.
                    Session["data"] = dt;

                    // Use the table to create a DataView, because the DataGrid
                    // can only bind to a data source that implements IEnumerable.
                    dv = new DataView(dt);

                    // Set the DataView as the data source, and bind it to the DataGrid.
                    DataGrid1.DataSource = dv;
                    DataGrid1.DataBind();
                }
            }

            private void addButton_Click(object sender, System.EventArgs e)
            {
                // Add the items selected in ListBox1 to DataGrid1.
                foreach (ListItem item in ListBox1.Items)
                {
                    if (item.Selected)
                    {
                        // Add the item to the DataGrid.
                        // First, get the DataTable from the Session variable.
                        dt = (DataTable)Session["data"];

                        if (dt != null)
                        { 
                            // Create a new DataRow in the DataTable.
                            DataRow dr = dt.NewRow();
                            // Add the item to the new DataRow.
                            dr["Item"] = item.Text;
                            // Add the item's value to the DataRow.
                            dr["Price"] = item.Value;
                            // Add the DataRow to the DataTable.
                            dt.Rows.Add(dr);

                            // Rebind the data to DataGrid1.
                            dv = new DataView(dt);
                            DataGrid1.DataSource = dv;
                            DataGrid1.DataBind();
                        }
                    }
                }
            }
        </script>
<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
    <title> ListItemCollection Example </title>
</head>

    <body>
        <form id="form1" runat="server">

            <h3> ListItemCollection Example </h3>

            <table cellpadding="6" border="0">
                <tr>
                    <td valign="top">
                        <asp:ListBox id="ListBox1" runat="server" SelectionMode="Multiple">
                            <asp:ListItem Value=".89">apples</asp:ListItem>
                            <asp:ListItem Value=".49">bananas</asp:ListItem>
                            <asp:ListItem Value="2.99">cherries</asp:ListItem>
                            <asp:ListItem Value="1.49">grapes</asp:ListItem>
                            <asp:ListItem Value="2.00">mangos</asp:ListItem>
                            <asp:ListItem Value="1.09">oranges</asp:ListItem>
                        </asp:ListBox>
                    </td>

                    <td valign="top">
                        <asp:Button id="addButton" runat="server" Text="Add -->"
                            Width="100px" OnClick="addButton_Click"></asp:Button>
                    </td>

                    <td valign="top">
                        <asp:DataGrid Runat="server" ID="DataGrid1" CellPadding="4">
                        </asp:DataGrid>
                    </td>
                </tr>
            </table>        
        </form>
    </body>
</html>

.NET Framework
Available since 1.1

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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