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ListItemCollection Class

A collection of ListItem objects in a list control. This class cannot be inherited.

System.Object
  System.Web.UI.WebControls.ListItemCollection

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

'Declaration
Public NotInheritable Class ListItemCollection _
	Implements ICollection, IEnumerable, IList, IStateManager

The ListItemCollection type exposes the following members.

  NameDescription
Public methodListItemCollectionInitializes a new instance of the ListItemCollection class.
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  NameDescription
Public propertyCapacityGets or sets the maximum number of items that the ListItemCollection can store.
Public propertyCountGets the number of ListItem objects in the collection.
Public propertyIsReadOnlyGets a value indicating whether the ListItemCollection is read-only.
Public propertyIsSynchronizedGets a value indicating whether access to the ListItemCollection is synchronized (thread-safe).
Public propertyItemGets a ListItem at the specified index in the collection.
Public propertySyncRootGets the object that can be used to synchronize access to the ListItemCollection.
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  NameDescription
Public methodAdd(ListItem)Appends the specified ListItem to the end of the collection.
Public methodAdd(String)Appends a ListItem to the end of the collection that represents the specified string.
Public methodAddRangeAdds the items in an array of ListItem objects to the collection.
Public methodClearRemoves all ListItem objects from the collection.
Public methodContainsDetermines whether the collection contains the specified item.
Public methodCopyToCopies the items from the ListItemCollection to the specified System.Array, starting with the specified index.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodFindByTextSearches the collection for a ListItem with a Text property that equals the specified text.
Public methodFindByValueSearches the collection for a ListItem with a Value property that contains the specified value.
Public methodGetEnumeratorReturns a System.Collections.IEnumerator implemented object that contains all ListItem objects in the ListItemCollection.
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIndexOfDetermines the index value that represents the position of the specified ListItem in the collection.
Public methodInsert(Int32, String)Inserts a ListItem which represents the specified string in the collection at the specified index location.
Public methodInsert(Int32, ListItem)Inserts the specified ListItem in the collection at the specified index location.
Public methodRemove(ListItem)Removes the specified ListItem from the collection.
Public methodRemove(String)Removes a ListItem from the collection that represents the specified string.
Public methodRemoveAtRemoves the ListItem at the specified index from the collection.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Public Extension MethodAsParallelOverloaded. Enables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension MethodAsParallelOverloaded. (Defined by ParallelEnumerable.)
Public Extension MethodAsQueryableOverloaded. Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension MethodAsQueryableOverloaded. (Defined by Queryable.)
Public Extension MethodCast(Of TResult)Overloaded. Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension MethodCast(Of TResult)Overloaded. (Defined by Enumerable.)
Public Extension MethodOfType(Of TResult)Overloaded. Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
Public Extension MethodOfType(Of TResult)Overloaded. (Defined by Enumerable.)
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  NameDescription
Explicit interface implemetationPrivate methodIList.AddInfrastructure. For a description of this member, see Add.
Explicit interface implemetationPrivate methodIList.ContainsInfrastructure. For a description of this member, see Contains.
Explicit interface implemetationPrivate methodIList.IndexOfInfrastructure. For a description of this member, see IndexOf.
Explicit interface implemetationPrivate methodIList.InsertInfrastructure. For a description of this member, see Insert.
Explicit interface implemetationPrivate propertyIList.IsFixedSizeInfrastructure. For a description of this member, see IsFixedSize.
Explicit interface implemetationPrivate propertyIList.ItemInfrastructure. For a description of this member, see Item.
Explicit interface implemetationPrivate methodIList.RemoveInfrastructure. For a description of this member, see Remove.
Explicit interface implemetationPrivate propertyIStateManager.IsTrackingViewStateInfrastructure. For a description of this member, see IsTrackingViewState.
Explicit interface implemetationPrivate methodIStateManager.LoadViewStateInfrastructure. Loads the previously saved state.
Explicit interface implemetationPrivate methodIStateManager.SaveViewStateInfrastructure. Returns object containing state changes.
Explicit interface implemetationPrivate methodIStateManager.TrackViewStateInfrastructure. Starts tracking state of changes.
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The ListItemCollection class represents a collection of ListItem objects. The ListItem objects, in turn, represent the items displayed in list controls, such as the ListBox. To programmatically retrieve ListItem objects from a list control, use one of following methods:

  • Use the indexer to get a single ListItem from the collection, using array notation.

  • Use the CopyTo method to copy the contents of the collection to a System.Array object, which can then be used to get items from the collection.

  • Use the GetEnumerator method to create a System.Collections.IEnumerator implemented object, which can then be used to get items from the collection.

  • Use foreach (C#) or For Each (Visual Basic) to iterate through the collection.

The Count property specifies the total number of items in the collection, and is commonly used to determine the upper bound of the collection. You can add and remove items from the collection by using the Add and Remove methods.

The following code example demonstrates creating ListItemCollection objects, adding items to the collections, and removing items from the collections. In the example, the ListItemCollection named listBoxData is used as the data source for a ListBox control called ListBox1, and the ListItemCollection called ddBoxData is used as the data source for a DropDownList control called DropDownList1.

<%@ Page language="VB" 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 runat="server">
    Private Sub Page_Load(sender As Object, e As System.EventArgs) Handles MyBase.Load
        ' If this isn't the first time the page is loaded in this session,
        ' then don't recreate the DataTables.
        If Not IsPostBack Then
            ' Create a new ListItemCollection.
            Dim listBoxData As New ListItemCollection()
            ' Add items to the collection.
            listBoxData.Add(New ListItem("apples"))
            listBoxData.Add(New ListItem("bananas"))
            listBoxData.Add(New ListItem("cherries"))
            listBoxData.Add("grapes")
            listBoxData.Add("mangos")
            listBoxData.Add("oranges")
            ' Set the ListItemCollection as the data source for ListBox1.
            ListBox1.DataSource = listBoxData
            ListBox1.DataBind()

            ' Create a new ListItemCollection.
            Dim ddBoxData As New ListItemCollection()
            ' For now, just bind the data to the DropDownList.
            DropDownList1.DataSource = ddBoxData
            DropDownList1.DataBind()
        End If
    End Sub 'Page_Load

    Private Sub moveButton1_Click(sender As Object, e As System.EventArgs) 
        'Set the SelectedIndex to -1 so no items are selected.            
        ' The new item will be set as the selected item when it is added.
        DropDownList1.SelectedIndex = - 1
        ' Add the selected item to DropDownList1.
        DropDownList1.Items.Add(ListBox1.SelectedItem)
        ' Delete the selected item from ListBox1.
        ListBox1.Items.Remove(ListBox1.SelectedItem)
    End Sub 'moveButton1_Click


    Private Sub moveButton2_Click(sender As Object, e As System.EventArgs)
        'Set the SelectedIndex to -1 so no items are selected.
        ' The new item will be set as the selected item when it is added.
        ListBox1.SelectedIndex = - 1
        ' Add the selected item to ListBox1.
        ListBox1.Items.Add(DropDownList1.SelectedItem)
        'Delete the selected item from DropDownList1.
        DropDownList1.Items.Remove(DropDownList1.SelectedItem)
    End Sub 'moveButton2_Click
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
    <title>ASP.NET Example</title>
</head>

    <body>
        <form id="form1" runat="server">
            <table cellpadding="6" border="0">
                <tr>
                    <td rowspan="2" valign="top">
                        <asp:ListBox id="ListBox1" runat="server" 
                            SelectionMode="Single" Width="100px">
                        </asp:ListBox>
                    </td>

                    <td>
                        <asp:Button id="moveButton1" runat="server" Text="Move -->"
                            Width="100px" OnClick="moveButton1_Click"></asp:Button>
                    </td>

                    <td rowspan="2" valign="top">
                        <asp:DropDownList Runat="server" ID="DropDownList1"
                            Width="100px">
                        </asp:DropDownList>
                    </td>
                </tr>

                <tr>
                    <td>
                        <asp:Button ID="moveButton2" Runat="server" Text="<-- Move"
                            Width="100px" onClick="moveButton2_Click"></asp:Button>
                    </td>
                </tr>
            </table>
        </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 For Each loop 
to iterate through the ListItem objects in the ListItemCollection of ListBox1. -->
<%@ Page language="VB" 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 runat="server">
            ' Global Variables.
            Private dv As DataView
            Private dt As New DataTable()

            Private Sub Page_Load(sender As Object, e As System.EventArgs)
                ' 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") Is Nothing Then
                    ' 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()
                End If
            End Sub

            Private Sub addButton_Click(sender As Object, e As System.EventArgs)
                ' Add the items selected in ListBox1 to DataGrid1.
                Dim item As ListItem
                For Each item In ListBox1.Items
                    If item.Selected Then
                        ' Add the item to the DataGrid.
                        ' First, get the DataTable from the Session variable.
                        dt = CType(Session("data"), DataTable)

                        If  Not (dt Is Nothing) Then
                            ' Create a new DataRow in the DataTable.
                            Dim dr As 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()
                        End If
                    End If
                Next item
            End Sub
        </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

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 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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