DataListItemCollection Class

.NET Framework (current version)

Other Versions

Represents the collection of DataListItem objects in the DataList control. This class cannot be inherited.

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

Inheritance Hierarchy

System.Object
System.Web.UI.WebControls.DataListItemCollection

Syntax

C++

Public NotInheritable Class DataListItemCollection
	Implements ICollection, IEnumerable

Constructors

	Name	Description
	DataListItemCollection(ArrayList)	Initializes a new instance of the DataListItemCollection class.

Properties

	Name	Description
	Count	Gets the number of DataListItem objects in the collection.
	IsReadOnly	Gets a value that indicates whether the DataListItem objects in the DataListItemCollection can be modified.
	IsSynchronized	Gets a value indicating whether access to the DataListItemCollection is synchronized (thread-safe).
	Item(Int32)	Gets a DataListItem object at the specified index in the collection.
	SyncRoot	Gets the object that can be used to synchronize access to the DataListItemCollection collection.

Methods

	Name	Description
	CopyTo(Array, Int32)	Copies all the items from this DataListItemCollection collection to the specified System.Array object, starting at the specified index in the System.Array object.
	Equals(Object)	Determines whether the specified object is equal to the current object.(Inherited from Object.)
	GetEnumerator()	Returns a System.Collections.IEnumerator interface that contains all DataListItem objects in the DataListItemCollection.
	GetHashCode()	Serves as the default hash function. (Inherited from Object.)
	GetType()	Gets the Type of the current instance.(Inherited from Object.)
	ToString()	Returns a string that represents the current object.(Inherited from Object.)

Extension Methods

	Name	Description
	AsParallel()	Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)
	AsQueryable()	Overloaded. Converts an IEnumerable to an IQueryable.(Defined by Queryable.)
	Cast(Of TResult)()	Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)
	OfType(Of TResult)()	Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

The DataListItemCollection class represents a collection of DataListItem objects, which in turn represent the data items in a DataList control. To programmatically retrieve DataListItem objects from a DataList control, use one of the following methods:

Use the indexer to get a single DataListItem object 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 interface, which can then be used to get items from 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.

Examples

The following example creates a data source in the form of a DataView control and binds it to a DataList control declared in markup. It then displays the contents of the underlying DataListItemCollection object on the page.

<%@ Import Namespace = "System.Data"  %>
<%@ Page language="VB" AutoEventWireup="true"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">    
' The following example creates a DataSource as a DataView.
' The DataView is bound to a DataList that is displayed using an
' ItemTemplate. When the page is first loaded, the program uses the 
' CopyTo method to copy the entire data source to an Array and then 
' displays that data.

Function CreateDataSource() As ICollection 
    Dim myDataTable As DataTable = New DataTable()
    Dim myDataRow As DataRow 
    Dim i As Integer

    myDataTable.Columns.Add(New DataColumn("EmployeeName", GetType(String)))
    myDataTable.Columns.Add(New DataColumn("EmployeeID", GetType(Integer)))
    For i = 0 To 2
        myDataRow = myDataTable.NewRow()
        myDataRow(0) = "somename" + i.ToString()
        myDataRow(1) = i + 1000
        myDataTable.Rows.Add(myDataRow)
    Next 
    CreateDataSource = new DataView(myDataTable)
End Function

Sub Page_Load(sender As object, e As EventArgs)
    If (Not IsPostBack)
        ' Bind the DataView to the DataSource.
        myDataList.DataSource = CreateDataSource()
        myDataList.DataBind()
        ' Create a Array to hold the DataSource.
        Dim myArray As System.Array = Array.CreateInstance(GetType(DataListItem), _
            myDataList.Items.Count)
        ' Copy the DataSource to an Array.
        myDataList.Items.CopyTo(myArray, 0)
        PrintValues(myArray)
    End If
End sub

' Prints each element in the Array onto the label lblAllItems1.
Public Sub PrintValues(myArr As Array)
    Dim currentItem As DataListItem 
    Dim myEnumerator As System.Collections.IEnumerator = myArr.GetEnumerator()
    While (myEnumerator.MoveNext())
        currentItem = CType(myEnumerator.Current,DataListItem)
        lblAllItems1.Text = lblAllItems1.Text & "<br /><br />" & _
            CType(currentItem.Controls(1),Label).Text
    End While
End Sub

    ' Event handler method for show button.
Sub show_Click(sender as Object, e As EventArgs)
    ' Get the underlying DataListItemCollection from the DataList object.
    Dim myDataListItemCollection As DataListItemCollection = myDataList.Items
    ' Display the read-only properties.
    Response.Write("<b>The Total number of items are " & _
        myDataListItemCollection.Count & "</b>")
        Response.Write("<br /><b>The ReadOnly property of the " & _
            "DataListItemCollection is always " & _
            myDataListItemCollection.IsReadOnly & "</b>")
        Response.Write("<br /><b>The IsSynchronized property of the " & _
            "DataListItemCollection is always " _
            & myDataListItemCollection.IsSynchronized & "</b>")
    myDataListItemCollection = Nothing
End Sub

Sub AllItems_Click(sender As Object, e As EventArgs)
    Dim dataListEnumerator As IEnumerator
    Dim currentItem As DataListItem 
    lblAllItems.Text = ""
    ' Get an enumerator to traverse the DataListItemCollection.
    dataListEnumerator = myDataList.Items.GetEnumerator()
    while(dataListEnumerator.MoveNext())
        currentItem = CType(dataListEnumerator.Current,DataListItem)
        ' Display the current DataListItem onto the label.
        lblAllItems.Text = lblAllItems.Text & CType((currentItem.Controls(1)), _
        Label).Text & "  "
    End While
End Sub

Sub ItemSelected(sender As object, e As EventArgs)
    ' Get the underlying DataListItemCollection from the DataList object.
    Dim myDataListItemCollection As DataListItemCollection  = myDataList.Items
    ' Get the index of the selected radio button in the RadioButtonList.
    Dim index As Integer = Convert.ToInt16(listItemNo.SelectedItem.Value)
    ' Get the DataListItem corresponding to index from DataList.
    ' SyncRoot is used to make access to the DataListItemCollection 
    ' in a thread-safe manner It returns the object that invoked it. 
    Dim currentItem As DataListItem = _ 
        CType(myDataListItemCollection.SyncRoot,DataListItemCollection)(index)
    ' Display the selected DataListItem onto a label.
    lblDisplay.Text = "<b>DataListItem" & index & " is: " _
        & CType(currentItem.Controls(1),Label).Text
    currentItem = Nothing
    myDataListItemCollection = Nothing
End Sub

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>
        DataListItemCollection Example
    </title>
</head>
<body>
<form runat="server" id="Form1">
    <h3>
        DataListItemCollection Example
    </h3>
    <table>
        <tr>
            <td>
                <asp:datalist id="myDataList" runat="server" Font-Size="8pt" 
                    Font-Names="Verdana" BorderColor="black" CellSpacing="5"
                    CellPadding="10" GridLines="Horizontal">
                    <HeaderStyle BackColor="#aaaadd"></HeaderStyle>
                    <HeaderTemplate>
                        EmployeeName EmployeeID
                    </HeaderTemplate>
                    <ItemTemplate>
                        <asp:Label id="label1"  runat="server"
                            Text='<%# DataBinder.Eval(Container.DataItem, "EmployeeName") %>' />
                        &nbsp;&nbsp;&nbsp;&nbsp;
                        <%# DataBinder.Eval(Container.DataItem, "EmployeeID")%>
                    </ItemTemplate>
                </asp:datalist>
            </td>
            <td>
                <asp:label id="lblAllItems1" 
                    Text="The following items <br /> are copied to the array: " 
                    Runat="server" ForeColor="blue" Font-Bold="true" 
                    AssociatedControlID="listItemNo">
                    The following items <br /> are copied to the array:
                </asp:label>
            </td>
            <td>
                &nbsp;&nbsp;&nbsp; <b>Show Items:</b>
                <asp:RadioButtonList ID="listItemNo" 
                    OnSelectedIndexChanged="itemSelected" AutoPostBack="true" 
                    Runat="server">
                    <asp:ListItem Value="0" Text="0"></asp:ListItem>
                    <asp:ListItem Value="1" Text="1"></asp:ListItem>
                    <asp:ListItem Value="2" Text="2"></asp:ListItem>
                </asp:RadioButtonList>
            </td>
            <td>
                <asp:Label ID="lblDisplay" Runat="server" />
            </td>
        </tr>
    </table>
    <p>
        <asp:button id="show" onclick="show_Click" Runat="server" 
            Font-Bold="True" Text="DataList Information" />
        <asp:button id="allitems" onclick="allItems_Click" Runat="server" 
            Font-Bold="True" Text="Show All DataListItems" />
    </p>
    <p>
        <b>All DataList items will be shown here:</b>
        <asp:label id="lblAllItems" Runat="server" ForeColor="blue" />
    </p>
</form>
</body>
</html>

Version Information

.NET Framework
Available since 1.1

Thread Safety

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