Export (0) Print
Expand All
This topic has not yet been rated - Rate this topic

DataListItemCollection Class

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

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

Namespace:  System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)
'Declaration
Public NotInheritable Class DataListItemCollection _
	Implements ICollection, IEnumerable

The DataListItemCollection type exposes the following members.

  NameDescription
Public methodDataListItemCollectionInitializes a new instance of the DataListItemCollection class.
Top
  NameDescription
Public propertyCountGets the number of DataListItem objects in the collection.
Public propertyIsReadOnlyGets a value that indicates whether the DataListItem objects in the DataListItemCollection can be modified.
Public propertyIsSynchronizedGets a value indicating whether access to the DataListItemCollection is synchronized (thread-safe).
Public propertyItemGets a DataListItem object at the specified index in the collection.
Public propertySyncRootGets the object that can be used to synchronize access to the DataListItemCollection collection.
Top
  NameDescription
Public methodCopyToCopies all the items from this DataListItemCollection collection to the specified System.Array object, starting at the specified index in the System.Array object.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodGetEnumeratorReturns a System.Collections.IEnumerator interface that contains all DataListItem objects in the DataListItemCollection.
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Top
  NameDescription
Public Extension MethodAsParallelEnables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension MethodAsQueryableConverts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension MethodCast(Of TResult)Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension MethodOfType(Of TResult)Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
Top

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.

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>

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Did you find this helpful?
(1500 characters remaining)
Thank you for your feedback
Show:
© 2014 Microsoft. All rights reserved.