DataListItemCollection Class (System.Web.UI.WebControls)

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.NET Framework Class Library

DataListItemCollection Class

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)

Syntax

Visual Basic (Declaration)

<AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class DataListItemCollection _
	Implements ICollection, IEnumerable

Visual Basic (Usage)

Dim instance As DataListItemCollection

[AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
public sealed class DataListItemCollection : ICollection, 
	IEnumerable

Visual C++

[AspNetHostingPermissionAttribute(SecurityAction::LinkDemand, Level = AspNetHostingPermissionLevel::Minimal)]
public ref class DataListItemCollection sealed : ICollection, 
	IEnumerable

JScript

public final class DataListItemCollection implements ICollection, IEnumerable

Remarks

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.

Visual Basic

<%@ 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>

<%@ Import Namespace = "System.Data"  %>
<%@ 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">
<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.

ICollection CreateDataSource()
{
    DataTable myDataTable = new DataTable();
    DataRow myDataRow;

    myDataTable.Columns.Add(new DataColumn("EmployeeName", typeof(string)));
    myDataTable.Columns.Add(new DataColumn("EmployeeID", typeof(long)));
    for (int i = 0; i < 3; i++)
    {
        myDataRow = myDataTable.NewRow();
        myDataRow[0] = "somename" + i.ToString();
        myDataRow[1] = (i+1000);
        myDataTable.Rows.Add(myDataRow);
    }
    DataView dataView = new DataView(myDataTable);
    return dataView;
}

void Page_Load(Object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        // Bind the DataView to the DataSource.
        myDataList.DataSource = CreateDataSource();
        myDataList.DataBind();
        // Create a Array to hold the DataSource.
        System.Array myArray = Array.CreateInstance(typeof(DataListItem),
            myDataList.Items.Count);
        // Copy the DataSource to an Array.
        myDataList.Items.CopyTo(myArray,0);
        PrintValues(myArray);
    }
}

// Prints each element in the Array onto the label lblAllItems1.
public void PrintValues(Array myArr)
{
    DataListItem currentItem;
    System.Collections.IEnumerator myEnumerator = myArr.GetEnumerator();
    while (myEnumerator.MoveNext())
    {
        currentItem = (DataListItem)myEnumerator.Current;
        lblAllItems1.Text += "<br /><br />" + 
            ((Label)(currentItem.Controls[1])).Text;
    }
}

// Event handler method for show button.
void show_Click(Object sender,EventArgs e)
{
    // Get the underlying DataListItemCollection from the DataList object.
    DataListItemCollection myDataListItemCollection = 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 = null;
}

void allItems_Click(Object sender,EventArgs e)
{
    IEnumerator dataListEnumerator;
    DataListItem currentItem;
    lblAllItems.Text = "";
    // Get an enumerator to traverse the DataListItemCollection.
    dataListEnumerator = myDataList.Items.GetEnumerator();
    while(dataListEnumerator.MoveNext())
    {
        currentItem = (DataListItem)dataListEnumerator.Current;
        // Display the current DataListItem onto the label.
        lblAllItems.Text += ((Label)(currentItem.Controls[1])).Text + " ";
    }
}

void itemSelected(Object sender,EventArgs e)
{
    // Get the underlying DataListItemCollection from the DataList object.
    DataListItemCollection myDataListItemCollection = myDataList.Items;
    // Get the index of the selected radio button in the RadioButtonList.
    int index = 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. 
    DataListItem currentItem = 
        ((DataListItemCollection)(myDataListItemCollection.SyncRoot))[index];
    // Display the selected DataListItem onto a label.
    lblDisplay.Text = "<b>DataListItem" + index + " is : "
        + ((Label)(currentItem.Controls[1])).Text;
    currentItem = null;
    myDataListItemCollection = null;
}

</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") %>'>
                        </asp:Label>
                        &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 Security

AspNetHostingPermission
for operating in a hosted environment. Demand value: LinkDemand; Permission value: Minimal.

Inheritance Hierarchy

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

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.

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

Reference

DataListItemCollection Members

System.Web.UI.WebControls Namespace

DataListItem

DataList

Items

CopyTo

GetEnumerator

Count

Other Resources

DataList Web Server Control Overview