DataListItemCollection Classe

Definição

Espaço de Nomes:: System.Web.UI.WebControls

Assemblagem:: System.Web.dll

Importante

Algumas informações dizem respeito a um produto pré-lançado que pode ser substancialmente modificado antes de ser lançado. A Microsoft não faz garantias, de forma expressa ou implícita, em relação à informação aqui apresentada.

Representa a coleção de DataListItem objetos no DataList controlo. Esta classe não pode ser herdada.

public ref class DataListItemCollection sealed : System::Collections::ICollection

public sealed class DataListItemCollection : System.Collections.ICollection

type DataListItemCollection = class
    interface ICollection
    interface IEnumerable

Public NotInheritable Class DataListItemCollection
Implements ICollection

Herança: Object
DataListItemCollection

Implementações: ICollection IEnumerable

Exemplos

O exemplo seguinte cria uma fonte de dados sob a forma de um DataView controlo e liga-o a um DataList controlo declarado em marcação. Depois, mostra o conteúdo do objeto subjacente DataListItemCollection na página.

<%@ 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;
}

// <Snippet2>
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;
}
// </Snippet2>

// <Snippet5>
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 + " ";
    }
}
// </Snippet5>

// <Snippet6>
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;
}
// </Snippet6>

</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>
                            
                        <%# 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>
                    <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="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

' <Snippet2>
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
    ' </Snippet2>

' <Snippet5>
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
' </Snippet5>

' <Snippet6>
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
    ' </Snippet6>

</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") %>' />
                            
                        <%# 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>
                    <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>

Observações

A DataListItemCollection classe representa uma coleção de DataListItem objetos, que por sua vez representam os itens de dados num DataList controlo. Para recuperar DataListItem objetos programaticamente de um DataList controlo, use um dos seguintes métodos:

Use o indexador para obter um único DataListItem objeto da coleção, usando notação de array.
Use o CopyTo método para copiar o conteúdo da coleção para um System.Array objeto, que pode depois ser usado para obter itens da coleção.
Use o GetEnumerator método para criar uma System.Collections.IEnumerator interface, que depois pode ser usada para obter itens da coleção.

A Count propriedade especifica o número total de itens na coleção e é frequentemente usada para determinar o limite superior da coleção.

Construtores

Name	Description
DataListItemCollection(ArrayList)	Inicializa uma nova instância da DataListItemCollection classe.

Propriedades

Name	Description
Count	Obtém o número de DataListItem objetos na coleção.
IsReadOnly	Obtém um valor que indica se os DataListItem objetos no DataListItemCollection podem ser modificados.
IsSynchronized	Recebe um valor que indica se o acesso ao DataListItemCollection é sincronizado (thread-safe).
Item[Int32]	Obtém um DataListItem objeto no índice especificado na coleção.
SyncRoot	Obtém o objeto que pode ser usado para sincronizar o acesso à DataListItemCollection coleção.

Métodos

Name	Description
CopyTo(Array, Int32)	Copia todos os itens desta DataListItemCollection coleção para o objeto especificado Array , começando no índice especificado no Array objeto.
Equals(Object)	Determina se o objeto especificado é igual ao objeto atual. (Herdado de Object)
GetEnumerator()	Devolve uma IEnumerator interface que contém todos os DataListItem objetos no DataListItemCollection.
GetHashCode()	Serve como função de hash predefinida. (Herdado de Object)
GetType()	Obtém o Type da instância atual. (Herdado de Object)
MemberwiseClone()	Cria uma cópia superficial do atual Object. (Herdado de Object)
ToString()	Devolve uma cadeia que representa o objeto atual. (Herdado de Object)

Métodos da Extensão

Name	Description
AsParallel(IEnumerable)	Permite a paralelização de uma consulta.
AsQueryable(IEnumerable)	Converte um IEnumerable para um IQueryable.
Cast<TResult>(IEnumerable)	Conjura os elementos de an IEnumerable para o tipo especificado.
OfType<TResult>(IEnumerable)	Filtra os elementos de um IEnumerable com base num tipo especificado.

Aplica-se a

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