DataSourceControl Classe

Definição

public ref class DataSourceControl abstract : System::Web::UI::Control, System::ComponentModel::IListSource, System::Web::UI::IDataSource

[System.ComponentModel.Bindable(false)]
public abstract class DataSourceControl : System.Web.UI.Control, System.ComponentModel.IListSource, System.Web.UI.IDataSource

[<System.ComponentModel.Bindable(false)>]
type DataSourceControl = class
    inherit Control
    interface IDataSource
    interface IListSource

Public MustInherit Class DataSourceControl
Inherits Control
Implements IDataSource, IListSource

Herança

Object

Control

DataSourceControl

Derivado

System.Web.UI.WebControls.EntityDataSource

System.Web.UI.WebControls.LinqDataSource

System.Web.UI.WebControls.ObjectDataSource

System.Web.UI.WebControls.QueryableDataSource

System.Web.UI.WebControls.SqlDataSource

Atributos

BindableAttribute

Implementações

IListSource IDataSource

Exemplos

O exemplo de código seguinte demonstra como uma classe pode estender a DataSourceControl classe. O CsvDataSource controlo representa os dados do ficheiro separados por vírgulas armazenados num ficheiro .csv. A CsvDataSource classe fornece as suas próprias implementações dos GetView, GetViewNames, e de outros métodos, porque as implementações da classe base não são funcionais.

using System;
using System.Collections;
using System.Data;
using System.IO;
using System.Security.Permissions;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

// The CsvDataSource is a data source control that retrieves its
// data from a comma-separated value file.
[AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
public class CsvDataSource : DataSourceControl
{
    public CsvDataSource() : base() {}

    // The comma-separated value file to retrieve data from.
    public string FileName {
        get {
            return ((CsvDataSourceView)this.GetView(String.Empty)).SourceFile;
        }
        set {
            // Only set if it is different.
            if ( ((CsvDataSourceView)this.GetView(String.Empty)).SourceFile != value) {
                ((CsvDataSourceView)this.GetView(String.Empty)).SourceFile = value;
                RaiseDataSourceChangedEvent(EventArgs.Empty);
            }
        }
    }

    // Do not add the column names as a data row. Infer columns if the CSV file does
    // not include column names.
    public bool IncludesColumnNames {
        get {
            return ((CsvDataSourceView)this.GetView(String.Empty)).IncludesColumnNames;
        }
        set {
            // Only set if it is different.
            if ( ((CsvDataSourceView)this.GetView(String.Empty)).IncludesColumnNames != value) {
                ((CsvDataSourceView)this.GetView(String.Empty)).IncludesColumnNames = value;
                RaiseDataSourceChangedEvent(EventArgs.Empty);
            }
        }
    }

    // Return a strongly typed view for the current data source control.
    private CsvDataSourceView view = null;
    protected override DataSourceView GetView(string viewName) {
        if (null == view) {
            view = new CsvDataSourceView(this, String.Empty);
        }
        return view;
    }
    // The ListSourceHelper class calls GetList, which
    // calls the DataSourceControl.GetViewNames method.
    // Override the original implementation to return
    // a collection of one element, the default view name.
    protected override ICollection GetViewNames() {
        ArrayList al = new ArrayList(1);
        al.Add(CsvDataSourceView.DefaultViewName);
        return al as ICollection;
    }
}

// The CsvDataSourceView class encapsulates the
// capabilities of the CsvDataSource data source control.
public class CsvDataSourceView : DataSourceView
{

    public CsvDataSourceView(IDataSource owner, string name) :base(owner, DefaultViewName) {
    }

    // The data source view is named. However, the CsvDataSource
    // only supports one view, so the name is ignored, and the
    // default name used instead.
    public static string DefaultViewName = "CommaSeparatedView";

    // The location of the .csv file.
    private string sourceFile = String.Empty;
    internal string SourceFile {
        get {
            return sourceFile;
        }
        set {
            // Use MapPath when the SourceFile is set, so that files local to the
            // current directory can be easily used.
            string mappedFileName = HttpContext.Current.Server.MapPath(value);
            sourceFile = mappedFileName;
        }
    }

    // Do not add the column names as a data row. Infer columns if the CSV file does
    // not include column names.
    private bool columns = false;
    internal bool IncludesColumnNames {
        get {
            return columns;
        }
        set {
            columns = value;
        }
    }

    // Get data from the underlying data source.
    // Build and return a DataView, regardless of mode.
    protected override IEnumerable ExecuteSelect(DataSourceSelectArguments selectArgs) {
        IEnumerable dataList = null;
        // Open the .csv file.
        if (File.Exists(this.SourceFile)) {
            DataTable data = new DataTable();

            // Open the file to read from.
            using (StreamReader sr = File.OpenText(this.SourceFile)) {
                // Parse the line
                string s = "";
                string[] dataValues;
                DataColumn col;

                // Do the following to add schema.
                dataValues = sr.ReadLine().Split(',');
                // For each token in the comma-delimited string, add a column
                // to the DataTable schema.
                foreach (string token in dataValues) {
                    col = new DataColumn(token,typeof(string));
                    data.Columns.Add(col);
                }

                // Do not add the first row as data if the CSV file includes column names.
                if (!IncludesColumnNames)
                    data.Rows.Add(CopyRowData(dataValues, data.NewRow()));

                // Do the following to add data.
                while ((s = sr.ReadLine()) != null) {
                    dataValues = s.Split(',');
                    data.Rows.Add(CopyRowData(dataValues, data.NewRow()));
                }
            }
            data.AcceptChanges();
            DataView dataView = new DataView(data);
            if (!string.IsNullOrEmpty(selectArgs.SortExpression)) {
                dataView.Sort = selectArgs.SortExpression;
            }
            dataList = dataView;
        }
        else {
            throw new System.Configuration.ConfigurationErrorsException("File not found, " + this.SourceFile);
        }

        if (null == dataList) {
            throw new InvalidOperationException("No data loaded from data source.");
        }

        return dataList;
    }

    private DataRow CopyRowData(string[] source, DataRow target) {
        try {
            for (int i = 0;i < source.Length;i++) {
                target[i] = source[i];
            }
        }
        catch (System.IndexOutOfRangeException) {
            // There are more columns in this row than
            // the original schema allows.  Stop copying
            // and return the DataRow.
            return target;
        }
        return target;
    }
    // The CsvDataSourceView does not currently
    // permit deletion. You can modify or extend
    // this sample to do so.
    public override bool CanDelete {
        get {
            return false;
        }
    }
    protected override int ExecuteDelete(IDictionary keys, IDictionary values)
    {
        throw new NotSupportedException();
    }
    // The CsvDataSourceView does not currently
    // permit insertion of a new record. You can
    // modify or extend this sample to do so.
    public override bool CanInsert {
        get {
            return false;
        }
    }
    protected override int ExecuteInsert(IDictionary values)
    {
        throw new NotSupportedException();
    }
    // The CsvDataSourceView does not currently
    // permit update operations. You can modify or
    // extend this sample to do so.
    public override bool CanUpdate {
        get {
            return false;
        }
    }
    protected override int ExecuteUpdate(IDictionary keys, IDictionary values, IDictionary oldValues)
    {
        throw new NotSupportedException();
    }
}

Imports System.Collections
Imports System.Data
Imports System.IO
Imports System.Security.Permissions
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls

Namespace Samples.AspNet.VB.Controls

' The CsvDataSource is a data source control that retrieves its
' data from a comma-separated value file.
<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public Class CsvDataSource
   Inherits DataSourceControl

   Public Sub New()
   End Sub

   ' The comma-separated value file to retrieve data from.
   Public Property FileName() As String
      Get
         Return CType(Me.GetView([String].Empty), CsvDataSourceView).SourceFile
      End Get
      Set
         ' Only set if it is different.
         If CType(Me.GetView([String].Empty), CsvDataSourceView).SourceFile <> value Then
            CType(Me.GetView([String].Empty), CsvDataSourceView).SourceFile = value
            RaiseDataSourceChangedEvent(EventArgs.Empty)
         End If
      End Set
   End Property

   ' Do not add the column names as a data row. Infer columns if the CSV file does
   ' not include column names.

   Public Property IncludesColumnNames() As Boolean
      Get
         Return CType(Me.GetView([String].Empty), CsvDataSourceView).IncludesColumnNames
      End Get
      Set
         ' Only set if it is different.
         If CType(Me.GetView([String].Empty), CsvDataSourceView).IncludesColumnNames <> value Then
            CType(Me.GetView([String].Empty), CsvDataSourceView).IncludesColumnNames = value
            RaiseDataSourceChangedEvent(EventArgs.Empty)
         End If
      End Set
   End Property


   ' Return a strongly typed view for the current data source control.
   Private view As CsvDataSourceView = Nothing

   Protected Overrides Function GetView(viewName As String) As DataSourceView
      If view Is Nothing Then
         view = New CsvDataSourceView(Me, String.Empty)
      End If
      Return view
   End Function 'GetView

   ' The ListSourceHelper class calls GetList, which
   ' calls the DataSourceControl.GetViewNames method.
   ' Override the original implementation to return
   ' a collection of one element, the default view name.
   Protected Overrides Function GetViewNames() As ICollection
      Dim al As New ArrayList(1)
      al.Add(CsvDataSourceView.DefaultViewName)
      Return CType(al, ICollection)
   End Function 'GetViewNames

End Class


' The CsvDataSourceView class encapsulates the
' capabilities of the CsvDataSource data source control.

Public Class CsvDataSourceView
   Inherits DataSourceView

   Public Sub New(owner As IDataSource, name As String)
       MyBase.New(owner, DefaultViewName)
   End Sub

   ' The data source view is named. However, the CsvDataSource
   ' only supports one view, so the name is ignored, and the
   ' default name used instead.
   Public Shared DefaultViewName As String = "CommaSeparatedView"

   ' The location of the .csv file.
   Private aSourceFile As String = [String].Empty

   Friend Property SourceFile() As String
      Get
         Return aSourceFile
      End Get
      Set
         ' Use MapPath when the SourceFile is set, so that files local to the
         ' current directory can be easily used.
         Dim mappedFileName As String
         mappedFileName = HttpContext.Current.Server.MapPath(value)
         aSourceFile = mappedFileName
      End Set
   End Property

   ' Do not add the column names as a data row. Infer columns if the CSV file does
   ' not include column names.
   Private columns As Boolean = False

   Friend Property IncludesColumnNames() As Boolean
      Get
         Return columns
      End Get
      Set
         columns = value
      End Set
   End Property

   ' Get data from the underlying data source.
   ' Build and return a DataView, regardless of mode.
   Protected Overrides Function ExecuteSelect(selectArgs As DataSourceSelectArguments) _
    As System.Collections.IEnumerable
      Dim dataList As IEnumerable = Nothing
      ' Open the .csv file.
      If File.Exists(Me.SourceFile) Then
         Dim data As New DataTable()

         ' Open the file to read from.
         Dim sr As StreamReader = File.OpenText(Me.SourceFile)

         Try
            ' Parse the line
            Dim dataValues() As String
            Dim col As DataColumn

            ' Do the following to add schema.
            dataValues = sr.ReadLine().Split(","c)
            ' For each token in the comma-delimited string, add a column
            ' to the DataTable schema.
            Dim token As String
            For Each token In dataValues
               col = New DataColumn(token, System.Type.GetType("System.String"))
               data.Columns.Add(col)
            Next token

            ' Do not add the first row as data if the CSV file includes column names.
            If Not IncludesColumnNames Then
               data.Rows.Add(CopyRowData(dataValues, data.NewRow()))
            End If

            ' Do the following to add data.
            Dim s As String
            Do
               s = sr.ReadLine()
               If Not s Is Nothing Then
                   dataValues = s.Split(","c)
                   data.Rows.Add(CopyRowData(dataValues, data.NewRow()))
               End If
            Loop Until s Is Nothing

         Finally
            sr.Close()
         End Try

         data.AcceptChanges()
         Dim dataView As New DataView(data)
         If Not selectArgs.SortExpression Is String.Empty Then
             dataView.Sort = selectArgs.SortExpression
         End If
         dataList = dataView
      Else
         Throw New System.Configuration.ConfigurationErrorsException("File not found, " + Me.SourceFile)
      End If

      If dataList is Nothing Then
         Throw New InvalidOperationException("No data loaded from data source.")
      End If

      Return dataList
   End Function 'ExecuteSelect


   Private Function CopyRowData([source]() As String, target As DataRow) As DataRow
      Try
         Dim i As Integer
         For i = 0 To [source].Length - 1
            target(i) = [source](i)
         Next i
      Catch iore As IndexOutOfRangeException
         ' There are more columns in this row than
         ' the original schema allows.  Stop copying
         ' and return the DataRow.
         Return target
      End Try
      Return target
   End Function 'CopyRowData

   ' The CsvDataSourceView does not currently
   ' permit deletion. You can modify or extend
   ' this sample to do so.
   Public Overrides ReadOnly Property CanDelete() As Boolean
      Get
         Return False
      End Get
   End Property

   Protected Overrides Function ExecuteDelete(keys As IDictionary, values As IDictionary) As Integer
      Throw New NotSupportedException()
   End Function 'ExecuteDelete

   ' The CsvDataSourceView does not currently
   ' permit insertion of a new record. You can
   ' modify or extend this sample to do so.
   Public Overrides ReadOnly Property CanInsert() As Boolean
      Get
         Return False
      End Get
   End Property

   Protected Overrides Function ExecuteInsert(values As IDictionary) As Integer
      Throw New NotSupportedException()
   End Function 'ExecuteInsert

   ' The CsvDataSourceView does not currently
   ' permit update operations. You can modify or
   ' extend this sample to do so.
   Public Overrides ReadOnly Property CanUpdate() As Boolean
      Get
         Return False
      End Get
   End Property

   Protected Overrides Function ExecuteUpdate(keys As IDictionary, _
                                              values As IDictionary, _
                                              oldValues As IDictionary) As Integer
      Throw New NotSupportedException()
   End Function 'ExecuteUpdate

End Class
End Namespace

O exemplo de código seguinte demonstra como usar o CsvDataSource controlo num formulário Web.

<%@ Page Language="C#" %>
<%@ Register Tagprefix="aspSample"
             Namespace="Samples.AspNet.CS.Controls" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">

      <asp:gridview
          id="GridView1"
          runat="server"
          allowsorting="True"
          datasourceid="CsvDataSource1" />

      <aspSample:CsvDataSource
          id = "CsvDataSource1"
          runat = "server"
          filename = "sample.csv"
          includescolumnnames="True" />

    </form>
  </body>
</html>

<%@ Page Language="VB" %>
<%@ Register Tagprefix="aspSample"
             Namespace="Samples.AspNet.VB.Controls" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
        <form id="form1" runat="server">

            <asp:gridview
                id="GridView1"
                runat="server"
                allowsorting="True"
                datasourceid="CsvDataSource1" />

            <aspSample:CsvDataSource
                id = "CsvDataSource1"
                runat = "server"
                filename = "sample.csv"
                includescolumnnames="True" />

        </form>
    </body>
</html>

Observações

O ASP.NET suporta uma arquitetura de ligação de dados de controlo que permite que os controlos do servidor Web se associem aos dados de forma consistente. Os controlos de servidor web que se ligam a dados são chamados controlos de ligação de dados, e as classes que facilitam essa ligação são chamadas controlos de fonte de dados. Os controlos de fonte de dados podem representar qualquer fonte de dados: uma base de dados relacional, um ficheiro, um fluxo, um objeto de negócio, e assim por diante. Os controlos de fonte de dados apresentam dados de forma consistente aos controlos ligados aos dados, independentemente da origem ou formato dos dados subjacentes.

Utiliza-se os controlos de fonte de dados fornecidos com ASP.NET, incluindo SqlDataSource, AccessDataSource e XmlDataSource, para realizar a maioria das tarefas de desenvolvimento Web. Usas a classe base DataSourceControl quando quiseres implementar o teu próprio controlo de fonte de dados personalizado.

Embora qualquer classe que implemente a interface IDataSource seja um controlo de fonte de dados, a maioria ASP.NET controlos de fonte de dados estende a classe abstrata DataSourceControl, que fornece uma implementação base da interface IDataSource. A DataSourceControl classe também fornece uma implementação da IListSource interface, que permite atribuir programaticamente o controlo de fonte de dados à DataSource propriedade de um controlo ligado a dados e devolver dados ao controlo como uma lista básica.

Qualquer controlo de ASP.NET que derive da classe DataBoundControl pode ser ligado a um controlo de fonte de dados. Quando a DataBoundControl está associado a um controlo de fonte de dados, a ligação de dados é realizada automaticamente em tempo de execução. Também pode usar controlos de fonte de dados com controlos ASP.NET que expõem uma propriedade DataSource ou DataSourceID e suportam ligação básica de dados, mas não derivam de DataBoundControl. Ao usar estes controlos data-bound, deve chamar explicitamente o DataBind método. Para mais informações sobre ligação de dados, consulte ASP.NET Data Access Content Map.

Pode pensar num controlo de fonte de dados como a combinação do DataSourceControl objeto e das suas listas associadas de dados, chamadas vistas de fonte de dados. Cada lista de dados é representada por um DataSourceView objeto. Como o armazenamento de dados subjacente contém uma ou mais listas de dados, a DataSourceControl está sempre associado a um ou mais objetos nomeados DataSourceView . A IDataSource interface define os métodos que todos os controlos de fonte de dados usam para interagir com as vistas de fonte de dados: o GetViewNames método é usado para enumerar as vistas de fonte de dados atualmente associadas ao controlo de fonte de dados, e o GetView método é usado para recuperar uma instância específica de vista de fonte de dados pelo nome.

Também pode pensar no controlo de fontes de dados como duas interfaces distintas que os chamadores usam para aceder aos dados. A DataSourceControl classe é a interface com que os programadores de páginas interagem diretamente ao desenvolver uma página Web Forms, e a DataSourceView classe é a interface com a qual os controlos encadernados por dados e os autores de controlos encadernados interagem. Como o DataSourceView objeto está disponível apenas em tempo de execução, qualquer estado persistido para o controlo de fonte de dados ou para a vista da fonte de dados deve ser exposto diretamente pelo controlo de fonte de dados.

Não existe renderização visual dos controlos de fonte de dados ASP.NET; são implementados como controlos para que possa criá-los declarativamente e, opcionalmente, permitir que participem na gestão de estados. Como resultado, os controlos de fonte de dados não suportam funcionalidades visuais como EnableTheming ou SkinID.

Ver também

• IDataSource
• DataSourceView
• DataBoundControl
• HierarchicalDataSourceControl