DataSourceView DataSourceView DataSourceView DataSourceView Class

Definizione

Funge da classe base per tutte le classi di visualizzazione origine dati, che definiscono le funzionalità dei controlli origine dati.Serves as the base class for all data source view classes, which define the capabilities of data source controls.

public ref class DataSourceView abstract
public abstract class DataSourceView
type DataSourceView = class
Public MustInherit Class DataSourceView
Ereditarietà
DataSourceViewDataSourceViewDataSourceViewDataSourceView
Derivato

Esempi

Nell'esempio di codice riportato di seguito viene illustrato DataSourceView come estendere la classe per creare una classe di visualizzazione fortemente tipizzata per un controllo origine dati.The following code example demonstrates how to extend the DataSourceView class to create a strongly typed view class for a data source control. La CsVDataSourceView classe definisce le funzionalità CsvDataSource del controllo origine dati e fornisce un'implementazione per i controlli associati a dati per l'utilizzo di dati archiviati in file con valori delimitati da virgole (CSV).The CsVDataSourceView class defines the capabilities of the CsvDataSource data source control and provides an implementation for data-bound controls to use data stored in comma-separated value (.csv) files. Per ulteriori informazioni sul CsvDataSource controllo origine dati, vedere la DataSourceControl classe.For more information on the CsvDataSource data source control, see the DataSourceControl class.

// 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();
    }
}
' 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

Commenti

ASP.NET supporta un'architettura di associazione dati che consente ai controlli server Web di associare i dati in modo coerente.ASP.NET supports a data-binding architecture that enables Web server controls to bind to data in a consistent fashion. I controlli server Web che si associano ai dati vengono definiti controlli con associazione a dati e le classi che facilitano tale associazione sono denominate controlli origine dati.Web server controls that bind to data are referred to as data-bound controls, and the classes that facilitate that binding are called data source controls. I controlli origine dati possono rappresentare qualsiasi origine dati, ovvero un database relazionale, un file, un flusso, un oggetto business e così via.Data source controls can represent any data source: a relational database, a file, a stream, a business object, and so on. I controlli origine dati presentano i dati in modo coerente ai controlli con associazione a dati, indipendentemente dall'origine o dal formato dei dati sottostanti.Data source controls present data in a consistent way to data-bound controls, regardless of the source or format of the underlying data.

Per eseguire la maggior parte delle attività di sviluppo Web, è possibile SqlDataSourceutilizzare AccessDataSourcei controlli XmlDataSourceorigine dati forniti con ASP.NET, inclusi, e.You use the data source controls that are provided with ASP.NET, including SqlDataSource, AccessDataSource, and XmlDataSource, to perform most Web development tasks. Si utilizzano le classi DataSourceControl di DataSourceView base e quando si desidera implementare il proprio controllo origine dati personalizzato.You use the base DataSourceControl and DataSourceView classes when you want to implement your own custom data source control.

È possibile considerare un controllo origine dati come la combinazione dell' IDataSource oggetto e degli elenchi di dati associati, detti viste origine dati.You can think of a data source control as the combination of the IDataSource object and its associated lists of data, called data source views. Ogni elenco di dati è rappresentato da un DataSourceView oggetto.Each list of data is represented by a DataSourceView object. La DataSourceView classe è la classe base per tutte le viste origine dati oppure gli elenchi di dati associati ai controlli origine dati.The DataSourceView class is the base class for all data source views, or lists of data, associated with data source controls. Le viste origine dati definiscono le funzionalità di un controllo origine dati.Data source views define the capabilities of a data source control. Poiché l'archivio dati sottostante contiene uno o più elenchi di dati, un controllo origine dati è sempre associato a una o più viste origine dati denominate.Because the underlying data storage contains one or more lists of data, a data source control is always associated with one or more named data source views. Il controllo origine dati utilizza il GetViewNames metodo per enumerare le viste origine dati attualmente associate al controllo origine dati e il GetView metodo per recuperare un'istanza della vista origine dati specifica in base al nome.The data source control uses the GetViewNames method to enumerate the data source views currently associated with the data source control and the GetView method to retrieve a specific data source view instance by name.

Tutti DataSourceView gli oggetti supportano il recupero dei dati dall'origine dati sottostante usando ExecuteSelect il metodo.All DataSourceView objects support data retrieval from the underlying data source using the ExecuteSelect method. Tutte le visualizzazioni supportano facoltativamente un set di operazioni di base, tra cui ExecuteInsertoperazioni ExecuteUpdatequali, ExecuteDeletee.All views optionally support a basic set of operations, including operations such as ExecuteInsert, ExecuteUpdate, and ExecuteDelete. Un controllo con associazione a dati consente di individuare le funzionalità di un controllo origine dati recuperando una vista origine dati associata utilizzando GetView i GetViewNames metodi e e eseguendo una query sulla vista in fase di progettazione o di esecuzione.A data-bound control can discover the capabilities of a data source control by retrieving an associated data source view using the GetView and GetViewNames methods, and by querying the view at design time or run time.

Costruttori

DataSourceView(IDataSource, String) DataSourceView(IDataSource, String) DataSourceView(IDataSource, String) DataSourceView(IDataSource, String)

Inizializza una nuova istanza della classe DataSourceView.Initializes a new instance of the DataSourceView class.

Proprietà

CanDelete CanDelete CanDelete CanDelete

Ottiene un valore che indica se l'oggetto DataSourceView associato all'oggetto DataSourceControl corrente supporta l'operazione ExecuteDelete(IDictionary, IDictionary).Gets a value indicating whether the DataSourceView object associated with the current DataSourceControl object supports the ExecuteDelete(IDictionary, IDictionary) operation.

CanInsert CanInsert CanInsert CanInsert

Ottiene un valore che indica se l'oggetto DataSourceView associato all'oggetto DataSourceControl corrente supporta l'operazione ExecuteInsert(IDictionary).Gets a value indicating whether the DataSourceView object associated with the current DataSourceControl object supports the ExecuteInsert(IDictionary) operation.

CanPage CanPage CanPage CanPage

Ottiene un valore che indica se l'oggetto DataSourceView associato all'oggetto DataSourceControl corrente supporta lo spostamento dei dati recuperati tramite il metodo ExecuteSelect(DataSourceSelectArguments).Gets a value indicating whether the DataSourceView object associated with the current DataSourceControl object supports paging through the data retrieved by the ExecuteSelect(DataSourceSelectArguments) method.

CanRetrieveTotalRowCount CanRetrieveTotalRowCount CanRetrieveTotalRowCount CanRetrieveTotalRowCount

Ottiene un valore che indica se l'oggetto DataSourceView associato all'oggetto DataSourceControl corrente supporta il recupero del numero totale di righe di dati anziché dei dati.Gets a value indicating whether the DataSourceView object associated with the current DataSourceControl object supports retrieving the total number of data rows, instead of the data.

CanSort CanSort CanSort CanSort

Ottiene un valore che indica se l'oggetto DataSourceView associato all'oggetto DataSourceControl corrente supporta una visualizzazione ordinata dell'origine dati sottostante.Gets a value indicating whether the DataSourceView object associated with the current DataSourceControl object supports a sorted view on the underlying data source.

CanUpdate CanUpdate CanUpdate CanUpdate

Ottiene un valore che indica se l'oggetto DataSourceView associato all'oggetto DataSourceControl corrente supporta l'operazione ExecuteUpdate(IDictionary, IDictionary, IDictionary).Gets a value indicating whether the DataSourceView object associated with the current DataSourceControl object supports the ExecuteUpdate(IDictionary, IDictionary, IDictionary) operation.

Events Events Events Events

Ottiene un elenco di delegati del gestore eventi per la visualizzazione origine dati.Gets a list of event-handler delegates for the data source view.

Name Name Name Name

Ottiene il nome della visualizzazione origine dati.Gets the name of the data source view.

Metodi

CanExecute(String) CanExecute(String) CanExecute(String) CanExecute(String)

Determina se è possibile eseguire il comando specificato.Determines whether the specified command can be executed.

Delete(IDictionary, IDictionary, DataSourceViewOperationCallback) Delete(IDictionary, IDictionary, DataSourceViewOperationCallback) Delete(IDictionary, IDictionary, DataSourceViewOperationCallback) Delete(IDictionary, IDictionary, DataSourceViewOperationCallback)

Esegue un'operazione di eliminazione asincrona sull'elenco di dati rappresentato dall'oggetto DataSourceView.Performs an asynchronous delete operation on the list of data that the DataSourceView object represents.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determina se l'oggetto specificato è uguale all'oggetto corrente.Determines whether the specified object is equal to the current object.

(Inherited from Object)
ExecuteCommand(String, IDictionary, IDictionary) ExecuteCommand(String, IDictionary, IDictionary) ExecuteCommand(String, IDictionary, IDictionary) ExecuteCommand(String, IDictionary, IDictionary)

Esegue il comando specificato.Executes the specified command.

ExecuteCommand(String, IDictionary, IDictionary, DataSourceViewOperationCallback) ExecuteCommand(String, IDictionary, IDictionary, DataSourceViewOperationCallback) ExecuteCommand(String, IDictionary, IDictionary, DataSourceViewOperationCallback) ExecuteCommand(String, IDictionary, IDictionary, DataSourceViewOperationCallback)

Esegue il comando specificato.Executes the specified command.

ExecuteDelete(IDictionary, IDictionary) ExecuteDelete(IDictionary, IDictionary) ExecuteDelete(IDictionary, IDictionary) ExecuteDelete(IDictionary, IDictionary)

Esegue un'operazione di eliminazione sull'elenco di dati rappresentato dall'oggetto DataSourceView.Performs a delete operation on the list of data that the DataSourceView object represents.

ExecuteInsert(IDictionary) ExecuteInsert(IDictionary) ExecuteInsert(IDictionary) ExecuteInsert(IDictionary)

Esegue un'operazione di inserimento sull'elenco di dati rappresentato dall'oggetto DataSourceView.Performs an insert operation on the list of data that the DataSourceView object represents.

ExecuteSelect(DataSourceSelectArguments) ExecuteSelect(DataSourceSelectArguments) ExecuteSelect(DataSourceSelectArguments) ExecuteSelect(DataSourceSelectArguments)

Ottiene un elenco di dati dall'archivio dati sottostante.Gets a list of data from the underlying data storage.

ExecuteUpdate(IDictionary, IDictionary, IDictionary) ExecuteUpdate(IDictionary, IDictionary, IDictionary) ExecuteUpdate(IDictionary, IDictionary, IDictionary) ExecuteUpdate(IDictionary, IDictionary, IDictionary)

Esegue un'operazione di aggiornamento sull'elenco di dati rappresentato dall'oggetto DataSourceView.Performs an update operation on the list of data that the DataSourceView object represents.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Funge da funzione hash predefinita.Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Ottiene l'oggetto Type dell'istanza corrente.Gets the Type of the current instance.

(Inherited from Object)
Insert(IDictionary, DataSourceViewOperationCallback) Insert(IDictionary, DataSourceViewOperationCallback) Insert(IDictionary, DataSourceViewOperationCallback) Insert(IDictionary, DataSourceViewOperationCallback)

Esegue un'operazione di inserimento asincrona sull'elenco di dati rappresentato dall'oggetto DataSourceView.Performs an asynchronous insert operation on the list of data that the DataSourceView object represents.

MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Crea una copia superficiale dell'oggetto Object corrente.Creates a shallow copy of the current Object.

(Inherited from Object)
OnDataSourceViewChanged(EventArgs) OnDataSourceViewChanged(EventArgs) OnDataSourceViewChanged(EventArgs) OnDataSourceViewChanged(EventArgs)

Genera l'evento DataSourceViewChanged.Raises the DataSourceViewChanged event.

RaiseUnsupportedCapabilityError(DataSourceCapabilities) RaiseUnsupportedCapabilityError(DataSourceCapabilities) RaiseUnsupportedCapabilityError(DataSourceCapabilities) RaiseUnsupportedCapabilityError(DataSourceCapabilities)

Viene chiamato dal metodo RaiseUnsupportedCapabilitiesError(DataSourceView) per confrontare le funzionalità richieste per un'operazione ExecuteSelect(DataSourceSelectArguments) con quelle supportate dalla visualizzazione.Called by the RaiseUnsupportedCapabilitiesError(DataSourceView) method to compare the capabilities requested for an ExecuteSelect(DataSourceSelectArguments) operation against those that the view supports.

Select(DataSourceSelectArguments, DataSourceViewSelectCallback) Select(DataSourceSelectArguments, DataSourceViewSelectCallback) Select(DataSourceSelectArguments, DataSourceViewSelectCallback) Select(DataSourceSelectArguments, DataSourceViewSelectCallback)

Ottiene un elenco di dati dall'archivio dati sottostante in modo asincrono.Gets a list of data asynchronously from the underlying data storage.

ToString() ToString() ToString() ToString()

Restituisce una stringa che rappresenta l'oggetto corrente.Returns a string that represents the current object.

(Inherited from Object)
Update(IDictionary, IDictionary, IDictionary, DataSourceViewOperationCallback) Update(IDictionary, IDictionary, IDictionary, DataSourceViewOperationCallback) Update(IDictionary, IDictionary, IDictionary, DataSourceViewOperationCallback) Update(IDictionary, IDictionary, IDictionary, DataSourceViewOperationCallback)

Esegue un'operazione di aggiornamento asincrona sull'elenco di dati rappresentato dall'oggetto DataSourceView.Performs an asynchronous update operation on the list of data that the DataSourceView object represents.

Eventi

DataSourceViewChanged DataSourceViewChanged DataSourceViewChanged DataSourceViewChanged

Si verifica quando la visualizzazione origine dati ha subito una modifica.Occurs when the data source view has changed.

Si applica a

Vedi anche