OleDbDataAdapter.RowUpdating Evento

Definizione

Spazio dei nomi:

System.Data.OleDb

Assembly:

System.Data.OleDb.dll

Pacchetto:

System.Data.OleDb v8.0.0

Source:

OleDbDataAdapter.cs

Si verifica durante l'applicazione del metodo Update(DataSet) prima che un comando sia eseguito nell'origine dati. Viene eseguito un tentativo di aggiornamento. Di conseguenza, si verifica l'evento.

public:
 event System::Data::OleDb::OleDbRowUpdatingEventHandler ^ RowUpdating;

public event System.Data.OleDb.OleDbRowUpdatingEventHandler? RowUpdating;

member this.RowUpdating : System.Data.OleDb.OleDbRowUpdatingEventHandler 

Public Custom Event RowUpdating As OleDbRowUpdatingEventHandler 

Tipo evento

OleDbRowUpdatingEventHandler

Esempio

Nell'esempio seguente vengono illustrati gli RowUpdating eventi e RowUpdated usati.

public static void CreateDataAdapter(
    string connectionString)
{
    using (OleDbConnection connection = new OleDbConnection(connectionString))
    {
        OleDbDataAdapter adapter = new OleDbDataAdapter(
            "SELECT * FROM Customers WHERE CustomerID = 'ALFKI'", connection);

        adapter.InsertCommand = new OleDbCommand(
            "INSERT INTO Customers (CustomerID, CompanyName) VALUES(?, ?)",
            connection);

        adapter.InsertCommand.Parameters.Add(
            "@CustomerID", OleDbType.VarChar, 5, "CustomerID");
        adapter.InsertCommand.Parameters.Add(
            "@CompanyName", OleDbType.VarChar, 30, "CompanyName");

        connection.Open();

        DataSet custDS = new DataSet();
        adapter.Fill(custDS, "Customers");

        DataRow custRow = custDS.Tables["Customers"].NewRow();
        custRow["CustomerID"] = "NEWCO";
        custRow["CompanyName"] = "New Company";
        custDS.Tables["Customers"].Rows.Add(custRow);

        // add handlers
        adapter.RowUpdating += new OleDbRowUpdatingEventHandler(OnRowUpdating);
        adapter.RowUpdated += new OleDbRowUpdatedEventHandler(OnRowUpdated);

        adapter.Update(custDS, "Customers");

        // remove handlers
        adapter.RowUpdating -= new OleDbRowUpdatingEventHandler(OnRowUpdating);
        adapter.RowUpdated -= new OleDbRowUpdatedEventHandler(OnRowUpdated);

        foreach (DataRow row in custDS.Tables["Customers"].Rows)
        {
            if (row.HasErrors)
                Console.WriteLine(row.RowError);
        }
    }
}

protected static void OnRowUpdating(object sender,
    OleDbRowUpdatingEventArgs args)
{
    if (args.StatementType == StatementType.Insert)
    {
        System.IO.TextWriter writer = System.IO.File.AppendText("Inserts.log");
        writer.WriteLine("{0}: Customer {1} Inserted.",
            DateTime.Now, args.Row["CustomerID"]);
        writer.Close();
    }
}

protected static void OnRowUpdated(object sender, OleDbRowUpdatedEventArgs args)
{
    if (args.Status == UpdateStatus.ErrorsOccurred)
    {
        args.Row.RowError = args.Errors.Message;
        args.Status = UpdateStatus.SkipCurrentRow;
    }
}

Public Sub CreateDataAdapter(ByVal connectionString As String)
    Using connection As New OleDbConnection(connectionString)
        Dim adapter As New OleDbDataAdapter( _
            "SELECT * FROM Customers WHERE CustomerID = 'ALFKI'", connection)

        adapter.InsertCommand = New OleDbCommand( _
            "INSERT INTO Customers (CustomerID, CompanyName) VALUES(?, ?)", _
            connection)

        adapter.InsertCommand.Parameters.Add( _
            "@CustomerID", OleDbType.VarChar, 5, "CustomerID")
        adapter.InsertCommand.Parameters.Add( _
            "@CompanyName", OleDbType.VarChar, 30, "CompanyName")

        connection.Open()

        Dim custDS As New DataSet()
        adapter.Fill(custDS, "Customers")

        Dim custRow As DataRow = custDS.Tables("Customers").NewRow()
        custRow("CustomerID") = "NEWCO"
        custRow("CompanyName") = "New Company"
        custDS.Tables("Customers").Rows.Add(custRow)

        ' add handlers
        AddHandler adapter.RowUpdating, _
            New OleDbRowUpdatingEventHandler(AddressOf OnRowUpdating)
        AddHandler adapter.RowUpdated, _
            New OleDbRowUpdatedEventHandler(AddressOf OnRowUpdated)

        adapter.Update(custDS, "Customers")

        ' remove handlers
        RemoveHandler adapter.RowUpdating, _
            New OleDbRowUpdatingEventHandler(AddressOf OnRowUpdating)
        RemoveHandler adapter.RowUpdated, _
            New OleDbRowUpdatedEventHandler(AddressOf OnRowUpdated)

        Dim row As DataRow
        For Each row In custDS.Tables("Customers").Rows
            If row.HasErrors Then Console.WriteLine(row.RowError)
        Next
    End Using
End Sub

Sub OnRowUpdating(ByVal sender As Object, _
    ByVal args As OleDbRowUpdatingEventArgs)

    If args.StatementType = StatementType.Insert Then
        Dim writer As System.IO.TextWriter = _
            System.IO.File.AppendText("Inserts.log")
        writer.WriteLine("{0}: Customer {1} Inserted.", _
            DateTime.Now, args.Row("CustomerID"))
        writer.Close()
    End If
End Sub

Sub OnRowUpdated(ByVal sender As Object, _
    ByVal args As OleDbRowUpdatedEventArgs)

    If args.Status = UpdateStatus.ErrorsOccurred Then
        args.Row.RowError = args.Errors.Message
        args.Status = UpdateStatus.SkipCurrentRow
    End If
End Sub

Commenti

Quando si usa Update, sono presenti due eventi che si verificano per ogni riga di dati aggiornata. L'ordine di esecuzione è il seguente:

1. I valori nell'oggetto DataRow vengono spostati nei valori dei parametri.

2. Viene generato l'evento OnRowUpdating.

3. Il comando viene eseguito.

4. Se il comando è impostato su FirstReturnedRecord, il primo risultato restituito viene inserito in DataRow.

5. Se sono presenti parametri di output, vengono inseriti in DataRow.

6. Viene generato l'evento OnRowUpdated.

7. Chiamata del metodo AcceptChanges.

Vedi anche

• DataAdapter e DataReader