ObjectDataSource.Updating ObjectDataSource.Updating ObjectDataSource.Updating ObjectDataSource.Updating Event

Definizione

Si verifica prima di un'operazione Update().Occurs before an Update() operation.

public:
 event System::Web::UI::WebControls::ObjectDataSourceMethodEventHandler ^ Updating;
public event System.Web.UI.WebControls.ObjectDataSourceMethodEventHandler Updating;
member this.Updating : System.Web.UI.WebControls.ObjectDataSourceMethodEventHandler 
Public Custom Event Updating As ObjectDataSourceMethodEventHandler 

Esempi

Nei tre esempi seguenti vengono illustrate una pagina Web, una classe di pagine code-behind e una classe di accesso ai dati che consentono a un utente di recuperare e aggiornare i record nella tabella Employees del database Northwind.The following three examples show a Web page, a code-behind page class, and a data-access class that enable a user to retrieve and update records in the Employees table in the Northwind database.

Nel primo esempio viene illustrata una pagina Web contenente ObjectDataSource due controlli, DropDownList un controllo e un DetailsView controllo.The first example shows a Web page that contains two ObjectDataSource controls, a DropDownList control, and a DetailsView control. Il primo ObjectDataSource controllo e il DropDownList controllo vengono utilizzati per recuperare e visualizzare i nomi dei dipendenti dal database.The first ObjectDataSource control and the DropDownList control are used to retrieve and display employee names from the database. Il secondo ObjectDataSource controllo e il DetailsView controllo vengono utilizzati per recuperare, visualizzare e modificare i dati dal record del dipendente selezionato dall'utente.The second ObjectDataSource control and the DetailsView control are used to retrieve, display, and modify the data from the employee record that is selected by the user.

<form id="Form1" method="post" runat="server">

    <asp:objectdatasource
      ID="ObjectDataSource1"
      runat="server"
      SelectMethod="GetFullNamesAndIDs"
      TypeName="Samples.AspNet.CS.EmployeeLogic" />

    <p>
    <asp:dropdownlist
      ID="DropDownList1"
      runat="server" 
      DataSourceID="ObjectDataSource1"
      DataTextField="FullName"
      DataValueField="EmployeeID" 
      AutoPostBack="True" 
      AppendDataBoundItems="true">
        <asp:ListItem Text="Select One" Value=""></asp:ListItem>
    </asp:dropdownlist>
    </p>

    <asp:objectdatasource
      ID="ObjectDataSource2"
      runat="server"
      SelectMethod="GetEmployee"
      UpdateMethod="UpdateEmployeeAddress"
      OnUpdating="EmployeeUpdating"
      OnSelected="EmployeeSelected"
      TypeName="Samples.AspNet.CS.EmployeeLogic" >
      <SelectParameters>
        <asp:ControlParameter ControlID="DropDownList1" DefaultValue="-1" Name="empID" />
      </SelectParameters>
    </asp:objectdatasource>
    
    <asp:DetailsView
        ID="DetailsView1"
        runat="server"
        DataSourceID="ObjectDataSource2" 
        AutoGenerateRows="false"
        AutoGenerateEditButton="true">  
        <Fields>
            <asp:BoundField HeaderText="Address" DataField="Address" />
            <asp:BoundField HeaderText="City" DataField="City" />
            <asp:BoundField HeaderText="Postal Code" DataField="PostalCode" />
        </Fields>  
    </asp:DetailsView>
   
</form>
<form id="form1" runat="server">

    <asp:objectdatasource
      ID="ObjectDataSource1"
      runat="server"
      SelectMethod="GetFullNamesAndIDs"
      TypeName="Samples.AspNet.CS.EmployeeLogic" />

    <p>
    <asp:dropdownlist
      ID="DropDownList1"
      runat="server" 
      DataSourceID="ObjectDataSource1"
      DataTextField="FullName"
      DataValueField="EmployeeID" 
      AutoPostBack="True" 
      AppendDataBoundItems="true">
        <asp:ListItem Text="Select One" Value=""></asp:ListItem>
    </asp:dropdownlist>
    </p>

    <asp:objectdatasource
      ID="ObjectDataSource2"
      runat="server"
      SelectMethod="GetEmployee"
      UpdateMethod="UpdateEmployeeAddress"
      OnUpdating="EmployeeUpdating"
      OnSelected="EmployeeSelected"
      TypeName="Samples.AspNet.CS.EmployeeLogic" >
      <SelectParameters>
        <asp:ControlParameter ControlID="DropDownList1" DefaultValue="-1" Name="empID" />
      </SelectParameters>
    </asp:objectdatasource>
    
    <asp:DetailsView
        ID="DetailsView1"
        runat="server"
        DataSourceID="ObjectDataSource2" 
        AutoGenerateRows="false"
        AutoGenerateEditButton="true">  
        <Fields>
            <asp:BoundField HeaderText="Address" DataField="Address" />
            <asp:BoundField HeaderText="City" DataField="City" />
            <asp:BoundField HeaderText="Postal Code" DataField="PostalCode" />
        </Fields>  
    </asp:DetailsView>
   
</form>

Nel secondo esempio vengono illustrati i gestori Selected per Updating gli eventi e.The second example shows handlers for the Selected and Updating events. Il Selected gestore eventi serializza l'oggetto contenente i dati recuperati dalla tabella Employee.The Selected event handler serializes the object that contains data that was retrieved from the Employee table. L'oggetto serializzato viene archiviato nello stato di visualizzazione.The serialized object is stored in view state. Il Updating gestore eventi deserializza l'oggetto nello stato di visualizzazione che contiene i dati originali per il record di dati da aggiornare.The Updating event handler deserializes the object in view state that contains the original data for the data record that is being updated. L'oggetto che contiene i dati originali viene passato come parametro al metodo Update.The object that contains the original data is passed as a parameter to the Update method. I dati originali devono essere passati al database in modo che possano essere utilizzati per verificare se i dati sono stati modificati da un altro processo.The original data must be passed to the database so that it can be used to check whether the data has been modified by another process.

public void EmployeeUpdating(object source, ObjectDataSourceMethodEventArgs e)
{
    DataContractSerializer dcs = new DataContractSerializer(typeof(Employee));

    String xmlData = ViewState["OriginalEmployee"].ToString();
    XmlReader reader = XmlReader.Create(new StringReader(xmlData));
    Employee originalEmployee = (Employee)dcs.ReadObject(reader);
    reader.Close();

    e.InputParameters.Add("originalEmployee", originalEmployee);
}

public void EmployeeSelected(object source, ObjectDataSourceStatusEventArgs e)
{
    if (e.ReturnValue != null)
    {
        DataContractSerializer dcs = new DataContractSerializer(typeof(Employee));
        StringBuilder sb = new StringBuilder();
        XmlWriter writer = XmlWriter.Create(sb);
        dcs.WriteObject(writer, e.ReturnValue);
        writer.Close();

        ViewState["OriginalEmployee"] = sb.ToString();
    }
}
Public Sub EmployeeUpdating(ByVal source As Object, ByVal e As ObjectDataSourceMethodEventArgs)
    Dim dcs As New DataContractSerializer(GetType(Employee))
    Dim xmlData As String
    Dim reader As XmlReader
    Dim originalEmployee As Employee

    xmlData = ViewState("OriginalEmployee").ToString()
    reader = XmlReader.Create(New StringReader(xmlData))
    originalEmployee = CType(dcs.ReadObject(reader), Employee)
    reader.Close()

    e.InputParameters.Add("originalEmployee", originalEmployee)
End Sub

Public Sub EmployeeSelected(ByVal source As Object, ByVal e As ObjectDataSourceStatusEventArgs)
    If e.ReturnValue IsNot Nothing Then
        Dim dcs As New DataContractSerializer(GetType(Employee))
        Dim sb As New StringBuilder()
        Dim writer As XmlWriter
        writer = XmlWriter.Create(sb)
        dcs.WriteObject(writer, e.ReturnValue)
        writer.Close()

        ViewState("OriginalEmployee") = sb.ToString()
    End If
End Sub

Nel terzo esempio viene illustrata la classe di accesso ai dati che interagisce con il database Northwind.The third example shows the data access class that interacts with the Northwind database. La classe utilizza LINQ per eseguire query e aggiornare la tabella Employees.The class uses LINQ to query and update the Employees table. Per l'esempio è necessaria una classe LINQ to SQL che rappresenti la tabella dei dipendenti e del database Northwind.The example requires a LINQ to SQL class that represents the Northwind database and Employees table. Per altre informazioni, vedere Procedura: Creare LINQ to SQL classi in un progettoWeb.For more information, see How to: Create LINQ to SQL Classes in a Web Project.

public class EmployeeLogic
{
    public static Array GetFullNamesAndIDs()
    {
        NorthwindDataContext ndc = new NorthwindDataContext();

        var employeeQuery =
            from e in ndc.Employees
            orderby e.LastName
            select new { FullName = e.FirstName + " " + e.LastName, EmployeeID = e.EmployeeID };

        return employeeQuery.ToArray();
    }

    public static Employee GetEmployee(int empID)
    {
        if (empID < 0)
        {
            return null;
        }
        else
        {
            NorthwindDataContext ndc = new NorthwindDataContext();
            var employeeQuery =
                from e in ndc.Employees
                where e.EmployeeID == empID
                select e;

            return employeeQuery.Single();
        }
    }
 
    public static void UpdateEmployeeAddress(Employee originalEmployee, string address, string city, string postalcode)
    {
        NorthwindDataContext ndc = new NorthwindDataContext();
        ndc.Employees.Attach(originalEmployee, false);
        originalEmployee.Address = address;
        originalEmployee.City = city;
        originalEmployee.PostalCode = postalcode;
        ndc.SubmitChanges();
    }
}
Public Class EmployeeLogic
    Public Shared Function GetFullNamesAndIDs() As Array
        Dim ndc As New NorthwindDataContext()

        Dim employeeQuery = _
            From e In ndc.Employees _
            Order By e.LastName _
            Select FullName = e.FirstName + " " + e.LastName, EmployeeID = e.EmployeeID

        Return employeeQuery.ToArray()
    End Function

    Public Shared Function GetEmployee(ByVal empID As Integer) As Employee

        If (empID < 0) Then
            Return Nothing
        Else
            Dim ndc As New NorthwindDataContext()
            Dim employeeQuery = _
                From e In ndc.Employees _
                Where e.EmployeeID = empID _
                Select e

            Return employeeQuery.Single()
        End If
    End Function

    Public Shared Sub UpdateEmployeeAddress(ByVal originalEmployee As Employee, ByVal address As String, ByVal city As String, ByVal postalcode As String)

        Dim ndc As New NorthwindDataContext()
        ndc.Employees.Attach(originalEmployee, False)
        originalEmployee.Address = address
        originalEmployee.City = city
        originalEmployee.PostalCode = postalcode
        ndc.SubmitChanges()
    End Sub
End Class

Commenti

Gestire l' Updating evento per eseguire un'inizializzazione aggiuntiva specifica per l'applicazione, per convalidare i valori dei parametri o per modificare i valori dei ObjectDataSource parametri prima che il controllo esegua l'operazione di aggiornamento.Handle the Updating event to perform additional initialization that is specific to your application, to validate the values of parameters, or to change the parameter values before the ObjectDataSource control performs the update operation. I parametri sono disponibili come IDictionary raccolta a cui si accede tramite la InputParameters proprietà, esposta dall' ObjectDataSourceMethodEventArgs oggetto.The parameters are available as an IDictionary collection that is accessed by the InputParameters property, which is exposed by the ObjectDataSourceMethodEventArgs object.

Per altre informazioni su come gestire gli eventi, vedere la gestione e generazione di eventi.For more information about how to handle events, see Handling and Raising Events.

Si applica a

Vedi anche