ObjectDataSource.Updating Kejadian
Definisi
Penting
Beberapa informasi terkait produk prarilis yang dapat diubah secara signifikan sebelum dirilis. Microsoft tidak memberikan jaminan, tersirat maupun tersurat, sehubungan dengan informasi yang diberikan di sini.
Terjadi sebelum Update() operasi.
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 Jenis Acara
Contoh
Tiga contoh berikut menunjukkan halaman Web, kelas halaman di belakang kode, dan kelas akses data yang memungkinkan pengguna untuk mengambil dan memperbarui rekaman dalam tabel Karyawan di database Northwind.
Contoh pertama memperlihatkan halaman Web yang berisi dua ObjectDataSource kontrol, DropDownList kontrol, dan DetailsView kontrol. Kontrol pertama ObjectDataSource dan DropDownList kontrol digunakan untuk mengambil dan menampilkan nama karyawan dari database. Kontrol kedua ObjectDataSource dan DetailsView kontrol digunakan untuk mengambil, menampilkan, dan memodifikasi data dari rekaman karyawan yang dipilih oleh pengguna.
<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>
Contoh kedua menunjukkan handler untuk Selected peristiwa dan Updating . Penanganan Selected aktivitas menserialisasikan objek yang berisi data yang diambil dari tabel Karyawan. Objek yang diserialisasikan disimpan dalam status tampilan. Penanganan Updating aktivitas mendeserialisasi objek dalam status tampilan yang berisi data asli untuk rekaman data yang sedang diperbarui. Objek yang berisi data asli diteruskan sebagai parameter ke metode Perbarui. Data asli harus diteruskan ke database sehingga dapat digunakan untuk memeriksa apakah data telah dimodifikasi oleh proses lain.
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
Contoh ketiga memperlihatkan kelas akses data yang berinteraksi dengan database Northwind. Kelas menggunakan LINQ untuk mengkueri dan memperbarui tabel Karyawan. Contohnya memerlukan kelas LINQ ke SQL yang mewakili database Northwind dan tabel Karyawan. Untuk informasi selengkapnya, lihat Cara: Membuat LINQ ke Kelas SQL di Proyek Web.
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
Keterangan
Updating Tangani peristiwa untuk melakukan inisialisasi tambahan yang khusus untuk aplikasi Anda, untuk memvalidasi nilai parameter, atau untuk mengubah nilai parameter sebelum ObjectDataSource kontrol melakukan operasi pembaruan. Parameter tersedia sebagai IDictionary koleksi yang diakses oleh InputParameters properti , yang diekspos oleh ObjectDataSourceMethodEventArgs objek .
Untuk informasi selengkapnya tentang cara menangani peristiwa, lihat Menangani dan Menaikkan Peristiwa.
