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ObjectDataSource.Update Method

Performs an update operation by calling the method that is identified by the UpdateMethod property and any parameters that are in the UpdateParameters collection.

Namespace:  System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

'Declaration
Public Function Update As Integer

Return Value

Type: System.Int32
A value that represents the number of rows updated in the underlying data storage.

The business object is assumed to update data one record at a time, rather than in a batch.

Before the Update operation is performed, the OnUpdating method is called to raise the Updating event. You can handle the Updating event to examine the values of the parameters and to perform any preprocessing before an Update operation. To perform an update operation, the ObjectDataSourceView object uses reflection to create an instance of the object that is identified by the TypeName property. It then calls the method that is identified by the UpdateMethod property, using any associated UpdateParameters properties. After the Update operation completes, the OnUpdated method is called to raise the Updated event. You can handle the Updated event to examine any return values, output parameters, and exceptions, and to perform any post-processing.

The Update method delegates to the Update method of the ObjectDataSourceView that is associated with the ObjectDataSource control.

For more information about parameter merging, object lifetime, and method resolution, see UpdateMethod.

Security noteSecurity Note

You should validate any parameter value that you receive from the client. The runtime simply substitutes the parameter value into the UpdateMethod property.

Data-Bound Controls

When the ObjectDataSource control is associated with a data-bound control, such as the GridView control, it is not necessary to call the Update method from page code. The Update method is invoked directly by the data-bound control instead.

This section contains two code examples. The first code example demonstrates how to use a DropDownList control, TextBox controls, and several ObjectDataSource objects to update data. The second code example shows the EmployeeLogic class that is used in the first code example.

The following code example demonstrates how to use a DropDownList control, TextBox controls, and several ObjectDataSource controls to update data. The DropDownList displays the name of a Northwind employee, while the TextBox controls are used to enter and update address information. Because the UpdateParameters collection contains a ControlParameter object that is bound to the selected value of the DropDownList, the button that raises the Update operation is enabled only after an employee is selected.

Security noteSecurity Note

This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %>
<%@ Page language="vb" %>
<%@ Import namespace="Samples.AspNet.VB" %>

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

' Add parameters and initialize the user interface
' only if an employee is selected.
Private Sub Page_Load(sender As Object, e As EventArgs)

  ' Be sure the text boxes are initialized with
  ' data from the currently selected employee.
  Dim selectedEmployee As NorthwindEmployee
  selectedEmployee = EmployeeLogic.GetEmployee(DropDownList1.SelectedValue)

  If Not selectedEmployee Is Nothing Then
    AddressBox.Text    = selectedEmployee.Address
    CityBox.Text       = selectedEmployee.City
    PostalCodeBox.Text = selectedEmployee.PostalCode

    Button1.Enabled = True
  Else
    Button1.Enabled = False
  End If
End Sub ' Page_Load

' Press the button to update.
Private Sub Btn_UpdateEmployee (sender As Object, e As CommandEventArgs )
  ObjectDataSource2.Update()
End Sub ' Btn_UpdateEmployee

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>ObjectDataSource - VB Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <!-- The DropDownList is bound to the first ObjectDataSource. -->
        <asp:objectdatasource
          id="ObjectDataSource1"
          runat="server"
          selectmethod="GetAllEmployees"
          typename="Samples.AspNet.VB.EmployeeLogic" />

        <p><asp:dropdownlist
          id="DropDownList1"
          runat="server"
          datasourceid="ObjectDataSource1"
          datatextfield="FullName"
          datavaluefield="EmpID"
          autopostback="True" /></p>

        <!-- The second ObjectDataSource performs the Update. This
             preserves the state of the DropDownList, which otherwise
             would rebind when the DataSourceChanged event is
             raised as a result of an Update operation. -->

        <!-- Security Note: The ObjectDataSource uses a FormParameter,
             Security Note: which does not perform validation of input from the client.
             Security Note: To validate the value of the FormParameter,
             Security Note: handle the Updating event. -->

        <asp:objectdatasource
          id="ObjectDataSource2"
          runat="server"
          updatemethod="UpdateEmployeeWrapper"
          typename="Samples.AspNet.VB.EmployeeLogic">
          <updateparameters>
            <asp:controlparameter name="anID" controlid="DropDownList1" propertyname="SelectedValue" />
            <asp:formparameter name="anAddress" formfield="AddressBox" />
            <asp:formparameter name="aCity" formfield="CityBox" />
            <asp:formparameter name="aPostalCode" formfield="PostalCodeBox" />
          </updateparameters>
        </asp:objectdatasource>

        <p><asp:textbox
          id="AddressBox"
          runat="server" /></p>

        <p><asp:textbox
          id="CityBox"
          runat="server" /></p>

        <p><asp:textbox
          id="PostalCodeBox"
          runat="server" /></p>

        <asp:button
          id="Button1"
          runat="server"
          text="Update Employee"
          oncommand="Btn_UpdateEmployee" />

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

The following code example shows the EmployeeLogic class that is used in the preceding code example.

Imports System
Imports System.Collections
Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.UI
Imports System.Web.UI.WebControls

Namespace Samples.AspNet.VB

' EmployeeLogic is a stateless business object that encapsulates 
' the operations one can perform on a NorthwindEmployee object. 

Public Class EmployeeLogic

   ' Returns a collection of NorthwindEmployee objects. 
   Public Shared Function GetAllEmployees() As ICollection
      Dim al As New ArrayList()

      ' Use the SqlDataSource class to wrap the 
      ' ADO.NET code required to query the database. 
      Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection")
      Dim sds As New SqlDataSource(cts.ConnectionString, _
                                  "SELECT EmployeeID FROM Employees")
      Try 
         Dim IDs As IEnumerable = sds.Select(DataSourceSelectArguments.Empty)

         ' Iterate through the Enumeration and create a 
         ' NorthwindEmployee object for each ID. 
         Dim enumerator As IEnumerator = IDs.GetEnumerator()
         While enumerator.MoveNext()
            ' The IEnumerable contains DataRowView objects. 
            Dim row As DataRowView = CType(enumerator.Current,DataRowView)
            Dim id As String = row("EmployeeID").ToString()
            Dim nwe As New NorthwindEmployee(id)
            ' Add the NorthwindEmployee object to the collection.
            al.Add(nwe)
         End While 
      Finally 
         ' If anything strange happens, clean up.
         sds.Dispose()
      End Try 

      Return al
   End Function 'GetAllEmployees


   Public Shared Function GetEmployee(anID As Object) As NorthwindEmployee
      Dim al As ArrayList = CType(GetAllEmployees(), ArrayList)
      Dim enumerator As IEnumerator = al.GetEnumerator()
      While enumerator.MoveNext()
         ' The IEnumerable contains initialized NorthwindEmployee objects. 
         Dim ne As NorthwindEmployee = CType(enumerator.Current,NorthwindEmployee)
         If ne.EmpID.Equals(anID.ToString()) Then 
            Return ne
         End If 
      End While 
      Return Nothing 
   End Function 'GetEmployee

   Public Shared Sub UpdateEmployee(ne As NorthwindEmployee)
      Dim retval As Boolean = ne.Update()
      If Not retval Then 
         Throw New NorthwindDataException("Employee update failed.")
      End If 
   End Sub 'UpdateEmployee

   ' This method is added as a conveniece wrapper on the original 
   ' implementation. 
   Public Shared Sub UpdateEmployeeWrapper(anID As String, _
                                           anAddress As String, _
                                           aCity As String, _
                                           aPostalCode As String)
      Dim ne As New NorthwindEmployee(anID)
      ne.Address = anAddress
      ne.City = aCity
      ne.PostalCode = aPostalCode
      UpdateEmployee(ne)
   End Sub 'UpdateEmployeeWrapper
   ' And so on... 

End Class 'EmployeeLogic

Public Class NorthwindEmployee

   Public Sub New(anID As Object)
      Me.ID = anID
      Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection")
      Dim conn As New SqlConnection(cts.ConnectionString)
      Dim sc As New SqlCommand(" SELECT FirstName,LastName,Address,City,PostalCode " & _
                               " FROM Employees " & _
                               " WHERE EmployeeID = @empId", conn)

      ' Add the employee ID parameter and set its value.
      sc.Parameters.Add(New SqlParameter("@empId", SqlDbType.Int)).Value = Int32.Parse(anID.ToString())
      Dim sdr As SqlDataReader = Nothing 

      Try
         conn.Open()
         sdr = sc.ExecuteReader()

         ' This is not a while loop. It only loops once. 
         If Not (sdr Is Nothing) AndAlso sdr.Read() Then 
            ' The IEnumerable contains DataRowView objects. 
            Me.aFirstName = sdr("FirstName").ToString()
            Me.aLastName = sdr("LastName").ToString()
            Me.aAddress = sdr("Address").ToString()
            Me.aCity = sdr("City").ToString()
            Me.aPostalCode = sdr("PostalCode").ToString()
         Else 
            Throw New NorthwindDataException("Data not loaded for employee id.")
         End If 
      Finally 
         Try 
            If Not (sdr Is Nothing) Then
               sdr.Close()
            End If
            conn.Close()
         Catch se As SqlException
            ' Log an event in the Application Event Log. 
            Throw 
         End Try 
      End Try 
   End Sub 'New 

   Private ID As Object 
   Public ReadOnly Property EmpID() As Object 
      Get 
         Return ID
      End Get 
   End Property 

   Private aLastName As String 
   Public WriteOnly Property LastName() As String 
      Set
         aLastName = value
      End Set 
   End Property 

   Private aFirstName As String 
   Public WriteOnly Property FirstName() As String 
      Set
         aFirstName = value
      End Set 
   End Property 

   Public ReadOnly Property FullName() As String 
      Get 
         Return aFirstName & " " & aLastName
      End Get 
   End Property 

   Private aAddress As String 
   Public Property Address() As String 
      Get 
         Return aAddress
      End Get 
      Set
         aAddress = value
      End Set 
   End Property 

   Private aCity As String 
   Public Property City() As String 
      Get 
         Return aCity
      End Get 
      Set
         aCity = value
      End Set 
   End Property 

   Private aPostalCode As String 
   Public Property PostalCode() As String 
      Get 
         Return aPostalCode
      End Get 
      Set
         aPostalCode = value
      End Set 
   End Property 

   Public Function Update() As Boolean 

      ' Implement Update logic. 
      Return True 

   End Function 'Update

End Class 'NorthwindEmployee

Friend Class NorthwindDataException
   Inherits Exception

   Public Sub New(msg As String)
      MyBase.New(msg)
   End Sub 'New 

End Class 'NorthwindDataException
End Namespace

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0
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