ObjectDataSourceStatusEventArgs Class
Assembly: System.Web (in system.web.dll)
The ObjectDataSourceStatusEventArgs class is used in the OnSelected, OnUpdated, OnInserted, and OnDeleted methods to provide access to output parameters, return values, and exceptions that are thrown by the method that is called by the ObjectDataSource control. These are accessed by the OutputParameters, ReturnValue, and Exception properties, respectively. By adding a delegate to handle the Selected, Updated, Inserted, or Deleted events, you can examine this data and perform any additional post processing that is required.
The ObjectDataSource control exposes many events that you can handle to work with the underlying business object at various times in its lifecycle. The following table lists the events and the associated EventArgs classes and event handler delegates.
| Event | EventArgs | EventHandler |
|---|---|---|
| Occurs immediately before the instance of the business object is created. | ||
| Occurs immediately after the instance of the business object is created. | ObjectDataSourceEventArgs | ObjectDataSourceObjectEventHandler |
| Occurs before the data is retrieved. | ||
| Inserting, Updating, and Deleting. Occur before an insert, update, or delete operation is performed. | ||
| Selected. Occurs after the data is retrieved. | ObjectDataSourceStatusEventArgs | |
| Inserted, Updated, and Deleted. Occur after the insert, update, or delete operation is completed. | ObjectDataSourceStatusEventArgs | ObjectDataSourceStatusEventHandler |
| Occurs before a business object is destroyed. |
This section contains two code examples. The first code example demonstrates how to use an ObjectDataSource control with a business object and a GridView control to delete data. The second code example provides an example middle-tier business object that the first code example uses.
The following code example demonstrates how to use an ObjectDataSource control with a business object and a GridView control to delete data. The GridView initially displays a set of all employees, using the method that is specified by the SelectMethod property to retrieve the data from the EmployeeLogic object. Because the AutoGenerateDeleteButton property is set to true, the GridView control automatically displays a Delete button.
If you click the Delete button, the Delete action is performed using the method that is specified by the DeleteMethod property and any parameters that are specified in the DeleteParameters collection. In this code example, one parameter is specified in the DeleteParameters collection that corresponds to the employee ID. This is because although the ID is included in the Columns collection as a BoundField object, it will be passed as a string to the ObjectDataSource control. By adding it explicitly to the DeleteParameters collection with a Type property set to the Int32 value, it will pass correctly by the ObjectDataSource to the method as an integer, rather than as string.
In this code example, some preprocessing and post-processing steps are also performed. The NorthwindEmployeeDeleting delegate is called to handle the Deleting event before the Delete action is performed, and the NorthwindEmployeeDeleted delegate is called to handle the Deleted event after the Delete action has completed, to handle any exceptions that might have occurred. The NorthwindEmployeeDeleted delegate accesses possible exceptions that are thrown by the business object that is using the ObjectDataSourceStatusEventArgs object. In this example, if a NorthwindDataException is thrown, it is handled by this delegate.
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %> <%@ Import namespace="Samples.AspNet.VB" %> <%@ Page language="vb" %> <Script runat="server"> ' Called before a Delete operation. Private Sub NorthwindEmployeeDeleting(ByVal source As Object, ByVal e As ObjectDataSourceMethodEventArgs) ' The GridView passes the ID of the employee ' to be deleted. However, the business object, EmployeeLogic, ' requires a NorthwindEmployee parameter, named "ne". Create ' it now and add it to the parameters collection. Dim paramsFromPage As IDictionary = e.InputParameters If Not paramsFromPage("EmpID") Is Nothing Then Dim ne As New NorthwindEmployee(paramsFromPage("EmpID").ToString()) ' Remove the old EmpID parameter. paramsFromPage.Clear() paramsFromPage.Add("ne", ne) End If End Sub ' NorthwindEmployeeDeleting ' Called after a Delete operation. Private Sub NorthwindEmployeeDeleted(ByVal source As Object, ByVal e As ObjectDataSourceStatusEventArgs) ' Handle the Exception if it is a NorthwindDataException. If Not e.Exception Is Nothing Then ' Handle the specific exception type. The ObjectDataSource wraps ' any Exceptions in a TargetInvokationException wrapper, so ' check the InnerException property for the expected Exception types. If e.Exception.InnerException.GetType().Equals(GetType(NorthwindDataException)) Then Label1.Text = e.Exception.InnerException.Message ' Because the exception is handled, there is ' no reason to throw it. e.ExceptionHandled = True End If End If End Sub ' NorthwindEmployeeDeleted </Script> <html> <head> <title>ObjectDataSource - VB Example</title> </head> <body> <form id="Form1" method="post" runat="server"> <asp:gridview id="GridView1" runat="server" datasourceid="ObjectDataSource1" autogeneratedeletebutton="true" autogeneratecolumns="false" datakeynames="EmpID"> <columns> <asp:boundfield headertext="EmpID" datafield="EmpID" /> <asp:boundfield headertext="First Name" datafield="FirstName" /> <asp:boundfield headertext="Last Name" datafield="LastName" /> </columns> </asp:gridview> <asp:objectdatasource id="ObjectDataSource1" runat="server" selectmethod="GetAllEmployees" deletemethod="DeleteEmployee" ondeleting="NorthwindEmployeeDeleting" ondeleted="NorthwindEmployeeDeleted" typename="Samples.AspNet.VB.EmployeeLogic"> <deleteparameters> <asp:parameter name="EmpID" type="Int32" /> </deleteparameters> </asp:objectdatasource> <asp:label id="Label1" runat="server" /> </form> </body> </html>
The following code example provides an example middle-tier business object that the preceding code example uses. The following list describes the two major classes that are defined in the code example:
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The EmployeeLogic class is a class that does not maintain state and encapsulates business logic.
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The NorthwindEmployee class is a model class that contains only the basic functionality that is required to load and persist data from the data tier.
In addition, a NorthwindDataException class is provided as a convenience.
This set of example classes uses the Northwind Traders database, which is an example database that is available with Microsoft SQL Server and Microsoft Access. For a complete working example, you must compile this code as a library, and then use these classes from an ASP page. The ASP page that is provided in the preceding example is configured to work with this class library. The UpdateEmployeeInfo method is not completely implemented, so you will not insert data into the Northwind Traders database when you experiment with this 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 you can perform on a NorthwindEmployee object. Public Class EmployeeLogic ' Return 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 Return New NorthwindEmployee(anID) End Function 'GetEmployee Public Shared Sub DeleteEmployee(ne As NorthwindEmployee) Dim retval As Boolean = ne.Delete() If Not retval Then Throw New NorthwindDataException("Employee delete failed.") End If ' Delete the object in memory. ne = Nothing End Sub 'DeleteEmployee Public Shared Sub DeleteEmployeeByID(anID As Integer) Dim tempEmp As New NorthwindEmployee(anID) DeleteEmployee(tempEmp) End Sub 'DeleteEmployeeByID End Class 'EmployeeLogic Public Class NorthwindEmployee Public Sub New() ID = DBNull.Value aLastName = "" aFirstName = "" End Sub 'New 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 " & _ " 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() 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 Property LastName() As String Get Return aLastName End Get Set aLastName = value End Set End Property Private aFirstName As String Public Property FirstName() As String Get Return aFirstName End Get Set aFirstName = value End Set End Property Public Function Delete() As Boolean If ID.Equals(DBNull.Value) Then ' The Employee object is not persisted. Return True Else ' The Employee object is persisted. ' Use the SqlDataSource control as a convenient wrapper for ' the ADO.NET code needed to delete a record from the database. Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection") Dim sds As New SqlDataSource() Try sds.ConnectionString = cts.ConnectionString sds.DeleteCommand = "DELETE FROM Employees WHERE EmployeeID=@empID" sds.DeleteParameters.Add(New Parameter("empID", TypeCode.Int32, Me.ID.ToString())) ' Implement the remainder of the Delete() method. ' Throw New NorthwindDataException("Delete() method not completely implemented.") Return True Finally ' Clean up resources. sds.Dispose() End Try End If End Function 'Delete End Class 'NorthwindEmployee Public Class NorthwindDataException Inherits Exception Public Sub New(msg As String) MyBase.New(msg) End Sub 'New End Class 'NorthwindDataException End Namespace
- AspNetHostingPermission for operating in a hosted environment. Demand value: LinkDemand; Permission value: Minimal.
- AspNetHostingPermission for operating in a hosted environment. Demand value: InheritanceDemand; Permission value: Minimal.
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