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ObjectDataSourceStatusEventArgs Class

  • Reference

Definition

Namespace:
System.Web.UI.WebControls
Assembly:
System.Web.dll

Provides data for the Selected, Inserted, Updated, and Deleted events of the ObjectDataSource control.

public ref class ObjectDataSourceStatusEventArgs : EventArgs
public class ObjectDataSourceStatusEventArgs : EventArgs
type ObjectDataSourceStatusEventArgs = class
    inherit EventArgs
Public Class ObjectDataSourceStatusEventArgs
Inherits EventArgs
Inheritance
Object
EventArgs
ObjectDataSourceStatusEventArgs

Examples

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.CS" Assembly="Samples.AspNet.CS" %>
<%@ Import namespace="Samples.AspNet.CS" %>
<%@ Page language="c#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
private void NorthwindEmployeeDeleting(object source, ObjectDataSourceMethodEventArgs e)
{
  // The GridView passes the ID of the employee
  // to be deleted. However, the buisiness object, EmployeeLogic,
  // requires a NorthwindEmployee parameter, named "ne". Create
  // it now and add it to the parameters collection.
  IDictionary paramsFromPage = e.InputParameters;
  if (paramsFromPage["EmpID"] != null) {
    NorthwindEmployee ne
      = new NorthwindEmployee( Int32.Parse(paramsFromPage["EmpID"].ToString()));
    // Remove the old EmpID parameter.
    paramsFromPage.Clear();
    paramsFromPage.Add("ne", ne);
  }
}

private void NorthwindEmployeeDeleted(object source, ObjectDataSourceStatusEventArgs e)
{
  // Handle the Exception if it is a NorthwindDataException
  if (e.Exception != null)
  {

    // Handle the specific exception type. The ObjectDataSource wraps
    // any Exceptions in a TargetInvokationException wrapper, so
    // check the InnerException property for expected Exception types.
    if (e.Exception.InnerException is NorthwindDataException)
    {
      Label1.Text = e.Exception.InnerException.Message;
      // Because the exception is handled, there is
      // no reason to throw it.
      e.ExceptionHandled = true;
    }
  }
}

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>ObjectDataSource - C# 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.CS.EmployeeLogic">
          <deleteparameters>
            <asp:parameter name="EmpID" type="Int32" />
          </deleteparameters>
        </asp:objectdatasource>

        <asp:label id="Label1" runat="server" />

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

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %>
<%@ Import namespace="Samples.AspNet.VB" %>
<%@ Page language="vb" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<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 xmlns="http://www.w3.org/1999/xhtml" >
  <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:

  • The EmployeeLogic class is a class that does not maintain state and encapsulates business logic.

  • 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.

namespace Samples.AspNet.CS {

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web.UI;
using System.Web.UI.WebControls;
  //
  // EmployeeLogic is a stateless business object that encapsulates
  // the operations you can perform on a NorthwindEmployee object.
  //
  public class EmployeeLogic {

    // Returns a collection of NorthwindEmployee objects.
    public static ICollection GetAllEmployees () {
      ArrayList al = new ArrayList();

      // Use the SqlDataSource class to wrap the
      // ADO.NET code required to query the database.
      ConnectionStringSettings cts = ConfigurationManager.ConnectionStrings["NorthwindConnection"];

      SqlDataSource sds
        = new SqlDataSource(cts.ConnectionString,
                            "SELECT EmployeeID FROM Employees");
      try {
        IEnumerable IDs = sds.Select(DataSourceSelectArguments.Empty);

        // Iterate through the Enumeration and create a
        // NorthwindEmployee object for each ID.
        IEnumerator enumerator = IDs.GetEnumerator();
        while (enumerator.MoveNext()) {
          // The IEnumerable contains DataRowView objects.
          DataRowView row = enumerator.Current as DataRowView;
          string id = row["EmployeeID"].ToString();
          NorthwindEmployee nwe = new NorthwindEmployee(id);
          // Add the NorthwindEmployee object to the collection.
          al.Add(nwe);
        }
      }
      finally {
        // If anything strange happens, clean up.
        sds.Dispose();
      }

      return al;
    }

    public static NorthwindEmployee GetEmployee(object anID) {
      return new NorthwindEmployee(anID);
    }

    public static void DeleteEmployee(NorthwindEmployee ne) {
      bool retval = ne.Delete();
      if (! retval) { throw new NorthwindDataException("Employee delete failed."); }
      // Delete the object in memory.
      ne = null;
    }

    public static void DeleteEmployeeByID(int anID) {
        NorthwindEmployee tempEmp = new NorthwindEmployee(anID);
        DeleteEmployee(tempEmp);
    }
  }

  public class NorthwindEmployee {

    public NorthwindEmployee () {
      ID = DBNull.Value;
      lastName = "";
      firstName = "";
    }

    public NorthwindEmployee (object anID) {
      this.ID = anID;

      ConnectionStringSettings cts = ConfigurationManager.ConnectionStrings["NorthwindConnection"];

      SqlConnection conn = new SqlConnection (cts.ConnectionString);
      SqlCommand sc =
        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());
      SqlDataReader sdr = null;

      try {
        conn.Open();
        sdr = sc.ExecuteReader();

        // This is not a while loop. It only loops once.
        if (sdr != null && sdr.Read()) {
          // The IEnumerable contains DataRowView objects.
          this.firstName        = sdr["FirstName"].ToString();
          this.lastName         = sdr["LastName"].ToString();
        }
        else {
          throw new NorthwindDataException("Data not loaded for employee id.");
        }
      }
      finally {
        try {
          if (sdr != null) sdr.Close();
          conn.Close();
        }
        catch (SqlException) {
          // Log an event in the Application Event Log.
          throw;
        }
      }
    }

    private object ID;
    public object EmpID {
      get { return ID; }
    }

    private string lastName;
    public string LastName {
      get { return lastName; }
      set { lastName = value; }
    }

    private string firstName;
    public string FirstName {
      get { return firstName; }
      set { firstName = value;  }
    }
    public bool Delete () {
      if (ID.Equals(DBNull.Value)) {
        // 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.
        ConnectionStringSettings cts = ConfigurationManager.ConnectionStrings["NorthwindConnection"];
        SqlDataSource sds = new SqlDataSource();

        try {
          sds.ConnectionString = cts.ConnectionString;
          sds.DeleteParameters.Add(new Parameter("empID", TypeCode.Int32, this.ID.ToString()));
          sds.DeleteCommand = "DELETE FROM [Order Details] " + 
              "WHERE OrderID IN (SELECT OrderID FROM Orders WHERE EmployeeID=@empID)";
          sds.Delete();
          sds.DeleteCommand = "DELETE FROM Orders WHERE EmployeeID=@empID";
          sds.Delete();
          sds.DeleteCommand = "DELETE FROM EmployeeTerritories WHERE EmployeeID=@empID";
          sds.Delete();
          sds.DeleteCommand = "DELETE FROM Employees WHERE EmployeeID=@empID";
          sds.Delete();
          return true;
        }
        finally {
          // Clean up resources.
          sds.Dispose();
        }
      }
    }
  }

  public class NorthwindDataException: Exception {
    public NorthwindDataException(string msg) : base (msg) { }
  }
}

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


   Public Shared Sub DeleteEmployeeByID(anID As Integer)
      Dim tempEmp As New NorthwindEmployee(anID)
      DeleteEmployee(tempEmp)
   End Sub

End Class

Public Class NorthwindEmployee

   Public Sub New()
      ID = DBNull.Value
      aLastName = ""
      aFirstName = ""
   End Sub


   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

   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.DeleteParameters.Add(New Parameter("empID", TypeCode.Int32, Me.ID.ToString()))
            sds.DeleteCommand = "DELETE FROM [Order Details] " & _
                "WHERE OrderID IN (SELECT OrderID FROM Orders WHERE EmployeeID=@empID)"
            sds.Delete()
            sds.DeleteCommand = "DELETE FROM Orders WHERE EmployeeID=@empID"
            sds.Delete()
            sds.DeleteCommand = "DELETE FROM EmployeeTerritories WHERE EmployeeID=@empID"
            sds.Delete()
            sds.DeleteCommand = "DELETE FROM Employees WHERE EmployeeID=@empID"
            sds.Delete()
            Return True
         Finally
            ' Clean up resources.
            sds.Dispose()
         End Try
      End If
   End Function 'Delete
End Class

Public Class NorthwindDataException
   Inherits Exception

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

End Class
End Namespace

Remarks

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
ObjectCreating.

Occurs immediately before the instance of the business object is created.		 ObjectDataSourceEventArgs ObjectDataSourceObjectEventHandler
ObjectCreated.

Occurs immediately after the instance of the business object is created.		 ObjectDataSourceEventArgs ObjectDataSourceObjectEventHandler
Selecting.

Occurs before the data is retrieved.		 ObjectDataSourceSelectingEventArgs ObjectDataSourceSelectingEventHandler
Inserting, Updating, and Deleting.

Occur before an insert, update, or delete operation is performed.		 ObjectDataSourceMethodEventArgs ObjectDataSourceMethodEventHandler
Selected.

Occurs after the data is retrieved.		 ObjectDataSourceStatusEventArgs ObjectDataSourceStatusEventHandler
Inserted, Updated, and Deleted.

Occur after the insert, update, or delete operation is completed.		 ObjectDataSourceStatusEventArgs ObjectDataSourceStatusEventHandler
ObjectDisposing.

Occurs before a business object is destroyed.		 ObjectDataSourceDisposingEventArgs ObjectDataSourceDisposingEventHandler

Constructors

ObjectDataSourceStatusEventArgs(Object, IDictionary, Exception)

Initializes a new instance of the ObjectDataSourceStatusEventArgs class using the specified output parameters, return value, and exception.
ObjectDataSourceStatusEventArgs(Object, IDictionary)

Initializes a new instance of the ObjectDataSourceStatusEventArgs class using the specified output parameters and return value.

Properties

AffectedRows

Gets or sets the number of rows that are affected by the data operation.
Exception

Gets a wrapper for any exceptions that are thrown by the method that is called by the ObjectDataSource control during a data operation.
ExceptionHandled

Gets or sets a value indicating whether an exception that was thrown by the business object has been handled.
OutputParameters

Gets a collection that contains business object method parameters and their values.
ReturnValue

Gets the return value that is returned by the business object method, if any, as an object.

Methods

Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
ToString()

Returns a string that represents the current object.

(Inherited from Object)

Applies to

See also