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ObjectDataSourceStatusEventArgs Class

Note: This class is new in the .NET Framework version 2.0.

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

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

public class ObjectDataSourceStatusEventArgs : EventArgs
public class ObjectDataSourceStatusEventArgs extends EventArgs
public class ObjectDataSourceStatusEventArgs extends EventArgs

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

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#" %>
<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>
  <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>

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.DeleteCommand = "DELETE FROM Employees WHERE EmployeeID=@empID";
          sds.DeleteParameters.Add(new Parameter("empID",TypeCode.Int32,this.ID.ToString()));

          //
          // Implement the remainder of the Delete() method.
          //
          throw new NorthwindDataException("Delete() method not completely implemented.");
        }
        finally {
          // Clean up resources.
          sds.Dispose();
        }
      }
    }
  }

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

System.Object
   System.EventArgs
    System.Web.UI.WebControls.ObjectDataSourceStatusEventArgs

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

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