ObjectDataSourceEventArgs Class
Definition
Important
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Provides data for the ObjectCreating and ObjectCreated events of the ObjectDataSource control.
public ref class ObjectDataSourceEventArgs : EventArgspublic class ObjectDataSourceEventArgs : EventArgstype ObjectDataSourceEventArgs = class
inherit EventArgsPublic Class ObjectDataSourceEventArgs
Inherits EventArgs- Inheritance
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 retrieve and display information. The second code example provides the example basic 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 retrieve and display information. In this example, as in many real-world scenarios, it might not be possible nor appropriate to use a default instance of the business object with the ObjectDataSource control. In this example, the ObjectDataSource cannot successfully call the parameterless constructor because it will throw an exception. In some cases, the parameterless constructor might be protected and in others it might not initialize the business object to a desired state. Whatever the reason, you can create an instance of the business object yourself and set the instance to the ObjectInstance property of the ObjectDataSourceEventArgs object that is passed to the handler. This is the business object instance that the ObjectDataSource will use to perform its work.
<%@ 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 NorthwindLogicCreating(object sender, ObjectDataSourceEventArgs e)
{
// Create an instance of the business object using a non-default constructor.
EmployeeLogic eLogic = new EmployeeLogic("Not created by the default constructor!");
// Set the ObjectInstance property so that the ObjectDataSource uses the created instance.
e.ObjectInstance = eLogic;
}
</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">
</asp:gridview>
<asp:objectdatasource
id="ObjectDataSource1"
runat="server"
selectmethod="GetAllEmployees"
onobjectcreating="NorthwindLogicCreating"
typename="Samples.AspNet.CS.EmployeeLogic" >
</asp:objectdatasource>
</form>
</body>
</html>
<%@ 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">
Private Sub NorthwindLogicCreating(sender As Object, e As ObjectDataSourceEventArgs)
' Create an instance of the business object using a non-default constructor.
Dim eLogic As EmployeeLogic = New EmployeeLogic("Not created by the default constructor!")
' Set the ObjectInstance property so that the ObjectDataSource uses the created instance.
e.ObjectInstance = eLogic
End Sub ' NorthwindLogicCreating
</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">
</asp:gridview>
<asp:objectdatasource
id="ObjectDataSource1"
runat="server"
selectmethod="GetAllEmployees"
onobjectcreating="NorthwindLogicCreating"
typename="Samples.AspNet.VB.EmployeeLogic" >
</asp:objectdatasource>
</form>
</body>
</html>
The following code example demonstrates the example basic business object that the preceding code example uses.
namespace Samples.AspNet.CS {
using System;
using System.Collections;
using System.Web.UI;
using System.Web.UI.WebControls;
public class EmployeeLogic {
public EmployeeLogic() {
throw new NotSupportedException("Initialize data.");
}
public EmployeeLogic(string data) {
_data = data;
}
private string _data;
// Returns a collection of NorthwindEmployee objects.
public ICollection GetAllEmployees () {
ArrayList al = new ArrayList();
al.Add(_data);
return al;
}
}
}
Imports System.Collections
Imports System.Web.UI
Imports System.Web.UI.WebControls
Namespace Samples.AspNet.VB
Public Class EmployeeLogic
Public Sub New()
Throw New NotSupportedException("Initialize data.")
End Sub
Public Sub New(ByVal data As String)
_data = data
End Sub
Private _data As String
' Returns a collection of NorthwindEmployee objects.
Public Function GetAllEmployees() As ICollection
Dim al As New ArrayList()
al.Add(_data)
Return al
End Function 'GetAllEmployees
End Class
End Namespace ' Samples.AspNet.VB
Remarks
The ObjectDataSourceEventArgs class is used in the OnObjectCreating and OnObjectCreated methods to provide access to the business object instance before any data operations that are using the ObjectDataSource control and business object are performed. The business object is set and accessed using the ObjectInstance property. By adding an event handler delegate to handle the ObjectCreating event, you can create an instance of the business object in custom code instead of the ObjectDataSource performing the instantiation. This is useful when you want a non-default instance of your business object or to call a non-parameterless constructor to create the instance; the ObjectDataSource always calls the parameterless constructor to create an instance of the business object it works with. You can also add an event handler delegate to handle the ObjectCreated event, which enables you to access any publicly exposed members of the business object to perform any additional initialization or work.
The OnObjectCreating and OnObjectCreated methods are not called by the ObjectDataSource control, if the business object method that performs the data operations is static.
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.
Constructors
| ObjectDataSourceEventArgs(Object) |
Initializes a new instance of the ObjectDataSourceEventArgs class using the specified object. |
Properties
| ObjectInstance |
Gets or sets an object that represents the business object with which the ObjectDataSource control performs data operations. |
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) |
