How to: Initialize an Object Created Using the New Action

• Oct 20, 2023
• 3 minutes to read

This topic describes how to access an object that is created using the New Action. Assume you are using the Task business class from the Business Class Library. When creating a new Task using the New Action, the Task.StartDate property will be set to the current date.

To access an object created using the New Action, handle the NewObjectViewController.ObjectCreated event of the NewObjectViewController that contains the New Action. To do this, implement a new View Controller. Override the Controller’s OnActivated method and subscribe to the ObjectCreated event in the following manner:

C#

using DevExpress.Persistent.BaseImpl;
using DevExpress.ExpressApp.SystemModule;
//...
public class MyController : ViewController {
    private NewObjectViewController controller;
    protected override void  OnActivated() {
        base.OnActivated();
        controller = Frame.GetController<NewObjectViewController>();
        if (controller != null) {
            controller.ObjectCreated += controller_ObjectCreated;
        }
    }
    void controller_ObjectCreated(object sender, ObjectCreatedEventArgs e) {
        if (e.CreatedObject is Task) {
            ((Task)e.CreatedObject).StartDate = DateTime.Now;
        }
    }
    protected override void OnDeactivated() {
        if (controller != null) {
            controller.ObjectCreated -= controller_ObjectCreated;
        }
        base.OnDeactivated();
    }
}

VB.NET

Imports DevExpress.Persistent.BaseImpl
Imports DevExpress.ExpressApp.SystemModule
'...
Public Class MyController
    Inherits ViewController
    Private controller As NewObjectViewController
    Protected Overrides Sub OnActivated()
        MyBase.OnActivated()
        controller = Frame.GetController(Of NewObjectViewController)()
        If controller IsNot Nothing Then
            AddHandler controller.ObjectCreated, AddressOf controller_ObjectCreated
        End If
    End Sub
    Private Sub controller_ObjectCreated(ByVal sender As Object, ByVal e As ObjectCreatedEventArgs)
        If TypeOf e.CreatedObject Is Task Then
            CType(e.CreatedObject, Task).StartDate = DateTime.Now
        End If
    End Sub
    Protected Overrides Sub OnDeactivated()
        If controller IsNot Nothing Then
            RemoveHandler controller.ObjectCreated, AddressOf controller_ObjectCreated
        End If
        MyBase.OnDeactivated()
    End Sub
End Class

In certain scenarios, it can be required to initialize a new object created through the lookup editor’s New button, using a value from the parent Detail View. To access the parent object from the ObjectCreated event handler, cast the Controller.Frame value to the NestedFrame type, access the NestedFrame.ViewItem property and then get the master object using the ViewItem.CurrentObject property.

C#

void controller_ObjectCreated(object sender, ObjectCreatedEventArgs e) {
    NestedFrame nestedFrame = Frame as NestedFrame;
    if (nestedFrame != null) {
        Item createdItem = e.CreatedObject as Item;
        if (createdItem != null) {
            Parent parent = ((NestedFrame)Frame).ViewItem.CurrentObject as Parent;
            if (parent != null) {
                createdItem.Title = parent.DefaultItemTitle;
            }
        }
    }
}

VB.NET

Private Sub controller_ObjectCreated(ByVal sender As Object, ByVal e As ObjectCreatedEventArgs)
    Dim nestedFrame As NestedFrame = TryCast(Frame, NestedFrame)
    If nestedFrame IsNot Nothing Then
        Dim createdItem As Item = TryCast(e.CreatedObject, Item)
        If createdItem IsNot Nothing Then
            Dim parent As Parent = TryCast(CType(Frame, NestedFrame).ViewItem.CurrentObject, Parent)
            If parent IsNot Nothing Then
                createdItem.Title = parent.DefaultItemTitle
            End If
        End If
    End If
End Sub