How to: Create a New Object using the Navigation Control

• Dec 22, 2023
• 4 minutes to read

This topic demonstrates how to execute custom code on a specific navigation item click. A navigation item that invokes the Detail View in Edit mode for an Issue object is added to the Navigation control.

Tip

A complete sample project is available in the DevExpress Code Examples database at https://supportcenter.devexpress.com/ticket/details/e236/xaf-how-to-show-a-new-object-detail-view-via-the-navigation-control.

In this example, the following Issue persistent class is used for demo purposes. You can use any other persistent class.

C# (EF Core)

using DevExpress.Persistent.Base;
using DevExpress.Persistent.BaseImpl.EF;
using System.ComponentModel.DataAnnotations;
// ...
[DefaultClassOptions, ImageName("BO_List")]
public class Issue : BaseObject {
    public virtual string Subject { get; set; }
    [FieldSize(FieldSizeAttribute.Unlimited)]
    public virtual string Description { get; set; }
}

// Make sure that you use options.UseChangeTrackingProxies() in your DbContext settings.

C# (XPO)

using DevExpress.Persistent.Base;
using DevExpress.Persistent.BaseImpl;
using DevExpress.Xpo;
// ...
[DefaultClassOptions, ImageName("BO_List")]
public class Issue : BaseObject {
    public Issue(Session session) : base(session) { }
    private string subject;
    public string Subject {
        get { return subject; }
        set { SetPropertyValue(nameof(Subject), ref subject, value); }
    }
    private string description;
    [Size(SizeAttribute.Unlimited)]
    public string Description {
        get { return description; }
        set { SetPropertyValue(nameof(Description), ref description, value); }
    }
}

VB.NET (XPO)

Imports DevExpress.Persistent.Base
Imports DevExpress.Persistent.BaseImpl
Imports DevExpress.Xpo
' ...
<DefaultClassOptions, ImageName("BO_List")> _
Public Class Issue
    Inherits BaseObject

    Public Sub New(ByVal session As Session)
        MyBase.New(session)
    End Sub
    Private _subject As String
    Public Property Subject() As String
        Get
            Return _subject
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(Subject), _subject, value)
        End Set
    End Property
    Private _description As String
    <Size(SizeAttribute.Unlimited)> _
    Public Property Description() As String
        Get
            Return _description
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(Description), _description, value)
        End Set
    End Property
End Class

To create a new object using the Navigation control, add a new navigation item and specify the code to be executed on this item click.

Add a new Navigation Item

To add a new navigation item, invoke the Model Editor for the module project by double-clicking the Model.DesignedDiffs.xafml file. Find the Issue navigation item node and add a new node to the same navigation group.

For this node, specify the properties from the table below with the corresponding values:

Property	Value
IModelBaseChoiceActionItem.Id	NewIssue
IModelBaseChoiceActionItem.Caption	Create New Issue…
IModelBaseChoiceActionItem.ImageName	Action_New
IModelNavigationItem.View	Issue_DetailView

Refer to the Add an Item to the Navigation Control topic to learn more about creating navigation items in the Model Editor.

Specify the Code to be Executed on a Navigation Item Click

To specify the code to be executed when the Create New Issue… navigation item is clicked, follow the steps below:

1. Create a Controller that is the WindowController descendant, override the OnActivated method, and subscribe to the ShowNavigationItemController.CustomShowNavigationItem event in this method. Use the Frame.GetController<ControllerType> method to access the ShowNavigationItemController instance.
2. In the CustomShowNavigationItem event handler, access the current navigation item identifier using the CustomShowNavigationItemEventArgs.ActionArguments event argument.

3. If the identifier is “NewIssue”, create the following objects using the corresponding methods from the table below:

   Object	Method
   Object Space	XafApplication.CreateObjectSpace
   Issue object	IObjectSpace.CreateObject
   Detail View for the Issue object	XafApplication.CreateDetailView

4. Set the Detail View’s DetailView.ViewEditMode property to ViewEditMode.Edit and specify that this View should be displayed using the ShowViewParameters.CreatedView property.
5. Since the Navigation control is displayed in the main Window only, the created Controller should be activated for the main Window as well by setting the WindowController.TargetWindowType property to Main in the Controller’s constructor.

C#

using DevExpress.ExpressApp;
using DevExpress.ExpressApp.SystemModule;
// ...
public class NewObjectFromNavigationController : WindowController {
    public NewObjectFromNavigationController() {
        TargetWindowType = WindowType.Main;
    }
    protected override void OnActivated() {
        base.OnActivated();
        ShowNavigationItemController showNavigationItemController = Frame.GetController<ShowNavigationItemController>();
        showNavigationItemController.CustomShowNavigationItem += showNavigationItemController_CustomShowNavigationItem;
    }
    void showNavigationItemController_CustomShowNavigationItem(object sender, CustomShowNavigationItemEventArgs e) {
        if (e.ActionArguments.SelectedChoiceActionItem.Id == "NewIssue") {
            IObjectSpace objectSpace = Application.CreateObjectSpace(typeof(Issue));
            Issue newIssue = objectSpace.CreateObject<Issue>();
            DetailView detailView = Application.CreateDetailView(objectSpace, newIssue);
            detailView.ViewEditMode = DevExpress.ExpressApp.Editors.ViewEditMode.Edit;
            e.ActionArguments.ShowViewParameters.CreatedView = detailView;
            e.Handled = true;
        }
    }
}

VB.NET

Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.SystemModule
' ...
Public Class NewObjectFromNavigationController
    Inherits WindowController

    Public Sub New()
        TargetWindowType = WindowType.Main
    End Sub
    Protected Overrides Sub OnActivated()
        MyBase.OnActivated()
        Dim showNavigationItemController As ShowNavigationItemController = Frame.GetController(Of ShowNavigationItemController)()
        AddHandler showNavigationItemController.CustomShowNavigationItem, _
AddressOf showNavigationItemController_CustomShowNavigationItem
    End Sub
    Private Sub showNavigationItemController_CustomShowNavigationItem(ByVal sender As Object, _
ByVal e As CustomShowNavigationItemEventArgs)
        If e.ActionArguments.SelectedChoiceActionItem.Id = "NewIssue" Then
            Dim objectSpace As IObjectSpace = Application.CreateObjectSpace(GetType(Issue))
            Dim newIssue As Issue = objectSpace.CreateObject(Of Issue)()
            Dim detailView As DetailView = Application.CreateDetailView(objectSpace, newIssue)
            detailView.ViewEditMode = DevExpress.ExpressApp.Editors.ViewEditMode.Edit
            e.ActionArguments.ShowViewParameters.CreatedView = detailView
            e.Handled = True
        End If
    End Sub
End Class

Run the WinForms, ASP.NET Web Forms, or ASP.NET Core Blazor application to check that the Issue objects can be created using the Create New Issue… navigation item (see the image at the beginning of this topic).