How to: Show Notifications to a Specific User

• Jun 23, 2021
• 3 minutes to read

By default, notifications are displayed to all users. This example demonstrates how to filter notifications in order to display the reminders window only to a required user.

Note

• This example is based on the Entity Framework data model, but you can use the same approach with the eXpress Persistent Objects (XPO) as well.

• ASP.NET Core Blazor applications do not support the Notifications Module.

Assume you have the ISupportNotifications business object exposing the AssignedTo property.

C#

[DefaultClassOptions]
public class Task : ISupportNotifications, IXafEntityObject {
    // ...
    public virtual Employee AssignedTo { get; set; }
}

VB.NET

<DefaultClassOptions> _
Public Class Task
    Implements ISupportNotifications, IXafEntityObject
    ' ...
    Public Overridable Property AssignedTo() As Employee
End Class

Here, we consider the Task business class implemented in the How to: Use Notifications with a Custom Business Class (Implement ISupportNotifications) example. The Employee is a custom Security System user type that is in a one-to-many association with Tasks.

C#

using System.ComponentModel;
using DevExpress.Persistent.Base;
// ...
[DefaultClassOptions, DefaultProperty(nameof(UserName))]
public class Employee : DevExpress.Persistent.BaseImpl.EF.User {
    public Employee() {
        Tasks = new List<Task>();
    }
    public virtual IList<Task> Tasks { get; set; }
}

VB.NET

Imports System.ComponentModel
Imports DevExpress.Persistent.Base
' ...
<DefaultClassOptions, DefaultProperty(NameOf(UserName))> _
Public Class Employee
    Inherits DevExpress.Persistent.BaseImpl.EF.User

    Public Sub New()
        Tasks = New List(Of Task)()
    End Sub
    Public Overridable Property Tasks() As IList(Of Task)
End Class

Edit the Module.cs (Module.vb) file. In the overridden ModuleBase.Setup method, subscribe to the XafApplication.LoggedOn event. In this event handler, get the NotificationsModule instance and subscribe to the DefaultNotificationsProvider.CustomizeNotificationCollectionCriteria event.

C#

using DevExpress.Data.Filtering;
using DevExpress.ExpressApp.Notifications;
using DevExpress.Persistent.Base.General;
// ...
public override void Setup(XafApplication application) {
    base.Setup(application);
    application.LoggedOn += application_LoggedOn;
}
void application_LoggedOn(object sender, LogonEventArgs e) {
   NotificationsModule notificationsModule = Application.Modules.FindModule<NotificationsModule>();
   DefaultNotificationsProvider notificationsProvider = notificationsModule.DefaultNotificationsProvider;
   notificationsProvider.CustomizeNotificationCollectionCriteria += notificationsProvider_CustomizeNotificationCollectionCriteria;
}
void notificationsProvider_CustomizeNotificationCollectionCriteria(
    object sender, CustomizeCollectionCriteriaEventArgs e) {
    if (e.Type == typeof(Task)) {
        e.Criteria = CriteriaOperator.Parse("AssignedTo is null || AssignedTo.Id == CurrentUserId()");
    }
}

VB.NET

Imports DevExpress.Data.Filtering
Imports DevExpress.ExpressApp.Notifications
Imports DevExpress.Persistent.Base.General
' ...
Public Overrides Sub Setup(ByVal application As XafApplication)
    MyBase.Setup(application)
    AddHandler application.LoggedOn, AddressOf application_LoggedOn
End Sub
Private Sub application_LoggedOn(ByVal sender As Object, ByVal e As LogonEventArgs)
    Dim notificationsModule As NotificationsModule = Application.Modules.FindModule(Of NotificationsModule)()
    Dim notificationsProvider As DefaultNotificationsProvider = notificationsModule.DefaultNotificationsProvider
    AddHandler notificationsProvider.CustomizeNotificationCollectionCriteria, AddressOf notificationsProvider_CustomizeNotificationCollectionCriteria
End Sub
Private Sub notificationProvider_CustomizeNotificationCollectionCriteria(ByVal sender As Object, ByVal e As CustomizeCollectionCriteriaEventArgs)
    If e.Type Is GetType(Task) Then
        e.Criteria = CriteriaOperator.Parse("AssignedTo is null || AssignedTo.Id == CurrentUserId()")
    End If
End Sub

As a result, a notification will be displayed only if the AssignedTo value is empty or refers to the current user.

If you use the scheduler event descendant instead of a custom ISupportNotifications object, use the SchedulerModuleBase.NotificationsProvider property to access the NotificationsProvider object and handle the NotificationsProvider.CustomizeNotificationCollectionCriteria event.

C#

using DevExpress.ExpressApp.Scheduler;
// ...
void application_LoggedOn(object sender, LogonEventArgs e) {
    SchedulerModuleBase schedulerModule = Application.Modules.FindModule<SchedulerModuleBase>();
    NotificationsProvider notificationsProvider = schedulerModule.NotificationsProvider;
    notificationsProvider.CustomizeNotificationCollectionCriteria += notificationsProvider_CustomizeNotificationCollectionCriteria;
}

VB.NET

Imports DevExpress.ExpressApp.Scheduler
' ...
Private notificationsProvider As NotificatonsProvider
Private Sub application_LoggedOn(ByVal sender As Object, ByVal e As LogonEventArgs)
    Dim schedulerModule As SchedulerModuleBase = Application.Modules.FindModule(Of SchedulerModuleBase)()
    Dim notificationsProvider As NotificationsProvider = schedulerModule.NotificationsProvider
    AddHandler notificationsProvider.CustomizeNotificationCollectionCriteria, AddressOf notificationsProvider_CustomizeNotificationCollectionCriteria
End Sub