How to: Use Notifications with a Custom Business Class (Implement ISupportNotifications)

• Jul 08, 2021
• 6 minutes to read

This example demonstrates how to associate Notifications with the custom business class.

Tip

A complete sample project is available in the DevExpress Code Examples database at https://supportcenter.devexpress.com/ticket/details/t177793/how-to-use-notifications-with-a-custom-business-class-implement-isupportnotifications.

Note

• This example is for the Entity Framework data model. If you use XPO, refer to the Notifications | Custom Entity With Notifications example in the Feature Center demo. The Feature Center demo is installed in %PUBLIC%\Documents\DevExpress Demos 20.2\Components.NET Core Desktop Libraries\eXpressApp Framework\FeatureCenter by default. The ASP.NET Web Forms version of this demo is available online at https://demos.devexpress.com/XAF/FeatureCenter/.
• Blazor applications do not support the Notifications Module.

Assume you have the following Task business class.

C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using DevExpress.Persistent.Base;
// ...
[DefaultClassOptions]
 public class Task : INotifyPropertyChanged {
     private int id;
    [Browsable(false)]
    public int Id { get; private set; }

    private string subject;
    public string Subject { 
        get { return subject; } 
        set { SetProperty<string>(ref subject, value); } 
    }

    private DateTime dueDate;
    public DateTime DueDate { 
        get { return dueDate; }
        set { SetProperty<DateTime>(ref dueDate, value);}
    }

    protected void SetProperty<T>(ref T field, T value, [CallerMemberName] string propertyName = null) {
        if(!EqualityComparer<T>.Default.Equals(field, value)) {
            field = value;
            OnPropertyChanged(propertyName);
        }
    }
    #region INotifyPropertyChanged members
    protected void OnPropertyChanged(string propertyName) {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
    public event PropertyChangedEventHandler PropertyChanged;
    #endregion
}

VB.NET

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Runtime.CompilerServices
Imports DevExpress.Persistent.Base
' ...
<DefaultClassOptions>
Public Class Task 
    Implements INotifyPropertyChanged
    Private privateId As Integer
    <Browsable(False)>
    Public Property Id() As Integer
        Get
            Return privateId
        End Get
        Private Set(ByVal value As Integer)
            privateId = value
        End Set
    End Property

    Private _subject As String
    Public Property Subject() As String
        Get
            Return _subject
        End Get
        Set(value As String)
            SetProperty(Of String)(_subject, value)
        End Set
    End Property

    Private _dueDate As Date
    Public Property DueDate() As Date
        Get
            Return _dueDate
        End Get
        Set(value As Date)
            SetProperty(Of Date)(_dueDate, value)
        End Set
    End Property

    Protected Sub SetProperty(Of T)(ByRef field As T, ByVal value As T, <CallerMemberName> Optional ByVal propertyName As String = Nothing)
        If (Not EqualityComparer(Of T).[Default].Equals(field, value)) Then
            field = value
            OnPropertyChanged(propertyName)
        End If
    End Sub
#Region "INotifyPropertyChanged"
    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
    Protected Sub OnPropertyChanged(ByVal propertyName As String)
        PropertyChangedEvent?.Invoke(Me, New PropertyChangedEventArgs(propertyName))
    End Sub
#End Region
End Class

The goal is to notify a user before the DueDate moment arrives using functionality provided by the Notifications Module. Follow the steps below:

1. Add this module’s components to your projects using the Module Designer:

   • Add the NotificationsModule to your Module project.

     

   • Add the NotificationsModuleWeb to your Module.Web project.

     

   • Add the NotificationsModuleWin to your Module.Win project.

     

   Note

   By default, the notification refresh interval is 5 minutes. For testing purposes, you may reduce this interval. Double-click the WinApplication.cs(vb) file from the Win application project, select the NotificationsModule in the Modules section of the Module Designer. In the Properties window, set the NotificationsModule.NotificationsRefreshInterval to 10 seconds. Do the same for the WebApplication.cs(vb) file from the Web application project.

2. Implement the ISupportNotifications interface in the Task class.

   C#

   using DevExpress.Persistent.Base.General;
   // ...
   [DefaultClassOptions]
   public class Task : INotifyPropertyChanged, ISupportNotifications {
       // ...
   
       #region ISupportNotifications members
       private DateTime? alarmTime;
       [Browsable(false)]
       public DateTime? AlarmTime {
           get { return alarmTime; }
           set {
               SetProperty<DateTime?>(ref alarmTime, value);
               if (value == null) {
                   RemindIn = null;
                   IsPostponed = false;
               }
           }
       }
       private bool isPostponed;
       [Browsable(false)]
       public bool IsPostponed {
           get { return isPostponed;}
           set { SetProperty<bool>(ref isPostponed, value);}
       }
   
       [Browsable(false), NotMapped]
       public string NotificationMessage {
           get { return Subject; }
       }
   
       private TimeSpan? remindIn;
       public TimeSpan? RemindIn {
           get { return remindIn; }
           set { SetProperty<TimeSpan?>(ref remindIn, value); }
       }
   
       [Browsable(false), NotMapped]
       public object UniqueId {
           get { return Id; }
       }
       #endregion
   }
   

   VB.NET

   Imports DevExpress.Persistent.Base.General
   ' ...
   <DefaultClassOptions>
   Public Class Task
       Implements INotifyPropertyChanged, ISupportNotifications
       ' ...
       #Region "ISupportNotifications members"
       Private _alarmTime? As Date
       <Browsable(False)> _
       Public Property AlarmTime() As Date? Implements ISupportNotifications.AlarmTime
           Get
               Return _alarmTime
           End Get
           Set(ByVal value? As Date)
               SetProperty(Of Date?)(_alarmTime, value)
               If value Is Nothing Then
                   RemindIn = Nothing
                   IsPostponed = False
               End If
           End Set
       End Property
   
       Private _isPostponed As Boolean
           <Browsable(False)>
           Public Property IsPostponed() As Boolean Implements ISupportNotifications.IsPostponed
               Get
                   Return _isPostponed
               End Get
               Set(value As Boolean)
                   SetProperty(Of Boolean)(_isPostponed, value)
               End Set
           End Property
   
       <Browsable(False), NotMapped>
       Public ReadOnly Property NotificationMessage() As String Implements ISupportNotifications.NotificationMessage
           Get
               Return Subject
           End Get
       End Property
   
       Private _remindIn As TimeSpan?
           Public Property RemindIn() As TimeSpan?
               Get
                   Return _remindIn
               End Get
               Set(value As TimeSpan?)
                   SetProperty(Of TimeSpan?)(_remindIn, value)
               End Set
           End Property
   
       <Browsable(False), NotMapped>
       Public ReadOnly Property UniqueId() As Object Implements ISupportNotifications.UniqueId
           Get
               Return Id
           End Get
       End Property
       #End Region
   End Class
   

3. Implement IXafEntityObject to provide the logic that initializes the AlarmTime according to the RemindIn interval specified by the user. Here is an example logic implemented in the OnSaving method.

   C#

   using DevExpress.ExpressApp;
   // ...
   [DefaultClassOptions]
   public class Task : INotifyPropertyChanged, ISupportNotifications, IXafEntityObject {
       // ...
       #region IXafEntityObject members
       public void OnCreated() { }
       public void OnLoaded() { }
       public void OnSaving() {
           if(RemindIn.HasValue) {
               if((AlarmTime == null) || (AlarmTime < DueDate - RemindIn.Value)) {
                   AlarmTime = DueDate - RemindIn.Value;
               }
           }
           else {
               AlarmTime = null;
           }
           if (AlarmTime == null) {
               RemindIn = null;
               IsPostponed = false;
           }
       }
       #endregion
   }
   

   VB.NET

   Imports DevExpress.ExpressApp
   ' ...
   <DefaultClassOptions>
   Public Class Task
       Implements INotifyPropertyChanged, ISupportNotifications, IXafEntityObject
       ' ...
       #Region "IXafEntityObject members"
       Public Sub OnCreated() Implements IXafEntityObject.OnCreated
       End Sub
       Public Sub OnLoaded() Implements IXafEntityObject.OnLoaded
       End Sub
       Public Sub OnSaving() Implements IXafEntityObject.OnSaving
           If RemindIn.HasValue Then
               If (AlarmTime Is Nothing) OrElse (AlarmTime < DueDate - RemindIn.Value) Then
                   AlarmTime = DueDate - RemindIn.Value
               End If
           Else
               AlarmTime = Nothing
           End If
           If AlarmTime Is Nothing Then
               RemindIn = Nothing
               IsPostponed = False
           End If
       End Sub
       #End Region
   End Class
   

Run the WinForms or ASP.NET application and create a new overdue Task in the past (the DueDate should be earlier than the current time). Specify a non-empty value for the RemindIn property that specifies the amount of time between the notification alert and the DueDate moment (empty RemindIn value means that the alert is never displayed).

Save the task and you will see the Reminder window after the time span specified via the NotificationsModule.NotificationsRefreshInterval property or less.