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

• Jun 10, 2024
• 4 minutes to read

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

Assume you have the following MyTask business class.

Entity Framework Core

using System;
using System.Collections.Generic;
using System.ComponentModel;
using DevExpress.Persistent.Base;
using DevExpress.Persistent.BaseImpl.EF;

namespace MySolution.Module.BusinessObjects;
[DefaultClassOptions]
 public class MyTask : BaseObject {
    public virtual string Subject { get; set; }
    public virtual DateTime DueDate { get; set; }
}

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

XPO

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using DevExpress.Persistent.Base;
using DevExpress.Persistent.BaseImpl;
using DevExpress.Xpo;

namespace MySolution.Module.BusinessObjects;
[DefaultClassOptions]
public class MyTask : BaseObject {
    public MyTask(Session session) : base(session) { }
    public string Subject {
        get {
            return GetPropertyValue<string>(nameof(Subject));
        }
        set {
            SetPropertyValue(nameof(Subject), value);
        }
    }
    public DateTime DueDate {
        get {
            return GetPropertyValue<DateTime>(nameof(DueDate));
        }
        set {
            SetPropertyValue(nameof(DueDate), value);
        }
    }
}

The goal is to use the functionality of the Notifications module to send a reminder to a user before the DueDate.

1. Add the Notifications module to your application.

   Note

   The default notification refresh interval is 5 minutes, but you can reduce this interval for testing purposes. For more information, refer to the following topic: How to Specify the Notification Refresh Frequency

2. Implement the ISupportNotifications interface in the MyTask class.

   Entity Framework Core

   using DevExpress.Persistent.Base.General;
   using DevExpress.Persistent.BaseImpl.EF;
   // ...
   [DefaultClassOptions]
   public class MyTask : BaseObject, ISupportNotifications {
       // ...
       #region ISupportNotifications members
       private DateTime? alarmTime;
       [Browsable(false)]
       public virtual DateTime? AlarmTime { 
           get { return alarmTime; }
           set {
               if (value == null) {
                   RemindIn = null;
                   IsPostponed = false;
               }
               alarmTime = value;
           }
       }
   
       [Browsable(false)]
       public virtual bool IsPostponed { get; set; }
   
       [Browsable(false),NotMapped]
       public string NotificationMessage {
           get { return Subject; }
       }
       public virtual TimeSpan? RemindIn { get; set; }
   
       [Browsable(false),NotMapped]
       public object UniqueId {
           get { return ID; }
       }
       #endregion
   }
   
   // Make sure that you use options.UseChangeTrackingProxies() in your DbContext settings.
   

   XPO

   using System;
   using System.Collections.Generic;
   using System.ComponentModel.DataAnnotations.Schema;
   using System.ComponentModel;
   using System.Linq;
   using System.Text;
   using System.Threading.Tasks;
   using DevExpress.Persistent.Base;
   using DevExpress.Persistent.Base.General;
   using DevExpress.Persistent.BaseImpl;
   using DevExpress.Xpo;
   
   namespace MySolution.Module.BusinessObjects;
   [DefaultClassOptions]
   public class MyTask : BaseObject, ISupportNotifications {
   
       #region ISupportNotifications members
       private DateTime? alarmTime;
       [Browsable(false)]
       public DateTime? AlarmTime {
           get { return alarmTime; }
           set {
               if(value == null) {
                   RemindIn = null;
                   IsPostponed = false;
               }
               SetPropertyValue(nameof(AlarmTime), ref alarmTime, value);
           }
       }
   
       [Browsable(false)]
       public bool IsPostponed {
           get {
               return GetPropertyValue<bool>(nameof(IsPostponed));
           }
           set {
               SetPropertyValue(nameof(IsPostponed), value);
           }
       }
   
       [Browsable(false)]
       public string NotificationMessage {
           get { return Subject; }
       }
       public TimeSpan? RemindIn {
           get {
               return GetPropertyValue<TimeSpan?>(nameof(RemindIn));
           }
           set {
               SetPropertyValue(nameof(RemindIn), value);
           }
       }
   
       [Browsable(false)]
       public object UniqueId {
           get { return Oid; }
       }
       #endregion
   }
   

3. Override the OnSaving method to initialize AlarmTime based on the RemindIn interval specified by a user.

   Entity Framework Core

   using DevExpress.ExpressApp;
   // ...
   [DefaultClassOptions]
   public class MyTask : BaseObject, ISupportNotifications {
       // ...
       #region IXafEntityObject members
       public override 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
   }
   
   // Make sure that you use options.UseChangeTrackingProxies() in your DbContext settings.
   

   XPO

   // ...
   using DevExpress.Xpo;
   
   namespace MySolution.Module.BusinessObjects;
   [DefaultClassOptions]
   public class MyTask : BaseObject, ISupportNotifications {
       // ...
       protected override void OnSaving() {
           base.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;
           }
       }
   }
   

4. Run the 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 defines the time between the notification alert and the DueDate moment (an empty RemindIn value means that the alert is never displayed).

   

5. Save the task. The Notifications window should appear after the time span specified in the NotificationsOptionsBase.NotificationsRefreshInterval property or sooner.