How to: Subscribe to Events in a .NET Framework Type

With .NET Framework interoperability in Microsoft Dynamics NAV objects, you can configure a DotNet variable to subscribe to events that are published by a .NET Framework type. Events are handled by triggers in the C/AL code of the Microsoft Dynamics NAV object. To configure a DotNet variable to subscribe to events published by a .NET Framework class, you set the WithEvents Property of the DotNet variable. A trigger is automatically added in the C/AL code for each event that is exposed by the .NET Framework type. For more information about events in NET Framework Interoperability, see Handling Events.

To subscribe to events published by a .NET Framework type

1. In the development environment, open the Microsoft Dynamics NAV object that uses .NET Framework interoperability, and then open the C/AL code.

2. On the View menu, choose C/AL Globals.

3. On the Variables tab, select the DotNet variable, and then on the View menu, choose Properties.

4. In the Properties window, set the WithEvents property to Yes.

   For each event that is exposed by the .NET Framework class, a blank trigger is added to the C/AL code. The triggers have the following format.

   DotNetVariable :: Event (sender : Variant;e DotNet "EventArgs")
   

   • DotNetVariable is the name of the DotNet variable that subscribes to the event.

   • Event is the name of the event published by the .NET Framework class

   • () will contain any parameters that the event has.

5. Add code to the event triggers to handle the events.

Example

The following code example implements a simple synchronous event that will invoke a C/AL trigger without any parameters. You will create a .NET Framework assembly that contains the event, and then subscribe to the event in the C/AL code of a Microsoft Dynamics NAV codeunit.

To create and deploy the assembly that includes an event

1. In Visual Studio, create a C# class library project that is called MyEvent.

2. Add the following code that implements the ChangedEvent event in the EventsNoArgs class.

   namespace MyEvent
   {
       public class EventsNoArgs
       {
           public delegate void ChangedEventHandler();
           public event ChangedEventHandler ChangedEvent;
           // Invoke the ChangedEvent
           protected virtual void OnChangedEvent()
           {
               if (ChangedEvent != null)
               {
                   ChangedEvent();
               }
           }
           // The following method is exposed to C/AL and will invoke the event trigger that is registered in the ChangedEvent variable. 
           public void FireEvent()
           {
               OnChangedEvent();
           }
       }
   }
   

3. Build the project.

4. Copy the MyEvent.dll file to the computer that is running the Microsoft Dynamics NAV development environment. You must copy the assembly to the Add-ins folder of the Microsoft Dynamics NAV Windows client and Microsoft Dynamics NAV Server installation folders. The default path of the Microsoft Dynamics NAV Windows client installation folder is C:\Program Files\Microsoft Dynamics NAV\71\RoleTailored Client or C:\Program Files (x86)\Microsoft Dynamics NAV\71RoleTailored Client. The default path of the Microsoft Dynamics NAV Server installation folder is C:\Program Files\Microsoft Dynamics NAV\71\Service.

To subscribe to the event in C/AL

1. In the development environment, create a new codeunit.

2. Create the following global C/AL variables.

   Variable name	DataType	SubType
   eventVar	DotNet	MyEvent.EventsNoArgs
   counter	Integer

3. Open the properties for the eventVAR variable, and then set the WithEvents Property to Yes.

   The eventVar::ChangedEvent() trigger is added to the C/AL.

4. On the OnRun trigger, add the following code.

   //Reset the global counter to zero.
   counter := 0;
   // Construct the DotNet object that implements the event.
   eventVar := eventVar.EventsNoArgs();
   // Fire the event three times.
   eventVar.FireEvent();
   eventVar.FireEvent();
   eventVar.FireEvent();
   // Inspect the counter and raise an error if the count does not match the number of events fired.
   if counter <> 3 then error(‘Unexpected count value, %1’, counter);
   message(‘Received %1 events’, counter);
   

5. On the eventVar::ChangedEvent() trigger, add the following code to increment the counter variable.

   counter += 1;
   

6. Save and compile the codeunit.

7. To test the event, in Object Designer, select the codeunit, and then choose Run.

   The Microsoft Dynamics NAV Windows client opens and the message “Received 3 events” appears.

   If you remove one of the eventVar.FireEvent(); statements, and then compile and run the codeunit again, you will get an error message.

See Also

Concepts

Handling Events with Microsoft .NET Framework Interoperability
Extending Microsoft Dynamics NAV Using Microsoft .NET Framework Interoperability
Calling .NET Framework Members from C/AL