Notification is a way of SOLIDWORKS to tell its listeners that something has happened. When developing applications or macros using SOLIDWORKS API it might be required to trigger certain functionality (i.e. run certain code) when some event happens. For example, you might want to update custom property when new document is created or write a log message on file is closing.

There are much more events exposed by SOLIDWORKS, this includes but not limited to feature creation, document save, objects selection etc.

Below is a list of SOLIDWORKS interfaces which expose events and the corresponding links to the API help documentation:

In this blog article I will show how to handle file open event in VBA, C# and VB.NET

We will display a simple message box with the full path to the opened document once the event is triggered.

Document opened message box
Document opened message box

Handling events in VBA Macros

To handle events in VBA it is required to declare the object which exposes the events using the WithEvents keyword. This keyword can only be used in class modules and not available in modules.

Once the object is declared with WithEvents keyword, its events can be selected from the drop-down in the VBA Editor.

List of SOLIDWORKS events
List of SOLIDWORKS events

Select the required event and implement the code within the generated event handler function.

Dim WithEvents swApp As SldWorks.SldWorks

Private Sub Class_Initialize()
    Set swApp = Application.SldWorks
End Sub

Private Function swApp_FileOpenNotify2(ByVal FileName As String) As Long
    swApp.SendMsgToUser2 FileName & " opened", swMessageBoxIcon_e.swMbInformation, swMessageBoxBtn_e.swMbOk
    swApp_FileOpenNotify2 = 0
End Function

The class which handles the events could be instantiated in the main module once the macro runs.

VBA project tree
VBA project tree
Dim swEventsHandler As EventsHandler

Sub main()
    Set swEventsHandler = New EventsHandler

End Sub

Handling events in C# Applications

When developing C# applications events can be handled by using the += operator and specifying the handler function. Handler function must match the signature of event’s delegate.

Use {Tab}{Tab} combination in Visual Studio to automatically generate event handler with the correct signature.

It is recommended to unsubscribe from the event on closing of the application. This can be done by calling the -= operator.

Note it is required to use versions of the interfaces without I at the beginning as I-methods do not expose events (i.e. use SldWorks instead of ISldWorks).

using SolidWorks.Interop.sldworks;
using SolidWorks.Interop.swconst;
using System;

namespace CodeStack
    class Program
        private static SldWorks m_App;

        static void Main(string[] args)
            m_App = Activator.CreateInstance(Type.GetTypeFromProgID("SldWorks.Application")) as SldWorks;
            m_App.Visible = true;

            m_App.FileOpenNotify2 += OnFileOpenNotify2;


            m_App.FileOpenNotify2 -= OnFileOpenNotify2;

        private static int OnFileOpenNotify2(string fileName)
            m_App.SendMsgToUser2($"{fileName} opened", (int)swMessageBoxIcon_e.swMbInformation, (int)swMessageBoxBtn_e.swMbOk);
            return 0;

Handling events in VB.NET Applications

VB.NET allows to subscribe to events using the AddHandler keyword and providing the reference to the handler function using the AddressOf keyword. Event can be unsubscribed using the RemoveHandler keyword.

Imports SolidWorks.Interop.sldworks
Imports SolidWorks.Interop.swconst

Module Module1

    Dim m_App As SldWorks

    Sub Main()

        m_App = TryCast(Activator.CreateInstance(Type.GetTypeFromProgID("SldWorks.Application")), SldWorks)
        m_App.Visible = True

        AddHandler m_App.FileOpenNotify2, AddressOf OnFileOpenNotify2


        RemoveHandler m_App.FileOpenNotify2, AddressOf OnFileOpenNotify2

    End Sub

    Function OnFileOpenNotify2(ByVal fileName As String) As Integer
        m_App.SendMsgToUser2($"{fileName} opened", CInt(swMessageBoxIcon_e.swMbInformation), CInt(swMessageBoxBtn_e.swMbOk))
        Return 0
    End Function

End Module

Handling events in SwEx.AddIn Framework

SOLIDWORKS doesn’t group document events under the common IModelDoc2 interface, and in most cases provides similar or the same event for part, assembly and drawing. It is required to explicitly handle this case in your application.

To handle events of documents it required to catch the document loading events of SldWorks interface first and subscribe to target events within its handler.

SwEx.AddIn framework significantly simplifies managing of document events via its document management mechanism.

For example the following code would handle rebuild operations (pre and post) for all types of documents currently loaded or newly created or opened in the SOLIDWORKS session.

private IDocumentsHandler<DocumentHandler> m_DocHandlerGeneric;

public override bool OnConnect()
	m_DocHandlerGeneric = CreateDocumentsHandler();
	m_DocHandlerGeneric.HandlerCreated += OnHandlerCreated;
	return true;

private void OnHandlerCreated(DocumentHandler doc)
	doc.Rebuild += OnRebuild;

private bool OnRebuild(DocumentHandler docHandler, RebuildState_e type)
    //TODO: implement handler for rebuilding
    return true;