My First Plugin - Lesson 3 C# issue

[scottmoyse]

It looks like the Lesson 3 C# code sample is incomplete, there's no private void (equivalent of a private sub from VB?) Form1_FormClosed, as a result Inventor doesn't close correctly when the form is closed. I've written the code like this:

private void Form1_FormClosed(object sender, System.Windows.Forms.FormClosedEventArgs e)
        {
            if (_started)
                _invApp.Quit();
            _invApp = (Inventor.Application)null;
        }

but it doesn't work. It runs/compiles error free, but when I close the form Inventor doesn't close. The VB sample has 'ByVar' in the sub argument (inside the brackets). I wondering if I shoudl be using a C# equivalent here, I just don't know what it is. I appreciate any help that can be given here.

[scottmoyse]

Ok so I see ByVal isn't the problem because everything is passed as By Value in C#, So somethign else is missing instead..... 

[scottmoyse · Accepted solution]

Yippee I got it working. It looks like its a terminology issue:

VB = Closed

C# = Closing

This is the code that should be in the C# sample code

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (_started)
                _invApp.Quit();
            _invApp = (Inventor.Application)null;
        }

Note I'm uncertain about the _invApp = (Inventor.Application)null; line of code. I commented it out and it didn't seem to make any difference. Is it just good practice to have it there? in case _invApp is used again in another method later on within this class?

 Can someone involved in the My FIrst Plugin program fix this up please?

[Qube-it]

Scott, 

Without looking at the rest of the code, I'm assuming that _invApp is already declared as a private variable of type Application.Inventor and that this code is essentially being called when a close event (perhaps on some form that is part of a stand-alone application that controls Inventor?) is being fired.

With that said, the setting of the _invApp to null is doing just what you're thinking (i.e. making sure that nothing else in that class can do anything with it). If anything else did happen to call it then there would be a null reference exception thrown and you would most likely know about it. Since your calling the Quit() method inside a method that handles a Form Closing event, I would venture a guess that the entire class will fall out of scope since it's attached to the Form that's closing. Let's put it this way, you probably don't need it but it won't hurt anything to set it to null.

As an aside, you shouldn't have to cast the null to Inventor.Application since _invApp is (more than likely) already that type. In other words, if you left that last line of code in there you can remove the casting of Inventor.Application. Like so...

private void Form1_FormClosed(object sender, System.Windows.Vorms.FormClosedEventArgs e)
{
    if(_started)
        _invApp.Quit();
    _invApp = null;
}

[scottmoyse]

you assume correctly & confirm my understanding which is awesome. I cast to Inventor.Application cos the sample code did it further up. Even though _invApp had already been assigned to that type. I thought it was unnecessary there as well but since I'm a noob I rolled with it. This makes me feel good 🙂 I'm starting to get it.

Cheers for your time Brian

[wayne.brill]

Hi Scott,

I see the _invApp.Quit(); method is called when Form1 is disposed. (in Form1.Designer.cs) If you put a break point on this line does it get hit when you close the Form? (It does in my tests if launching the form started Inventor) 

protectedoverridevoid Dispose(bool disposing)

        {

if (disposing && (components != null))

            {

                components.Dispose();

            }

base.Dispose(disposing);

//Test to see if we started the Inventor Application.

//If Inventor was started by running this form then call the

//Quit method.

if (_started)

            {

                _invApp.Quit();

            }

            _invApp =

null;

        }

[scottmoyse]

Wayne,

thank you for your reply.

You had me confused there for a while. I couldn't see where the dispose calls were, then I realised the code you had posted was from two seperate tabs/windows.

Yes when I place a stop on that line it gets hit. I see it then moves onto the disposing stuff after that, even though the Inventor process isn't showing up in the task manager anymore.

Is it just empyting the memory? How does it know what to clear out? Can you explain a bit more about this dispose method please?

[wayne.brill]

Hi Scott,

When I created that Visual Studio 2010 C# Windows Forms Application everything in Form1.Designer.cs  was created automatically exept thie code that I added to Quit Inventor when the Dispose method is called. The dispose method is always called when the form is shut down. This seems like a good place to call the Quit method on the Inventor Application object. (Just to be clear, the Dispose method is not part of the Inventor API).  The Quit method on the Inventor Application object is what removes Inventor from memory.