AutoCAD crashes when starting from Revit API

[Anonymous]

I have a simple Revit addin setup where the users selects a linked dwg and the addins opens tha dwg in autocad to edit. However whenever I start AutoCAD from within the Revit addin I get the error "Unhandled Exception C0000005 (Access Violation Reading 0x0008) at address CADE4A58h".

Even this simple code gives me the error:

using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.Attributes;

namespace ClassLibrary1
{
    [TransactionAttribute(TransactionMode.Manual), RegenerationAttribute(RegenerationOption.Manual)]
    public class Class1 : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            System.Diagnostics.Process.Start(@"C:\test.dwg");
         
            return Result.Succeeded;
        }
    }
}

Just to be clear. If I double click the DWG file in windows explorer the file opens just fine without error. If I create a console application outside of the Revit API with just the process start command, the DWG opens just fine. IE

using System;
using System.Diagnostics;

namespace startautocad
{
    class Program
    {
        static void Main(string[] args)
        {
            Process.Start(@"C:\test.dwg");
        }
    }
}

Any idea why I get the error in the Revit addin?

[jeremytammik]

Dear Mwilson1,

Thank you for the interesting question.

No idea whatsoever.

However, you could try an alternative approach:

Use the AutoCAD COM Interop functionality to start up AutoCAD, load the DWG, and either display or hide the user interface, as you prefer:

http://thebuildingcoder.typepad.com/blog/2013/04/launching-autocad-within-a-revit-add-in.html

I hope this helps.

Cheers,

Jeremy

[stever66]

I really don't have a clue, but lots of possibilities come to mind:

windows associtivity, autocad license, autocad startup arguments, user logon, network issue.

Unless you have already tried this, why not try substituting a more basic program instead of autocad and see if that works.  Like opening a simple text document. 

Also, you might try some of the overloads for this command, listed here:

https://msdn.microsoft.com/en-us/library/system.diagnostics.process.start(v=vs.110).aspx

For example, you might try specifying the name of the program to run.

[Anonymous]

Thank you for the suggestion. I was able to run

Process.Start(@"c:\test.txt");
Process.Start(@"c:\test.pdf");

Successfully. The text file opened in notepad and the pdf in Bluebeam.

I don't know if it helps, but when I open a DWG with the code above, I'm able to work in the drawing for a second or two. Usually just enough to zoom around, before it crashes. However if I do nothing it still crashes.

Also as a note, when I open a DWG in AutoCAD with the Visual Studio debugger running on the Revit addin, AutoCAD crashes completly without an error message. It's only if I run outside of visual studio do I get the error above.

I'm trying to make this addin as generic as possible for the office, because we have all different flavors of AutoCAD installed, between 2010 and 2016. 

[stever66]

For what its worth, I can put:

System.Diagnostics.Process.Start(@"C:\test.dwg");

in a Sharp Develop Macro (inside Revit), and it starts autocad and opens the file just fine.   It takes it longer than if I just click the Autocad icon itself, but it does the same thing if I just double click a file in explorer. 

Jeremy's suggestion might be your best bet.