VSCode: error TS5042: Option ‘project’ cannot be mixed with source files on a command line.

I have been using VSCode a lot lately. I have recently started delving into TypeScript and wanted to use VSCode to begin developing my first project. I was following a tutorial on Lynda.com and for the life of me could not get it to “transpile” my TS project. I setup everything according to this site and it failed. What I kept getting was this error:

error TS5042: Option ‘project’ cannot be mixed with source files on a command line.

This error is all over the web and not a single solution helped. I am guessing it is caused by the fact I have VS2015, VS2017, and VSCode installed on my box. But, this is the weird thing, if I go to the PowerShell in the Terminal window and paste the EXACT command that VSCode uses… IT WORKS!!! What? I started puling my hair out at this point…

Ok, now that really sucked. So, I got fed up and just build my own tasks.json using the “Other” option and here is what I entered:

[code language=”javascript”]
    // See https://go.microsoft.com/fwlink/?LinkId=733558
    // for the documentation about the tasks.json format
    "version": "2.0.0",
    "tasks": [
            "taskName": "DaveCra TSC Task for VSCode",
            "command": "tsc -p tsconfig.json",
            "type": "shell",
            "problemMatcher": [
            "group": {
                "kind": "build",
                "isDefault": true

Once I set this up, it was the default build task and a CTRL+SHIFT+B ran fine. Right after that I was able to go to the PowerShell terminal and type “node ” and it ran like a charm. wlEmoticon-hotsmile.png


If you have been doing much work in VSTO and especially around Excel and embeddings, you may have been bit by this bug. Does this error look familiar:


“The program used to create this object is Excel. That program is either not installed on your computer or it is not responding. To edit this object, install Excel or ensure that any dialog boxes in Excel are closed.”

This error can be caused by the following:

  • A .NET3.5 Add-in or a .NET 4.0 Add-in
  • You have attached to the WorkbookOpen and/or WorkbookActivate events.
  • You are trying to edit/open/double-click on an embedded Excel instance inside a Word or PowerPoint document.

There have been several reports of this problem on the Microsoft MSDN site:

There are also a number of KB articles that document the problem and attribute it to specific programs:

The problem is specifically documented here:

Simple Solution

The basic simple answer is to place a Marshal.ComReleaseObject(Wb) at the end (or better, in the Finally block) of your event handlers. This will properly allow Word and excel to handle the OLE communication by not having VSTO hang on to an instance handle of the workbook, therefore causing the error.

And this is not carte blanche to start placing ComReleaseObject() all over your code. I have found VERY VERY few limited cases where using ComReleaseObject() in an add-in necessary. And this is one of them. Hot smile

Orphan Issue

It is not a panacea, either. Confused smile While it resolves the issues of OLE initialization and allows you to edit your Excel embedding in Word (as one example), it does not prevent one other scenario that I like to call “Orphaned Excel.” In this scenario, you edit your embedded Excel instance in another Window (usually via a right-click / Ole Object / Open). If you leave Excel open, return to Word and close the document, Excel should close. But in the VSTO COM/OLE scenario it may not – it will remain open with the embedded workbook still editable. However, it is orphaned an no longer associated with its container. Any edits will be lost.

That is where a solution I created for Excel/Word OLE interaction comes in here:

This add-in is very well commented and explains the following:

  • When a workbook is opened, it looks to see if it is embedded.
  • If it is, it connects to the running instance of Word, and gets a reference to the parent document.
  • A timer in the add-in will then continually check the status of the document
  • If the parent document is still opened, nothing happens. However, if Word is existed or the parent document is closed, the child embedding is forced closed.


However, and this is important note. For everything you do, you are in the sandbox with other kids. Sad smile Your add-in is loading in the same AppDomain as everybody else. If there is another VSTO 3.5/4.0 Add-in loaded in Excel and that add-in is not doing any of the above – well, your still going to have problems.

That is what makes this issue so vexing. Steaming mad You can play by all the rules, but you cannot prevent other kids from throwing sand. This is why I see some customers going to the extreme to manage out (disable) all other COM add-ins when they load their solution. But this does not work for HKEY_LOCAL_MACHINE Loaded add-ins.

There are few options and most involve a lot of code. I say, TEST. If your are in an Enterprise environment, test all your VSTO add-ins together, find code owners and get everyone on the same page. If it is a vendor add-in causing the problem, point them here. Smile