Error "Object reference not set to an instance of an object", when invoking a workflow


I am getting this error when invoking a workflow as following:


And these are the arguments I am calling the workflow with:


Thanks for any help you might be able to provide with.

It looks like either WIList or Config is not yet initialized. Make sure that you are assigning them a value before attempting to use them.

@DanielMitchell WIList is a DataTable obtained in a previous invocation and it has records on it. Config is a Dictionary which is also used successfully in previous invocations during the process.

Is there anything else I might need to look into?


Try to print some of their values right before the Invoke that’s throwing an error, just to double check. You’re getting an “Object reference not set to an instance of an object” exception and those are the only two objects being used in that activity.

@DanielMitchell it is weird. It seems to be Config; but I am using the same argument in another previous invocation successfully, as following. Would you think on any reason about this behavior .



Not off the top of my head. If you want to zip your solution and put it up here or send it my way I can take a look at it for you.

Here you go,

Thanks! (95.0 KB)

So it looks like the “Invoke Navigate to Work Item Details” activity is what’s actually throwing the exception, I didn’t see that in your first post. So the problem isn’t with your arguments in Main, it’s with the arguments that you’re actually passing to that specific workflow.

However, I’m not seeing anything immediately wrong with that part of the workflow. I can’t run it, since a lot of the directory values are hard-coded for your PC, but there wasn’t anything that screamed wrong. I did have to delete the project.json file and let Studio recreate it so maybe try that.

Yes, the error is there; but as the argument is coming from Main, that is why I posted that.

I deleted it; but getting same error.

I noticed that Config becomes “null” when it goes into the “For Each Row” activity within “Invoke Navigate to Work Item Details”; before, at sequence level, the value was still there.

That means make sure Config is available to the workflow from where you are invoking this workflow which is throwing error.

Pretty frustrating this error can become. Doubly make sure you are passing/importing the arguments in each workflow that is being invoked. Also check the values in config.