Jump to content

File that one under "Exotic bug" - The Vestigial .NET Constructor Terminal (47sec video)

Recommended Posts

This took a decent amount of debugging and headscratching to figure out why a particular .NET call kept failing.

I inadvertently discovered and wired a "vestigial" output terminal that exists on .NET Constructor Nodes in LabVIEW 2012. Interestingly, this output terminal returns the same datatype as the "real" output terminal, yet does not return a valid ref.

Pretty sure this is a CAR-able bug, but just documenting behavior here just in case someone else runs into this. (Can you think of possibilities to exploit this as a feature??)

Here's a 47sec YouTube video with no sound; Vestigial Terminal at 25sec:

...and for the sake of organic search: Error 1172 - "LabVIEW: A .NET exception occurred in an external assembly. For information about correcting this error, copy the following exception (in bold), and search the Microsoft Developer Network (MSDN) Web site or the Web for a possible explanation."

And in case the resolution for this "error" and my "bug" was not clear: I just had to rewire the terminal to the "correct" output. Further, my choice of .NET assembly, constructor and property for the demonstration was arbitrary; this appears to affect all .NET Constructor Nodes.

  • Like 2
Link to comment

Did you find this in code you loaded from a previous version of LabVIEW, by chance?

Nope; this does not appear to be an upgrade mutation bug. Brand new install of LV2012, brand new code. I just accidentally stumbled upon it coding with sausage fingers. You can drop a .NET constructor and check yourself; I'm curious if it exists in LV2011 or previous.

Edited by JackDunaway
Link to comment

Yep, reproduced this in LV2011SP1f2, LV2010SP1, and LV2009 (all 32-bit). Guess you're the first lucky guy to find this - and know about it. :thumbup1:

If only this were my first .NET Mugatu Moment recently ... :P

*Mugatu Moment - an internal struggle so confusing and contradictory that, neither absolutely nor ostensibly, one is unable to determine whether one is indeed "taking crazy pills"

Link to comment

The left most one looks like the normal ref terminal...

That's what I thought at first too. However, the terminal takes up the whole left side of the top of the constructor node (the yellow part). A reference input is normally just the height of a terminal plus a few pixels into the yellow area.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Content

    • By bartek618
      I know how to run .Net executable by MainWindow() constructor but I have some resources defined in App.xaml and MainWindow() doesn't run without them. How to run application starting with App() constructor? Also I need to pass some parameters into MainWindow().
    • By William Hofmeister
      I need to access Aerotech A3200 data with LabView. The Digital Scope in the A3200 software has the capability to record data at 1kHz for 8 seconds in dedicated batches. We use LabView for all functions surrounding the motion control and have the Aerotech LabView package. Using the LabView vis we can only access data a single data point per call and I don't see how to set up a FIFO to Windows LabView. Someone must have looked at this problem lately. Can anyone steer me in the right direction?  Thanks!!
    • By LogMAN
      So this just happened to me and I'm quite confused by it. As it turns out, the .NET Constructor Node not only provides terminals for error in, error out and the reference, but actually two more "hidden" terminals:

      Notice: I left the error terminals untouched and none of the wires are connected (try it yourself). This never occurred to me. Only now, while hunting a null reference exception I found the constructor node looked "off", like this:

      The strange part is that the terminal doesn't actually carry the reference (which is why I receive the null exception). It only specifies the type. The upper left terminal is a void type input, so the wire is always broken.
      Does anyone know why these extra terminals exist? They don't seem to be part of the specification as far as I can tell.
      Any fancy things we can do with this?
    • By ATE-ENGE
      Edit: I'm asking primarily if there is a reason why/when I should/shouldn't use .net functions in my LabVIEW development. The example below is just to demonstrate a case of my question.
      I recently found a custom library that calculates SHA256 hash algorithms However, in this post I see that the same thing can be done with .net 
      My main question is: Is there any reason to build or use a custom library for something where .net functionality already exists? Are there any disadvantages to offloading work to .net ? 
    • By Gribo
      Hello, I am trying to copy multiple cells in LibreOffice, using the UNO API. I encountered an issue in the XCellRangeData object.
      The object's method returns an array of array of any() type. it seems LV can't compile this, even though the wire appears not to be broken. If I try to parse the array of array into a single dimension and then rebuild, the code is broken. See the attached files. Is there a solution for this issue? The alternative would be to copy cells one by one, which is a much slower solution.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.