LabVIEW Error 1386: The Specified .NET Class is Not Available in LabVIEW

Updated Apr 23, 2019

Reported In


  • LabVIEW
  • TestStand

Operating System

  • Windows

Issue Details

​I have a LabVIEW VI, DLL, or I downloaded the exercises and solutions for the "Developing Test Programs Using TestStand" but when I run my VI I get:
Error 1386:
The specified .NET class is not available in LabVIEW.



Starting with Windows 7 and later, Windows can block access to an Assembly.

To resolve this, right-click the assembly and click Unblock on the General tab to grant an assembly full trust.

If the above step does not work, follow the steps below to allow LabVIEW access to all .NET assemblies. Please note that this approach imposes a potential security risk.

  1. Use a text editor to create a file that contains the following text: 
    <?xml version ="1.0"?>
        <loadFromRemoteSources enabled="true" />

  2. Save this file as LabVIEW.exe.config to trust all assemblies loaded into LabVIEW.
  3. Place the file created in the previous step in the same directory as the file it was created for: E.g. a LabVIEW.exe.config file in the same directory as the LabVIEW.exe file, which is typically located in C:\Program Files (x86)\National Instruments\LabVIEW 2018\.

Additional Information

  • Please note: This error message may also occur when you attempt to load a 64-bit .NET DLL into a 32-bit version of LabVIEW or vice-versa.
  • Pleas see Configuring a .NET Client Application - LabVIEW 2018 Help  for more information on how to apply configuration files to LabVIEW Project files, shared libraries, or stand-alone executables.


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