TestStand installs .NET interop assemblies for the TestStand API in the <TestStand>\API\DotNet\Assemblies directory and in the Global Assembly Cache (GAC). The interop assemblies support the current and earlier versions of the TestStand API, as shown in the following table.

TestStand API Version .NET Version
TestStand 2025 Q2 and later .NET 8 (CLR 5.0 or later)
TestStand 2024 Q4 For .NET Adapter .NET 8 (CLR 5.0 or later)
For user interfaces .NET Framework CLR 4.0
TestStand 2012 — TestStand 2023 Q4 .NET Framework CLR 4.0
TestStand 4.0 — TestStand 2010 SP1 .NET Framework CLR 2.0
TestStand 3.5 or earlier .NET Framework CLR 1.1