For years ASN1C has included a run-time library useable by code written for Microsoft's .NET Framework. In older versions of ASN1C this library was named asn1rt.dll; in newer versions it's named asn1rtcs.dll (cs = csharp). More recent versions of ASN1C have also included a build of this library that targeted Microsoft's .NET Core, a build of the .NET Framework that could run on multiple platforms, not just Windows.

Microsoft's last version of the .NET Framework was .NET Framework v4. After that version they combined .NET Framework, .NET Core, and one or two other specific builds into one build of .NET that can be used in all situations covered by what were previously multiple builds. So starting with ASN1C v7.7 the following builds of asn1rtcs.dll are included:

  1. A build that targets .NET v4 (aka the .NET Framework). This build is still included because there are probably numerous customers who still use it, and because most of the C# samples in the ASN1C SDK are engineered to use it.
  2. A build that targets .NET v5. This build should be useable for any situation where .NET is needed. Note, however, that .NET v5 is officially out of support with Microsoft.
  3. A build that targets .NET v6. As with the .NET v5 build, this build should be useable for any situation where .Net is needed. .Net v6 is supported by Microsoft.

Also note that ASN1C v7.8, which will be released early in 2024, will include a build of the run-time that targets .NET v7.