transientassembly

Transient assembly refers to a compiled code library that exists only in memory during program execution, rather than as a persisted file on disk. In managed runtimes like .NET, such assemblies are created at runtime by dynamic compilation techniques (Reflection.Emit, CodeDOM, Roslyn) to execute code supplied by a script or generated on the fly. They differ from ordinary assemblies (DLLs or EXEs) that are built, stored, and loaded from disk.

Transient assemblies are typically loaded into a separate isolation context (an AssemblyLoadContext in .NET Core or an AppDomain in earlier frameworks) to allow unloading or reloading without restarting the process. Because they are not saved, they usually lack a stable file path or version, though they can carry in-memory metadata and optional debugging symbols.

Common use cases include interactive scripting environments, template engines that emit executable code, unit-test runtimes, and sandboxed execution of dynamic or untrusted code. They enable dynamic behavior without altering the host application's on-disk footprint, but they introduce challenges in dependency resolution, security, isolation, and memory management. In practice, transient assemblies are considered temporary runtime artifacts, with lifecycles tied to the hosting process or to the scope of the dynamic operation that produced them.