Some languages, such as C++, allow you to throw exceptions of any type. Other languages, such as Microsoft C# and Visual Basic, require that every thrown exception be derived from the Exception class. To maintain compatibility between languages, the common language runtime (CLR) wraps objects that do not derive from Exception in a System.Runtime.CompilerServices.RuntimeWrappedException object.

You can use the System.Runtime.CompilerServices.RuntimeCompatibilityAttribute class to specify whether exceptions should appear wrapped inside catch blocks and exception filters for an assembly. Many language compilers, including the Microsoft C# and Visual Basic compilers, apply this attribute by default to specify the wrapping behavior.

Note that the runtime still wraps exceptions even if you use the System.Runtime.CompilerServices.RuntimeCompatibilityAttribute class to specify that you do not want them wrapped. In this case, exceptions are unwrapped only inside catch blocks or exception filters.