Managed code is code that is written to target the services of the Common Language Runtime. In order to target these services, the code must provide a minimum level of information (metadata) to the runtime. All C#, Visual Basic .NET, and JScript .NET code is managed by default.

Visual Studio .NET C++ code is not managed by default, but the compiler can produce managed code by specifying a command-line switch (/CLR). Closely related to managed code is managed data--data that is allocated and de- allocated by the Common Language Runtime's garbage collector. C#, Visual Basic, and JScript .NET data is managed by default. C# data can, however, be marked as unmanaged through the use of special keywords.
Visual Studio .NET C++ data is unmanaged by default (even when using the /CLR switch), but when using Managed Extensions for C++, a class can be marked as managed using the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector.

In addition, the class becomes a full participating member of the .NET Framework community, with the benefits and restrictions that it brings. An example of a benefit is proper interoperability with classes written in other languages (for example, a managed C++ class can inherit from a Visual Basic class).

An example of a restriction is that a managed class can only inherit from one base class.