 | This article may be too technical for most readers to understand. (March 2015) |
Platform Invocation Services, commonly referred to as P/Invoke, is a feature of Common Language Infrastructure implementations, like Microsoft's Common Language Runtime, that enables managed code to call native code.
Managed code, such as C# or VB.NET, provides native access to classes, methods, and types defined within the libraries that make up the .NET Framework. While the .NET Framework provides an extensive set of functionality, it may lack access to many lower level operating system libraries normally written in unmanaged code or third party libraries also written in unmanaged code. P/Invoke is the technique a programmer can use to access functions in these libraries. Calls to functions within these libraries occur by declaring the signature of the unmanaged function within managed code, which serves as the actual function that can be called like any other managed method. The declaration references the library's file path and defines the function parameters and return in managed types that are most likely to be implicitly marshaled to and from the unmanaged types by the common language run-time (CLR). When the unmanaged data types become too complex for a simple implicit conversion from and to managed types, the framework allows the user to define attributes on the function, return, and/or the parameters to explicitly refine how the data should be marshaled so as not to lead to exceptions in trying to do so implicitly.
There are many abstractions of lower-level programming concepts available to managed code programmers as compared to programming in unmanaged languages. As a result, a programmer with only managed code experience will need to brush up on programming concepts such as pointers, structures, and passing by reference to overcome some of the obstacles in using P/Invoke.