In .NET the Common Language Runtime (CLR) virtual machine manages the program execution. Code that is written in a .NET language is hence called Managed Code, while code like C and C++ that compiles to native programs that doesn't require CLR is referred to as Unmanaged Code. It turns out that many types can not be shared straight up between managed code and unmanaged code. To do this the types needs to be converted. This conversion process is called marshaling . I got some real hands on experience with marshaling the last week when I worked on moving and re-writing C++ code to C#. One of the structs (that included an array of another type of struct, that in turn included another struct...) in the C++ code is written to disk with exact requirements on the number of bytes the data is allowed to occupy. My first naive approach was to simply replicate the structs in C# and, using a BinaryFormatter and a MemoryStream, convert them to a byte array. This approach worked very well ...