For most new projects we recommend using the declarations for .NET, available to download as source. These are usable with Framework 4 and also current .NET Core releases such as .NET 5. To use the .NET declarations you will need the NAG Library installed on your computer.
.NET includes classes that provide declarations that allow managed .NET code to access functions from a native compiled library such as the NAG Library.
The declarations are provided in C# and VB.NET syntax in several formats eg `flcsdnet64.cs` which are the C# declarations for 64bit Windows, using 32bit integers.
NAG .NET Library
For the older Windows .NET Framework 4, NAG supplies the NAG .NET Library. This is supplied as a compiled library with around 500 methods based on Mark 24 of the NAG Library, fully documented with examples for each case.