Atdl4net - FIXatdl for .NET
Atdl4net is a commercially supported open source implementation of FIXatdl, the FIX Protocol Algorithmic Trading Definition Language standard developed by FIX Protocol Limited (FPL).
Atdl4net is developed in C# and now is supported on .NET 4.6.2.
The original project and more details could be found here.