Can not load SlpClient because of dll exception C# SLP

I try to use the slp-sharp.dll and have the following code:

var slp = new SlpClient(String.Empty);
Console.WriteLine("SLP Opened");

slp.Find("inbtest:inb.http", new string[0],
  delegate (string url, UInt16 lifetime)
  {
  // found a service
  Console.WriteLine("found {0}, lifetime = {1}", url, lifetime);
  });
Console.WriteLine("SLP Closed");

I always get an exception in the following line:

var slp = new SlpClient(String.Empty);

The DLL "slp": The specified module was not found. (Exception of HRESULT: 0x8007007E) cannot be loaded.

The slp-sharp.dll is already in the build folder and as referance set too.

Anyone with experience with slp-sharp.dll?