I actually import the iphlpapi.dll to use SendARP from Windows C Library, but I can't control how many request it sends.
ARP is in Network Layer, so it should be done thanks to Raw Sockets, but I don't find anything useful bout Raw Sockets in C#.
Edit : I already know Pcap.NET but I forget it was open-source, I'll try to find a solution in his source code (I prefer to developp my own tools from scratch) I'll post what I'll find something.