Gregory< what I have missed
I have

public string GetModInfo(string Assemblyname)
{
string vbTab = " ";
var list = (from m in Assembly.Load(Assemblyname).GetModules() select m.GetTypes().Where(x => x.IsClass)).ToList();
foreach (var className in list) { vbTab = vbTab + className.ToString();
}
return vbTab;
}
call it with like
GetModInfo("System.Windows.Forms") from my class
It tells to me - could not find assemby
More long code with - {var assembly = Assembly.Load(assemblyName) ... works fine
Sure, I have referencies to System.Data.Linq and System.Xml.Linq