// here you could loop through a directory and try every file...
Assembly[] assemblies = new Assembly[1];
try
{
	assemblies[0] = Assembly.LoadFrom(@"C:\firstPlugin.dll");
}
catch { }
try
{
	assemblies[1] = Assembly.LoadFrom(@"C:\secondPlugin.dll");
}
catch { }

// search each loaded assembly for the type
foreach (Assembly assembly in assemblies)
{
	foreach (Type type in assembly.GetTypes())
	{
		if (type.IsClass)
		{
			// try to create an intance of it - maybe not the 
			// safest method but works
			try
			{
			    object o = Activator.CreateInstance(type);

			    // IPlugin is a custom interface we made
				if (o is IPlugin)
				{
				    IPlugin plugin = (IPlugin)o;
				    plugin.Execute();
				}
			}
			catch
			{
				
			}
		}
	}
}