A simple plug-in engine using Reflection

using System;
using System.IO;
using System.Net;
using System.Reflection;
using System.Security;
using System.Security.Permissions;

namespace PluginDemo
{
    internal class Program
    {
        // Directory that contains plugins files
        private const string pluginDir = "Plugins";

        // Plugins files extension mask
        private const string pluginExtMask = "*.dll";

        static void Main(string[] args)
        {
            Console.WriteLine("1. Old way of running the plugins - full trust:\r\n");
            var pluginMan = new PluginBase.PluginManager();
            RunPlugins(pluginMan);

            Console.WriteLine(Environment.NewLine);

            Console.WriteLine("2. New way of running the plugins - limited trust:\r\n");
            var pset = new PermissionSet(PermissionState.None); /* deny all */
            /* uncomment the next line to allow file operations for all the plugins  */
            // pset.AddPermission(new FileIOPermission(FileIOPermissionAccess.Read | FileIOPermissionAccess.Write, Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)));
            /* uncomment the next line to allow working of the WebDownloadPlugin */
            // pset.AddPermission(new WebPermission(PermissionState.Unrestricted));
            pluginMan = PluginBase.PluginManager.GetInstance(pset);
            RunPlugins(pluginMan);

            Console.ReadKey();
        }

        static void RunPlugins(PluginBase.PluginManager pluginMan)
        {
            var path = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), pluginDir);

            foreach (var f in new DirectoryInfo(path).GetFiles(pluginExtMask))
            {
                var plugin = pluginMan.LoadPlugin(Path.Combine(path, f.Name));
                try
                {
                    plugin.Run();
                    Console.WriteLine("Plugin {0} has finished work\r\n", plugin.Name);
                }
                catch (Exception ex)
                {
                    Console.WriteLine("An exception occurred in the {0} plugin: {1}\r\n", plugin.Name, ex.Message);
                }
            }
        }
    }
}