public interface IParadigmPlugin
    {
        /// <summary>
        /// Activates the plugin, showing it's main form
        /// </summary>
        void ActivatePlugin();
    }

    /// <summary>
    /// This class defines the custom attribute for plugin display names
    /// </summary>
    [AttributeUsage(AttributeTargets.Class)]
    public class ParadigmPluginDisplayNameAttribute : System.Attribute
    {
        private string displayName;
 
        public ParadigmPluginDisplayNameAttribute(string displayName)
            : base()
        {
            this.displayName = displayName;
        }
 
        public override string ToString()
        {
            return displayName;
        }
    }

    /// <summary>
    /// This class defines the custom attribute for plugin descriptions
    /// </summary>
    [AttributeUsage(AttributeTargets.Class)]
    public class ParadigmPluginDescriptionAttribute : System.Attribute
    {
        private string description;
 
        public ParadigmPluginDescriptionAttribute(string description)
            : base()
        {
            this.description = description;
        }
 
        public override string ToString()
        {
            return description;
        }
    }

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms; // referencing System.Windows.Forms is obviously needed for form usage, make sure to reference it in the project as well
using ParadigmCommon; // you must reference the ParadigmCommon namespace to access the needed attributes and interface
 
namespace TestPlugin
{
    /// <summary>
    /// This is an example of a paradigm plugin
    /// </summary>
    [ParadigmPluginDisplayName("Test Plugin")] // you must provice a display name
    [ParadigmPluginDescription("Test Plugin")] // as well as a description
    public class TestPlugin : IParadigmPlugin  // Your main class must implement the IParadigmPlugin interface
    {
        public void ActivatePlugin() // by implementing the interface, you must implement an ActivatePlugin method
        {
            TestPluginMainForm mainForm = new TestPluginMainForm();
            mainForm.Show();
            mainForm.Activate();
        }
    }
}

    /// <summary>
    /// This class wraps our plugins
    /// </summary>
    public class ParadigmPlugin
    {
        #region Fields
        private IParadigmPlugin plugin;
        private string name;
        private string description;
        #endregion
 
        #region Attributees
        public string Name
        {
            get { return name; }
        }
 
        public string Description
        {
            get { return description; }
        }
        #endregion
 
        /// <summary>
        /// Constructs a plugin wrapper
        /// </summary>
        public ParadigmPlugin(IParadigmPlugin plugin, string name, string description)
        {
            this.plugin = plugin;
            this.name = name;
            this.description = description;
        }
 
        /// <summary>
        /// Activate Plugin
        /// </summary>
        public void Activate()
        {
            plugin.ActivatePlugin();
        }

    class PluginNotValidException : ApplicationException
    {
        public PluginNotValidException(Type type, string param1)
        {
        }
    }

private List<ParadigmPlugin> loadedPlugins = new List<ParadigmPlugin>();

        private void LoadPlugins()
        {
            // search plugin directory for dlls
            string[] files = Directory.GetFiles("Plugins", "*.dll");
 
            // check each file in plugin direction
            foreach (string file in files)
            {
                try
                {
                    // load the assembly and get types
                    Assembly assembly = Assembly.LoadFrom(file);
                    System.Type[] types = assembly.GetTypes();
 
                    // look for our interface in the assembly
                    foreach (System.Type type in types)
                    {
                        // if we found our interface, verify attributes
                        if (type.GetInterface("IParadigmPlugin") != null)
                        {
 
                            if (type.GetCustomAttributes(typeof(ParadigmPluginDisplayNameAttribute), false).Length != 1)
                                throw new PluginNotValidException(type, "Plugin display name is not supported!");
 
                            if (type.GetCustomAttributes(typeof(ParadigmPluginDescriptionAttribute), false).Length != 1)
                                throw new PluginNotValidException(type, "Plugin description is not supported");
 
                            // get custom attributes from plugin
                            string name = type.GetCustomAttributes(typeof(ParadigmPluginDisplayNameAttribute), false)[0].ToString();
                            string description = type.GetCustomAttributes(typeof(ParadigmPluginDescriptionAttribute), false)[0].ToString();
 
                            // create the plugin using reflection
                            Object o = Activator.CreateInstance(type);
 
                            ParadigmPlugin plugin = new ParadigmPlugin(o as IParadigmPlugin, name, description);                                                               
 
                            loadedPlugins.Add(plugin);
                        }
                    }
                }
                catch (Exception e)
                {
                    MessageBox.Show(e.Message, "Plugin Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
 
            // iterate through list and add them to our form control
            for (int i = 0; i < loadedPlugins.Count; i++)
            {
                ParadigmPlugin plugin = loadedPlugins[i];
 
                pluginsToolStripMenuItem.DropDownItems.Add(plugin.Name);
                pluginsToolStripMenuItem.DropDownItems[i].Click += delegate { plugin.Activate(); };
                pluginsToolStripMenuItem.DropDownItems[i].Text = plugin.Name;
                pluginsToolStripMenuItem.DropDownItems[i].ToolTipText = plugin.Description;
            }
        }