PluginInterface

using System;
using System.IO;
using System.Reflection;

namespace GenericPluginMasterInterfaceNamespace
{
    public class GenericPluginServices
    {
        private Types.AvailablePlugins colAvailablePlugins = new Types.AvailablePlugins();

        /// <summary>
        /// A Collection of all Plugins Found and Loaded by the FindPlugins() Method
        /// </summary>
        public Types.AvailablePlugins AvailablePlugins
        {
            get { return colAvailablePlugins; }
            set { colAvailablePlugins = value; }
        }

        /// <summary>
        /// Searches the Application's Startup Directory for Plugins
        /// </summary>
        public void FindPlugins(Boolean clearFirst, LoggingUtilities.Source source)
        {
            FindPlugins(AppDomain.CurrentDomain.BaseDirectory, clearFirst, source);
        }
        /// <summary>
        /// Searches the passed Path for Plugins
        /// </summary>
        /// <param name="Path">Directory to search for Plugins in</param>
        public void FindPlugins(string Path, Boolean clearFirst, LoggingUtilities.Source source)
        {
            //First empty the collection, we're reloading them all
            if (clearFirst)
                colAvailablePlugins.Clear();

            //Go through all the files in the plugin directory
            foreach (String fileOn in Directory.GetFiles(Path))
            {
                FileInfo file = new FileInfo(fileOn);

                //Preliminary check, must be .dll
                if (file.Extension.Equals(".dll"))
                {
                    //Add the 'plugin'
                    this.AddPlugin(fileOn, source);
                }
            }
        }

        /// <summary>
        /// Unloads and Closes all AvailablePlugins
        /// </summary>
        public void ClosePlugins()
        {
            foreach (Types.AvailablePlugin pluginOn in colAvailablePlugins)
            {
                //Close all plugin instances
                //We call the plugins Dispose sub first incase it has to do
                //Its own cleanup stuff
                //pluginOn.Instance.Dispose();

                //After we give the plugin a chance to tidy up, get rid of it
                pluginOn.Instance = null;
            }

            //Finally, clear our collection of available plugins
            colAvailablePlugins.Clear();
        }

        private void AddPlugin(string FileName, LoggingUtilities.Source source)
        {
            //Create a new assembly from the plugin file we're adding..
            Assembly pluginAssembly = Assembly.LoadFrom(FileName);

            try
            {

                //Next we'll loop through all the Types found in the assembly
                foreach (Type pluginType in pluginAssembly.GetTypes())
                {
                    if (pluginType.IsPublic) //Only look at public types
                    {
                        if (!pluginType.IsAbstract)  //Only look at non-abstract types
                        {
                            //Gets a type object of the interface we need the plugins to match
                            Type typeInterface = pluginType.GetInterface("GenericPluginMasterInterfaceNamespace.IGenericPluginMasterInterface", true);

                            //Make sure the interface we want to use actually exists
                            if (typeInterface != null)
                            {
                                //Create a new available plugin since the type implements the IPlugin interface
                                Types.AvailablePlugin newPlugin = new Types.AvailablePlugin();

                                //Set the filename where we found it
                                newPlugin.AssemblyPath = FileName;

                                //Create a new instance and store the instance in the collection for later use
                                //We could change this later on to not load an instance.. we have 2 options
                                //1- Make one instance, and use it whenever we need it.. it's always there
                                //2- Don't make an instance, and instead make an instance whenever we use it, then close it
                                //For now we'll just make an instance of all the plugins
                                newPlugin.Instance = (IGenericPluginMasterInterface)Activator.CreateInstance(pluginAssembly.GetType(pluginType.ToString()));

                                //Add the new plugin to our collection here
                                this.colAvailablePlugins.Add(newPlugin);

                                //cleanup a bit
                                newPlugin = null;
                            }

                            typeInterface = null; //Mr. Clean
                        }
                    }
                }
            }
            catch (ReflectionTypeLoadException ex1)
            {
                for (int a = 0; a < ex1.LoaderExceptions.Length; a++)
                {
                    LoggingUtilities.LogFunctions.Log("", source, LoggingUtilities.MessageType.Error, ex1.LoaderExceptions[a]);
                }

                Console.WriteLine(ex1.Message);
            }
            catch (Exception ex2)
            {
                LoggingUtilities.LogFunctions.Log("", source, LoggingUtilities.MessageType.Error, ex2);
                Console.WriteLine(ex2.Message);
            }

            pluginAssembly = null; //more cleanup
        }
    }

    namespace Types
    {
        /// <summary>
        /// Collection for AvailablePlugin Type
        /// </summary>
        public class AvailablePlugins : System.Collections.CollectionBase
        {
            //A Simple Home-brew class to hold some info about our Available Plugins

            /// <summary>
            /// Add a Plugin to the collection of Available plugins
            /// </summary>
            /// <param name="pluginToAdd">The Plugin to Add</param>
            public void Add(Types.AvailablePlugin pluginToAdd)
            {
                this.List.Add(pluginToAdd);
            }

            /// <summary>
            /// Remove a Plugin to the collection of Available plugins
            /// </summary>
            /// <param name="pluginToRemove">The Plugin to Remove</param>
            public void Remove(Types.AvailablePlugin pluginToRemove)
            {
                this.List.Remove(pluginToRemove);
            }

            /// <summary>
            /// Finds a plugin in the available Plugins
            /// </summary>
            /// <param name="pluginNameOrPath">The name or File path of the plugin to find</param>
            /// <returns>Available Plugin, or null if the plugin is not found</returns>
            public Types.AvailablePlugin Find(string pluginNameOrPath)
            {
                Types.AvailablePlugin toReturn = null;

                //Loop through all the plugins
                foreach (Types.AvailablePlugin pluginOn in this.List)
                {
                    //Find the one with the matching name or filename
                    if (pluginOn.AssemblyPath.Equals(pluginNameOrPath) ||
                        String.Compare(pluginOn.Instance.returnName(), pluginNameOrPath) == 0)
                    {
                        toReturn = pluginOn;
                        break;
                    }
                }
                return toReturn;
            }

            public Types.AvailablePlugin Get(int index)
            {
                if (index > this.List.Count)
                {
                    return null;
                }
                else
                {
                    return (Types.AvailablePlugin)this.List[index];
                }
            }
        }

        /// <summary>
        /// Data Class for Available Plugin.  Holds and instance of the loaded Plugin, as well as the Plugin's Assembly Path
        /// </summary>
        public class AvailablePlugin
        {
            //This is the actual AvailablePlugin object..
            //Holds an instance of the plugin to access
            //ALso holds assembly path... not really necessary
            private IGenericPluginMasterInterface myInstance = null;
            private string myAssemblyPath = "";

            public IGenericPluginMasterInterface Instance
            {
                get { return myInstance; }
                set { myInstance = value; }
            }
            public string AssemblyPath
            {
                get { return myAssemblyPath; }
                set { myAssemblyPath = value; }
            }
        }
    }
}