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copied!<p>Normally the framework loads the assemblies on-demand. A different approach would be to use a dynamic load pattern or composite pattern. Starting from the framework 4.0, MS introduced the <a href="http://msdn.microsoft.com/en-us/library/bb384200(v=vs.110).aspx" rel="nofollow">System.Addin</a> namespace to help programmers in this. I have the following class which I use in my projects to achieve the same with Framework 2.0 compatibility:</p> <pre><code>using System; using System.Collections.Generic; using System.Diagnostics; using System.Globalization; using System.IO; using System.Reflection; namespace MyNamespace { [Serializable] public enum CompositeLoaderFilter { ImplementsInterface = 0, InheritsBaseClass = 1 } [Serializable] public static class Composite { private static readonly CompositeManager manager = new CompositeManager(); public static CompositeManager Manager { get { return manager; } } } [Serializable] public class CompositeManager : MarshalByRefObject { private SortedList<string, Type> m_addIns; public int GetInMemoryComponents(Type addInType, CompositeLoaderFilter filter) { m_addIns = internal_GetInMemoryServices(addInType, filter); return m_addIns.Count; } public int GetComponents(Type addInType, CompositeLoaderFilter filter) { string addInPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location); return GetComponents(addInPath, "*.dll", SearchOption.TopDirectoryOnly, addInType, filter); } public int GetComponents(string addInSearchPattern, Type addInType, CompositeLoaderFilter filter) { string addInPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location); return GetComponents(addInPath, addInSearchPattern, SearchOption.TopDirectoryOnly, addInType, filter); } public int GetComponents(string addInPath, string addInSearchPattern, Type addInType, CompositeLoaderFilter filter) { return GetComponents(addInPath, addInSearchPattern, SearchOption.TopDirectoryOnly, addInType, filter); } public int GetComponents(string addInPath, string addInSearchPattern, SearchOption addInSearchOption, Type addInType, CompositeLoaderFilter filter) { AppDomainSetup setup = AppDomain.CurrentDomain.SetupInformation; setup.PrivateBinPath = addInPath; setup.ShadowCopyFiles = "false"; AppDomain m_appDomain = AppDomain.CreateDomain("MyNamespace.CompositeManager", null, setup); CompositeManager m_remoteLoader = (CompositeManager)m_appDomain.CreateInstanceFromAndUnwrap(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "MyAssembly.dll"), "MyNamespace.CompositeManager"); m_addIns = m_remoteLoader.RemoteGetServices(addInPath, addInSearchPattern, addInSearchOption, addInType, filter); #if DEBUG DebugLoadedAssemblies(); #endif AppDomain.Unload(m_appDomain); return m_addIns.Count; } public object CreateInstance(string typeName) { if (!m_addIns.ContainsKey(typeName)) throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "Type {0} was not loaded..", typeName), "typeName"); MethodInfo method = m_addIns[typeName].GetMethod("GetInstance", BindingFlags.Static | BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy); if (method != null) return method.Invoke(m_addIns[typeName], null); else return Activator.CreateInstance(m_addIns[typeName]); } public object CreateInstance(Type type) { if (type == null) throw new ArgumentNullException("type", "Type is null"); if (!m_addIns.ContainsKey(type.FullName)) throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "Type {0} was not loaded..", type.FullName), "type"); MethodInfo method = type.GetMethod("GetInstance", BindingFlags.Static | BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy); if (method != null) return method.Invoke(type, null); else return Activator.CreateInstance(type); } public T CreateInstance<T>() { if (!m_addIns.ContainsKey(typeof(T).FullName)) throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "Type {0} was not loaded..", typeof(T).FullName), "T"); MethodInfo method = typeof(T).GetMethod("GetInstance", BindingFlags.Static | BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy); if (method != null) return (T)method.Invoke(typeof(T), null); else return Activator.CreateInstance<T>(); } public IEnumerable<Type> AvailableServices { get { foreach (KeyValuePair<string, Type> item in m_addIns) { yield return item.Value; } } } public Type[] AvailableTypes { get { List<Type> list = new List<Type>(); foreach (KeyValuePair<string, Type> item in m_addIns) list.Add(item.Value); return list.ToArray(); } } public T[] GetObjects<T>() { List<T> list = new List<T>(); foreach (KeyValuePair<string, Type> item in m_addIns) list.Add((T)CreateInstance(item.Value)); return list.ToArray(); } public object[] AvailableObjects { get { List<object> list = new List<object>(); foreach (KeyValuePair<string, Type> item in m_addIns) list.Add(CreateInstance(item.Value)); return list.ToArray(); } } internal SortedList<string, Type> internal_GetInMemoryServices(Type addInType, CompositeLoaderFilter filter) { SortedList<string, Type> validAddIns = new SortedList<string, Type>(); Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies(); foreach (Assembly assembly in assemblies) { try { Type[] types = assembly.GetTypes(); foreach (Type type in types) { switch (filter) { case CompositeLoaderFilter.ImplementsInterface: if (type.GetInterface(addInType.Name) != null) validAddIns.Add(type.FullName, type); break; case CompositeLoaderFilter.InheritsBaseClass: if (type.BaseType == addInType) validAddIns.Add(type.FullName, type); break; } } } catch (FileLoadException flex) { Debug.WriteLine(string.Format(CultureInfo.CurrentCulture, "{0} MyNamespace.CompositeManager: {1}", DateTime.Now.ToString(), flex.Message)); } catch (Exception ex) { Debug.WriteLine(string.Format(CultureInfo.CurrentCulture, "{0} MyNamespace.CompositeManager: {1}", DateTime.Now.ToString(), ex.Message)); } } return validAddIns; } internal SortedList<string, Type> RemoteGetServices(string addInPath, string addInSearchPattern, SearchOption addInSearchOption, Type addInType, CompositeLoaderFilter filter) { string[] files = Directory.GetFiles(addInPath, addInSearchPattern, addInSearchOption); SortedList<string, Type> validAddIns = new SortedList<string, Type>(); if (files.Length > 0) { foreach (string file in files) { if (String.CompareOrdinal(addInPath, file) != 0) { try { Assembly assembly = Assembly.LoadFrom(file); Type[] types = assembly.GetTypes(); foreach (Type type in types) { switch (filter) { case CompositeLoaderFilter.ImplementsInterface: if (type.GetInterface(addInType.Name) != null) validAddIns.Add(type.FullName, type); break; case CompositeLoaderFilter.InheritsBaseClass: if (type.BaseType == addInType) validAddIns.Add(type.FullName, type); break; } } } catch (FileLoadException flex) { Debug.WriteLine(string.Format(CultureInfo.CurrentCulture, "{0} MyNamespace.CompositeManager: {1}", DateTime.Now.ToString(), flex.Message)); } catch (Exception ex) { Debug.WriteLine(string.Format(CultureInfo.CurrentCulture, "{0} MyNamespace.CompositeManager: {1}", DateTime.Now.ToString(), ex.Message)); } } } } #if DEBUG DebugLoadedAssemblies(); #endif return validAddIns; } #if DEBUG internal void DebugLoadedAssemblies() { foreach (Assembly a in AppDomain.CurrentDomain.GetAssemblies()) { //Debug.WriteLine(string.Format("Domain: {0} Assembly: {1}", AppDomain.CurrentDomain.FriendlyName, a.FullName)); } } #endif } } </code></pre> <p>Following a sample usage:</p> <pre><code>Composite.Manager.GetComponents(typeof(IMyService), CompositeLoaderFilter.ImplementsInterface); IMyService[] services = Composite.Manager.GetObjects<IMyService>(); </code></pre> <p>The class will load all the assemblies in current folder, inspecting them to see if they contains a Type that match the input parameters. Because is impossible to unload an assembly once loaded, the class will load them inside a different AppDomain, which in contrary to single assemblies, can be dropped.</p> <p>In order to use it in your project you should proceed as following:</p> <ul> <li>Remove the (hard) reference to your assembly</li> <li>Implement an interface to communicate with your class</li> <li>Load the types that implements the above interface</li> <li>Use your class through the interface</li> </ul> <p>Hope it helps :)</p>

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