Assembly 操作

以下是项目中的一个类，用于加载模块DLL及，此类演示了如何在运行文件夹下搜索DLL并通过Assembly类进行加载。

using Core.Dependency;
using Core.Logging;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Web;
using System.Web.Compilation;
using System.Web.Hosting;

[assembly: PreApplicationStartMethod(typeof(Core.Modules.ModuleManager), "Initialize")]
namespace Core.Modules
{
    public class ModuleManager
    {
        static ModuleManager()
        {
            string moduleStartPath = HostingEnvironment.MapPath("~/Modules");
            if (moduleStartPath == null)
                throw new DirectoryNotFoundException("Modules");
            ModuleStartFolder = new DirectoryInfo(moduleStartPath);

            string webBinPath = HostingEnvironment.MapPath("~/bin");
            if (string.IsNullOrEmpty(webBinPath))
                throw new DirectoryNotFoundException("bin");
            WebBinPath = webBinPath;
        }

        /// <summary>
        /// The Module Definition Start folder
        /// </summary>
        private static readonly DirectoryInfo ModuleStartFolder;
        private static readonly string WebBinPath;

        public static readonly Dictionary<string, IModuleDefinition> ModuleDefinitions = new Dictionary<string,IModuleDefinition>();


        /// <summary>
        /// Initialize method that registers all plugins
        /// </summary>
        public static void Initialize()
        {
            Array.ForEach(ModuleStartFolder.GetDirectories(), n => 
            {
                CopyAssembly(n);
            });
            InitializeModule(new DirectoryInfo(WebBinPath)); 
        }

        private static void CopyAssembly(DirectoryInfo directory)
        {
            var dirs = directory.GetDirectories("bin", SearchOption.TopDirectoryOnly);
            if (dirs == null || dirs.Length == 0)
                return;
            var binFolder = dirs.FirstOrDefault();

            try
            {
                var assemblies = binFolder.GetFiles("*.dll", SearchOption.AllDirectories);
                Array.ForEach(assemblies, n => {
                        n.CopyTo(WebBinPath + "\\" + n.Name, true);
                });
            }
            catch (Exception ex)
            {
                var logger = new Logger();
                logger.LogError(ex.Message, ex);
            }
        }

        private static void InitializeModule(DirectoryInfo directory)
        {

            try
            {
                //AppDomain.CurrentDomain.AppendPrivatePath(directory.FullName);
                var assemblies = directory.GetFiles("*.dll", SearchOption.AllDirectories)
                        .Select(x => AssemblyName.GetAssemblyName(x.FullName))
                        .Select(x => Assembly.Load(x.FullName));
                //var assemblies = binFolder.GetFiles(string.Format("{0}.dll", directory.Name), SearchOption.TopDirectoryOnly)
                //        .Select(x => AssemblyName.GetAssemblyName(x.FullName))
                //        .Select(x => Assembly.Load(x.FullName));
                foreach (var assembly in assemblies)
                {
                    //Add the plugin as a reference to the application
                    BuildManager.AddReferencedAssembly(assembly);

                    Type type = assembly.GetTypes().Where(t => t.GetInterface(typeof(IModuleDefinition).Name) != null).FirstOrDefault();
                    if (type != null && !type.IsAbstract && !type.IsInterface)
                    {
                        var module = (IModuleDefinition)Activator.CreateInstance(type);
                        if (!ModuleDefinitions.ContainsKey(module.ModuleFolder))
                        {
                            ModuleDefinitions.Add(module.ModuleFolder, module);
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                var logger = new Logger();
                logger.LogError(ex.Message,ex);
            }
        }

    }
}

关注点：

1. 以下特性标识 在APP的开始执行任何方法之前执行ModuleManager中的方法Initialize.

[assembly: PreApplicationStartMethod(typeof(Core.Modules.ModuleManager), "Initialize")]

2. 找到web站点目录。关键是类HostingEnvironment里有关于运行环境的一些处理方法。详细参见：http://msdn.microsoft.com/zh-cn/library/1677yx1a%28VS.80%29.aspx

string moduleStartPath = HostingEnvironment.MapPath("~/Modules");

3. AppDomain类的应用，参见：http://www.cnblogs.com/foman/archive/2009/10/18/1585655.html

AppDomain.CurrentDomain.AppendPrivatePath(directory.FullName);

4. DirectoryInfo, FileInfo, File类的应用，主要用于查找文件，Copy文件。

5. AssemblyName,Assembly加载DLL.

6. BuildManager类的应用，主要用于管理Asp.net的编译

7. Activator类用于创建对象。