我们做项目时有时候不想添加别的项目的引用，但是那个项目又必须在 Global 中进行注册

最常见的就是插件机制,参考： 

我们知道如果不添加引用在主程序中是无法使用其程序集的

我们可以自己加载其程序集

推荐做法是将dll文件先copy到 AppDomain.CurrentDomain.DynamicDirectory 中

然后在 AppDomain.CurrentDomain.DynamicDirectory 中进行 Assembly.Load

下面的代码没有进行copy了

1、命名空间顶部的程序开始时加载程序集必须添加，其中的2个参数分别时当前类及要执行的方法

2、使用Assembly.Load对程序集进行加载

[assembly: PreApplicationStartMethod(typeof(PatulouManager), "Initialize")]namespace IdeaSite.Web.Framework{    public class PatulouManager    {        private const string PatulousPath = "~/Patulous";        public static void Initialize()        {            var patulouFolder = new DirectoryInfo(MapPath(PatulousPath));            var patulouFiles = patulouFolder.GetFiles("*.dll", SearchOption.AllDirectories);            foreach (var patulouFile in patulouFiles.Where(x => !IsAlreadyLoaded(x)))            {                var shadowCopiedAssembly = Assembly.Load(AssemblyName.GetAssemblyName(patulouFile.FullName));                BuildManager.AddReferencedAssembly(shadowCopiedAssembly);            }        }        /// 
        /// 获取物理路径        /// 
        ///         /// 
             public static string MapPath(string path)        {            if (HostingEnvironment.IsHosted)            {                //hosted                return HostingEnvironment.MapPath(path);            }            //not hosted. For example, run in unit tests            string baseDirectory = AppDomain.CurrentDomain.BaseDirectory;            path = path.Replace("~/", "").TrimStart('/').Replace('/', '\\');            return Path.Combine(baseDirectory, path);        }        /// 
        /// 是否已加入程序集        /// 
        ///         /// 
             private static bool IsAlreadyLoaded(FileInfo fileInfo)        {            try            {                string fileNameWithoutExt = Path.GetFileNameWithoutExtension(fileInfo.FullName);                if (fileNameWithoutExt == null)                    throw new Exception(string.Format("Cannot get file extension for {0}", fileInfo.Name));                foreach (var a in AppDomain.CurrentDomain.GetAssemblies())                {                    string assemblyName = a.FullName.Split(new[] { ',' }).FirstOrDefault();                    if (fileNameWithoutExt.Equals(assemblyName, StringComparison.InvariantCultureIgnoreCase))                        return true;                }            }            catch (Exception exc)            {                Debug.WriteLine("Cannot validate whether an assembly is already loaded. " + exc);            }            return false;        }    }}