ASP.NET VirtualPathProvider (下)

上一篇介绍了VirtualPathProvider中虚拟文件的实现，参考：ASP.NET VirtualPathProvider (上)。
文件系统中，只有文件是不完整的，还要有目录。本篇介绍VirtualPathProvider中的虚拟目录实现。

实现代码：

using System.Collections;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Web;
using System.Web.Caching;
using System.Web.Hosting;

namespace Xianfen.Net.MyVirtualPathProvider_Directory
{
    public class MyVirtualPathProvider : VirtualPathProvider
    {
        public static void AppInitialize()
        {
            HostingEnvironment.RegisterVirtualPathProvider(new MyVirtualPathProvider());
        }

        bool IsVirtualFile(string vPath)
        {
            return Regex.IsMatch(vPath, @".*vfile\d{1}\.aspx", RegexOptions.IgnoreCase);
        }

        bool IsVirtualDirectory(string vPath)
        {
            string relativePath = VirtualPathUtility.ToAppRelative(vPath);

            return Regex.IsMatch(relativePath, @"~/vdir\d{1}/.*", RegexOptions.IgnoreCase);
        }

        public override bool FileExists(string virtualPath)
        {
            if (IsVirtualFile(virtualPath))
            {
                return true;
            }
            else
            {
                return Previous.FileExists(virtualPath);
            }
        }

        public override CacheDependency GetCacheDependency(string virtualPath, IEnumerable virtualPathDependencies, System.DateTime utcStart)
        {
            if (IsVirtualFile(virtualPath))
            {
                return null;
            }
            else
            {
                return base.GetCacheDependency(virtualPath, virtualPathDependencies, utcStart);
            }
        }

        public override bool DirectoryExists(string virtualDir)
        {
            if (IsVirtualDirectory(virtualDir))
            {
                return true;
            }
            else
            {
                return base.DirectoryExists(virtualDir);
            }
        }

        public override VirtualDirectory GetDirectory(string virtualDir)
        {
            if (IsVirtualDirectory(virtualDir))
            {
                return new MyVirtualDirectory(virtualDir);
            }
            else
            {
                return Previous.GetDirectory(virtualDir);
            }
        }

        public override VirtualFile GetFile(string virtualPath)
        {
            virtualPath = virtualPath.ToLower();

            if (IsVirtualFile(virtualPath))
            {
                return new MyVirtualFile(virtualPath);
            }
            else
            {
                return Previous.GetFile(virtualPath);
            }
        }
    }
}

namespace Xianfen.Net.MyVirtualPathProvider_Directory
{
    public class MyVirtualFile : VirtualFile
    {
        private string myPath;

        public MyVirtualFile(string virtualPath)
            : base(virtualPath)
        {
            myPath = virtualPath;
        }

        public override Stream Open()
        {
            Stream stream = new MemoryStream();
            StreamWriter sw = new StreamWriter(stream);
            StreamReader sr = null;

            try
            {
                string content = File.ReadAllText(HttpContext.Current.Server.MapPath("~/App_Data/htm.txt"), Encoding.UTF8);
                content = content.Replace("$currentfile$", myPath);

                sw.Write(content);
                sw.Flush();
                stream.Seek(0, SeekOrigin.Begin);

                return stream;
            }
            finally
            {
                if (sr != null)
                {
                    sr.Close();
                    sr.Dispose();
                }
            }
        }
    }

    public class MyVirtualDirectory : VirtualDirectory
    {
        string vDir = null;
        ArrayList children = new ArrayList();
        ArrayList dirs = new ArrayList();
        ArrayList files = new ArrayList();

        public MyVirtualDirectory(string virtualDirectory)
            : base(virtualDirectory)
        {
            vDir = virtualDirectory;
            InitData();
        }

        private void InitData()
        {
            if (string.IsNullOrEmpty(vDir))
            {
                children.Add("vdir1");
                children.Add("vdir2");
                children.Add("vdir3");
                children.Add("vdir4");

                dirs.Add("vdir1");
                dirs.Add("vdir2");
                dirs.Add("vdir3");
                dirs.Add("vdir4");

                children.Add("vfile1.aspx");
                children.Add("vfile2.aspx");
                children.Add("vfile3.aspx");
                children.Add("vfile4.aspx");

                files.Add("vfile1.aspx");
                files.Add("vfile2.aspx");
                files.Add("vfile3.aspx");
                files.Add("vfile4.aspx");
            }
            else
            {
                children.Add("vfile1.aspx");
                children.Add("vfile2.aspx");
                children.Add("vfile3.aspx");
                children.Add("vfile4.aspx");

                files.Add("vfile1.aspx");
                files.Add("vfile2.aspx");
                files.Add("vfile3.aspx");
                files.Add("vfile4.aspx");
            }
        }

        public override System.Collections.IEnumerable Children
        {
            get { return children; }
        }

        public override System.Collections.IEnumerable Directories
        {
            get { return dirs; }
        }

        public override System.Collections.IEnumerable Files
        {
            get { return files; }
        }
    }
}

首先定义了虚拟路径提供者，然后实现了虚拟文件和虚拟目录。值得一提的是，实现虚拟路径时，必须重载VirtualPathProvider的GetCacheDependency方法，可以实现自己的CacheDependency或直接返回null，否则会抛出找不到目录的异常。

运行截图：