缺少程序集引用和方法必须具有返回类型?！MVC 4

im在mvc 4中工作，并尝试实现jquery文件上传器。

但是在我的FileStatus类和UploadHandler中给了我几个错误。

-找不到命名空间FileStatus，

-方法FileStatus需要一个返回类型。

我有一个例子，已经看到方法FileStatus不返回任何东西，

我不知道发生了什么事。

有人能帮忙吗？

FIleStatusCLASS

public class FileStatus
    {
        public const string HandlerPath = "/Upload/";
        public string group { get; set; }
        public string name { get; set; }
        public string type { get; set; }
        public int size { get; set; }
        public string progress { get; set; }
        public string url { get; set; }
        public string thumbnail_url { get; set; }
        public string delete_url { get; set; }
        public string delete_type { get; set; }
        public string error { get; set; }
        public FilesStatus() { }
        public FilesStatus(FileInfo fileInfo) { SetValues(fileInfo.Name, (int)fileInfo.Length, fileInfo.FullName); }
        public FilesStatus(string fileName, int fileLength, string fullPath) { SetValues(fileName, fileLength, fullPath); }
        private void SetValues(string fileName, int fileLength, string fullPath)
        {
            name = fileName;
            type = "image/png";
            size = fileLength;
            progress = "1.0";
            url = HandlerPath + "UploadHandler.ashx?f=" + fileName;
            delete_url = HandlerPath + "UploadHandler.ashx?f=" + fileName;
            delete_type = "DELETE";
            var ext = Path.GetExtension(fullPath);
            var fileSize = ConvertBytesToMegabytes(new FileInfo(fullPath).Length);
            if (fileSize > 3 || !IsImage(ext)) thumbnail_url = "/Content/img/generalFile.png";
            else thumbnail_url = @"data:image/png;base64," + EncodeFile(fullPath);
        }
        private bool IsImage(string ext)
        {
            return ext == ".gif" || ext == ".jpg" || ext == ".png";
        }
        private string EncodeFile(string fileName)
        {
            return Convert.ToBase64String(System.IO.File.ReadAllBytes(fileName));
        }
        static double ConvertBytesToMegabytes(long bytes)
        {
            return (bytes / 1024f) / 1024f;
        }
    }

上传处理器

public class UploadHandler : IHttpHandler
    {
        private readonly JavaScriptSerializer js;
        private string StorageRoot
        {
            get { return Path.Combine(System.Web.HttpContext.Current.Server.MapPath("~/Files/")); } //Path should! always end with '/'
        }
        public UploadHandler()
        {
            js = new JavaScriptSerializer();
            js.MaxJsonLength = 41943040;
        }
        public bool IsReusable { get { return false; } }
        public void ProcessRequest(HttpContext context)
        {
            context.Response.AddHeader("Pragma", "no-cache");
            context.Response.AddHeader("Cache-Control", "private, no-cache");
            HandleMethod(context);
        }
        // Handle request based on method
        private void HandleMethod(HttpContext context)
        {
            switch (context.Request.HttpMethod)
            {
                case "HEAD":
                case "GET":
                    if (GivenFilename(context)) DeliverFile(context);
                    else ListCurrentFiles(context);
                    break;
                case "POST":
                case "PUT":
                    UploadFile(context);
                    break;
                case "DELETE":
                    DeleteFile(context);
                    break;
                case "OPTIONS":
                    ReturnOptions(context);
                    break;
                default:
                    context.Response.ClearHeaders();
                    context.Response.StatusCode = 405;
                    break;
            }
        }
        private static void ReturnOptions(HttpContext context)
        {
            context.Response.AddHeader("Allow", "DELETE,GET,HEAD,POST,PUT,OPTIONS");
            context.Response.StatusCode = 200;
        }
        // Delete file from the server
        private void DeleteFile(HttpContext context)
        {
            var filePath = StorageRoot + context.Request["f"];
            if (File.Exists(filePath))
            {
                File.Delete(filePath);
            }
        }
        // Upload file to the server
        private void UploadFile(HttpContext context)
        {
            var statuses = new List<FilesStatus>();
            var headers = context.Request.Headers;
            if (string.IsNullOrEmpty(headers["X-File-Name"]))
            {
                UploadWholeFile(context, statuses);
            }
            else
            {
                UploadPartialFile(headers["X-File-Name"], context, statuses);
            }
            WriteJsonIframeSafe(context, statuses);
        }
        // Upload partial file
        private void UploadPartialFile(string fileName, HttpContext context, List<FilesStatus> statuses)
        {
            if (context.Request.Files.Count != 1) throw new HttpRequestValidationException("Attempt to upload chunked file containing more than one fragment per request");
            var inputStream = context.Request.Files[0].InputStream;
            var fullName = StorageRoot + Path.GetFileName(fileName);
            using (var fs = new FileStream(fullName, FileMode.Append, FileAccess.Write))
            {
                var buffer = new byte[1024];
                var l = inputStream.Read(buffer, 0, 1024);
                while (l > 0)
                {
                    fs.Write(buffer, 0, l);
                    l = inputStream.Read(buffer, 0, 1024);
                }
                fs.Flush();
                fs.Close();
            }
            statuses.Add(new FilesStatus(new FileInfo(fullName)));
        }
        // Upload entire file
        private void UploadWholeFile(HttpContext context, List<FilesStatus> statuses)
        {
            for (int i = 0; i < context.Request.Files.Count; i++)
            {
                var file = context.Request.Files[i];
                var fullPath = StorageRoot + Path.GetFileName(file.FileName);
                file.SaveAs(fullPath);
                string fullName = Path.GetFileName(file.FileName);
                statuses.Add(new FilesStatus(fullName, file.ContentLength, fullPath));
            }
        }
        private void WriteJsonIframeSafe(HttpContext context, List<FilesStatus> statuses)
        {
            context.Response.AddHeader("Vary", "Accept");
            try
            {
                if (context.Request["HTTP_ACCEPT"].Contains("application/json"))
                    context.Response.ContentType = "application/json";
                else
                    context.Response.ContentType = "text/plain";
            }
            catch
            {
                context.Response.ContentType = "text/plain";
            }
            var jsonObj = js.Serialize(statuses.ToArray());
            context.Response.Write(jsonObj);
        }
        private static bool GivenFilename(HttpContext context)
        {
            return !string.IsNullOrEmpty(context.Request["f"]);
        }
        private void DeliverFile(HttpContext context)
        {
            var filename = context.Request["f"];
            var filePath = StorageRoot + filename;
            if (File.Exists(filePath))
            {
                context.Response.AddHeader("Content-Disposition", "attachment; filename='"" + filename + "'"");
                context.Response.ContentType = "application/octet-stream";
                context.Response.ClearContent();
                context.Response.WriteFile(filePath);
            }
            else
                context.Response.StatusCode = 404;
        }
        private void ListCurrentFiles(HttpContext context)
        {
            var files =
                new DirectoryInfo(StorageRoot)
                    .GetFiles("*", SearchOption.TopDirectoryOnly)
                    .Where(f => !f.Attributes.HasFlag(FileAttributes.Hidden))
                    .Select(f => new FilesStatus(f))
                    .ToArray();
            string jsonObj = js.Serialize(files);
            context.Response.AddHeader("Content-Disposition", "inline; filename='"files.json'"");
            context.Response.Write(jsonObj);
            context.Response.ContentType = "application/json";
        }
    }

对于UploadHandler，我使用这个：
使用系统
使用System.Collections.Generic
使用System.Linq
使用System.Web
使用System.IO
使用System.Web.Script.Serialization

对于fileclass，这是：
使用系统
使用System.Collections.Generic
使用System.Linq
使用System.Web
使用System.IO

我知道它有很多代码，对此我很抱歉，但我认为最好向您展示所有的代码。

提前感谢您的帮助。

public class FileStatus

public FilesStatus(FileInfo fileInfo)