Question

我的MVC 4应用程序内置了一个文件上传模块。目前，如果用户选择文件并上传，系统工作正常，但如果用户尝试单击“提交”按钮而未选择任何文件，则我的应用程序将抛出异常。我查看了我的代码，但我无法弄清楚导致异常的原因。

以下是我正在使用的代码。

FileUploadController动作：FileUpload：

 // Get the posted file and upload it
    [Authorize]
    [HttpPost]
    public ActionResult FileUpload(HttpPostedFileBase file)
    {
        //throw new Exception("Something went wrong");
        // Get the user ID
        int user_id;
        // Maximum file size 10MB
        //int maxSize = 10485760;
        // Get the maximum size allowed from web.config
        int maxSize = Int32.Parse(ConfigurationManager.AppSettings["MaxFileSize"]);

        user_id = WebSecurity.CurrentUserId;
        if (file.ContentLength > 0 && file.ContentLength < maxSize)
        {
            try
            {
                if (file.ContentLength > 0)
                {

                    var fileName = Path.GetFileName(file.FileName);
                    var fileType = Path.GetExtension(file.FileName);
                    var fileLength = file.ContentLength;

                    var uploadLocation = ConfigurationManager.AppSettings["UploadLocation"];

                    //Response.Write("Length: " + fileLength);
                    //Response.End();

                    switch (fileType.ToString())
                    {
                        // Potential bad extensions
                        // bat exe cmd sh php pl cgi 386 dll com torrent js app jar pif vb vbscript wsf asp cer csr jsp drv sys ade adp bas chm cpl crt csh fxp hlp hta inf ins isp jse htaccess htpasswd ksh lnk mdb mde mdt mdw msc msi msp mst ops pcd prg reg scr sct shb shs url vbe vbs wsc wsf wsh
                        // Block .exe etc  
                        case ".exe":
                        case ".cmd":
                        case ".msi":
                        case ".dll":
                        case ".com":
                        case ".torrent":
                        case ".js":
                        case ".wsh":
                        case ".vbs":
                        case ".asp":
                        case ".cs":
                        case ".vb":
                            ViewBag.Message = "ECTU Secure File Upload - File type not supported: '" + fileType.ToString() + "'";
                            return View();
                        default:
                            // Create a GUID for our stored filename
                            Guid fileGUID = Guid.NewGuid();
                            // Create the file path
                            //var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileGUID.ToString());
                            var path = Path.Combine(uploadLocation, fileGUID.ToString());
                            // Upload the file
                            file.SaveAs(path);
                            // Log in DB the file information that has been uploaded
                            int varLogFile = logFileInfo(user_id, fileName, path, fileType, fileGUID.ToString());
                            break;
                    }

                }
                else
                {
                    ViewBag.Message = "ECTU Secure File Upload - No file selected.";
                    return View();
                }
            }
            catch (Exception ex)
            {
                // No file selected
                // Return to view with error message
                ViewBag.Message = ex.ToString(); // "ECTU Secure File Upload - Please select a file to upload.";
                return View();
            }
        }
        else
        {
              ViewBag.Message = "ECTU Secure File Upload - File is too big: " + (file.ContentLength / 1024) + "kb";
              return View();
        }
        //returnto the view with a success message
        ViewBag.Message = "ECTU Secure File Upload - Upload Successful: " + file.FileName;
        return View();
    }

Razor html视图：FileUpload.cshtml

@{
ViewBag.Title = "FileUpload";
}

<hgroup class="title">
    <h1>@ViewBag.Message</h1>
</hgroup>

<article>
<br />
<form action="" method="post" enctype="multipart/form-data">
  <input type="file" name="file" id="file" />
  <input type="submit" formaction="FileUpload" value="Submit">
</form>


<p><span class="instructions">Instructions: </span> Select a file to upload. Please note that executable (.exe) files are not supported. All files must be less than 1.9 Gb. Please refer to the user guide for more information.</p>

<p>@Html.ActionLink("Back to List", "Uploader", "Upload")</p>
</article>

这是完整的错误代码和堆栈跟踪：

Object reference not set to an instance of an object.
System.Web.HttpException (0x80004005): A public action method 'Uploadermvc error Object reference not set to an instance of an object' was not found on controller 'SecureFileUploadTraining.Controllers.UploadController'.

   at System.Web.Mvc.Controller.HandleUnknownAction(String actionName)

   at System.Web.Mvc.Controller.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult)

   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)

   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()

   at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult)

   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)

   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()

   at System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult)

   at System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult)

   at System.Web.Mvc.MvcHandler.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult)

   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)

   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()

   at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)

   at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)

   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()

   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

感谢您提供有关此问题的任何帮助。

Answer 1

尽管这些人已经回答过，但你应该在你的方法中实现if-then-now catch。

public ActionResult FileUpload(HttpPostedFileBase file)
{
   if(file == null)
   throw new ArgumentException("file")


   // Now perform the rest of the method.

}

在此控制器方法被命中之前，您应确保文件已在客户端上传。

对象引用未设置为文件上载系统的对象实例

1 个答案: