HttpPostedFileBase always return null in ASP.NET M

问题:

I have a problem when I upload a file in ASP.NET MVC. My code is below:

View:

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Index2</h2>
@using (Html.BeginForm("FileUpload", "Board", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
  <input type="file" />
  <input type="submit" />
}

Controller:

[HttpPost]
public ActionResult FileUpload(HttpPostedFileBase uploadFile)
{
    if (uploadFile != null && uploadFile.ContentLength > 0)
    {
        string filePath = Path.Combine(Server.MapPath("/Temp"), Path.GetFileName(uploadFile.FileName));
        uploadFile.SaveAs(filePath);
    }
    return View();
}

But uploadFile always returns null. Can anyone figure out why??

回答1:

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Index2</h2>
@using (Html.BeginForm("FileUpload", "Board", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
  <input type="file" name="uploadFile"/>
  <input type="submit" />
}

you have to provide name to input type file to uploadFile in order to model binding work in ASP.net mvc and
also make sure that name of your input type file and argument name of HttpPostedFileBase is identical.

回答2:

I had tried most of the solutions posted online for this topic, but found it better to use a workaround instead..

It really didn't matter what I did the HttpPostedFileBase and/or HttpPostedFile were always null. Using the HttpContext.Request.Files collection seemed to work with no hassles at all.

e.g.

 if (HttpContext.Request.Files.AllKeys.Any())
        {
            // Get the uploaded image from the Files collection
            var httpPostedFile = HttpContext.Request.Files[0];

            if (httpPostedFile != null)
            {
                // Validate the uploaded image(optional)

                // Get the complete file path
                var fileSavePath =(HttpContext.Server.MapPath("~/UploadedFiles") + httpPostedFile.FileName.Substring(httpPostedFile.FileName.LastIndexOf(@"\")));

                // Save the uploaded file to "UploadedFiles" folder
                httpPostedFile.SaveAs(fileSavePath);
            }
        }

In the above example I only grab the first file, but it is just a matter of looping though the collection to save all files.

HTH

Rob

回答3:

In my scenario the problem was with id attribute, I had this:

<input type="file" name="file1" id="file1" />

The soultion was to remove id:

<input type="file" name="file1"  />

回答4:

While not the answer to this specific user, I would like to point out that HTML requires that the form tag has an enctype attribute with the value multipart/form-data. And of course both the attribute and it's value must be correct.

For mvc, this means that when using beginform, you should use the version with the htmlAttributes parameter

回答5:

There can be another scenario also. In my case, I was getting this issue because I was directly rendering script tag in my MVC view and IE is giving issue there.

Correct code in view should be as below:

@section scripts
{
    <script>
        $(document).ready(function () {
            $('.fileinput').fileinput();
...
}