File input empty but an empty "file" shows up in Request.Files

Question

I have a view that has the following file input:

<input type="file" name="SchemaFiles" id="SchemaFiles" class="form-control" multiple/>

My model has this attribute:

  public List<HttpPostedFileBase> SchemaFiles { get; set; }

When I select one or two files for this input, everything works fine. However, if I don't select any files and submit the form, then SchemaFiles.Count is 1, and SchemaFiles[0] is null (but does exist). ModelState.IsValid is true.

Is there a way to avoid this?

That code in the model is c#. I guess it's more of an asp.net-mvc question (tagged) though. Does that really warrant a downvote? — Dave, Dec 29 '15 at 22:50

score 2 · Accepted Answer · edited May 23 '17 at 10:32

2

This is by-design and looks like the root cause is the browser. See these links for reference:

ASP.NET work item: http://aspnetwebstack.codeplex.com/workitem/188
Stackoverflow article: Why IEnumerable<HttpPostedFileBase> count is 1 when I upload 0 files? and
Blog article: http://michaelsync.net/2014/04/29/asp-net-mvc-multiple-files-upload-bug-or-by-design-issue

edited May 23 '17 at 10:32

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answered Dec 29 '15 at 23:03

Haukman

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I'll see if the browsers have a bug report or explanation. – Dave Dec 29 '15 at 23:06
I think most browsers will do it this way, probably legacy reasons that will just stick. My point is that the data coming in over HTTP has an empty filename when no files are selected (at least according to these posts) and the correct way to solve this is to filter it out in your server code. In general you should always distrust data coming from the browser, always check and filter out invalid data. – Haukman Dec 29 '15 at 23:24

File input empty but an empty "file" shows up in Request.Files

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