MVC2 - File upload with HttpPostedFileBase

ASP.NET MVC2 makes it extremely easy to upload a file to your controller.

Scott Hanselman blogged about this in detail

http://www.hanselman.com/blog/ABackToBasicsCaseStudyImplementingHTTPFileUploadWithASPNETMVCIncludingTestsAndMocks.aspx

The article is a bit dated, so there are a few small tweaks for MVC 2.

View

<% using(Html.BeginForm("Upload CSV", "Customer", FormMethod.Post, new { enctype = "multipart/form-data" })){ %>
<%: Html.ValidationSummary() %>

    <input type\="file" id\="fileUpload" name\="fileUpload"/>

    <input type\="submit" value\="Upload file" />

<% } %>

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You need to use FormMethod.Post
You need to make sure encoding type is multipart/form-data - otherwise the server will not receive anything!
ValidationSummary isn’t really needed, but you might want some place to throw up some errors.
The name of the input type=“file” needs to match the argument in the controller, in my case “fileUpload”

Controller

    \[HttpPost\]
    public virtual ActionResult UploadCustomer(HttpPostedFileBase fileUpload)
    {
        if (fileUpload == null)
        {
            // problem
            return;
        }
        if (fileUpload.ContentLength == 0)
       {
            // problem
            return;
       }

       var reader = new StreamReader(fileUpload.InputStream);

The binder will automatically take the uploaded file and stick it in the HttpPostedFileBase class.
You can check it’s status, and then grab the InputStream and read (and write out) the stream if you need to.

Gotchas

Some AJAX libraries sometimes like to hijack a Form submit. In our case, it was turning the multipart/form-data back to application/x-www-form-urlencoded - which will not work.

If fileUpload remains null in the controller, check your Request object on the controller and see what’s the encoding used on the post back.

View

Controller

Gotchas

Discussions