In this article I will explain with an example, how to solve the problem i.e. HttpPostedFileBase always returns NULL when used in Controller while uploading files in ASP.Net MVC.
The name of the HttpPostedFileBase parameter and the name of HTML FileUpload element must be exact same, otherwise the HttpPostedFileBase parameter will be NULL.
 
Note: For beginners in ASP.Net MVC, please refer my article ASP.Net MVC Hello World Tutorial with Sample Program example.
 
View
The following View consists of an HTML FileUpload element, a Submit Button and a SPAN element for displaying Message enclosed in a Form element.
The HTML Form has been created using the Html.BeginForm method which accepts the following parameters.
ActionName

Name of the Action. In this case the name is Index.
ControllerName – Name of the Controller. In this case the name is Home.
FormMethod – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
HtmlAttributes – This array allows to specify the additional Form Attributes. Here we need to specify enctype = “multipart/form-data” which is necessary for uploading Files.
<html>
<head>
    <meta name="viewport" content="width=device-width"/>
    <title>Index</title>
</head>
<body>
    <div>
        @using (Html.BeginForm("Index", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))
        {
            <span>Select File:</span>
            <input type="file" name="postedFile"/>
            <hr/>
            <input type="submit" value="Upload"/>
            <br/>
            <span style="color:green">@ViewBag.Message</span>
        }
    </div>
</body>
</html>
 
 
Namespaces
You will need to import the following namespace.
using System.IO;
 
 
Controller
The Action method Index by default supports the GET operation and hence another overridden method for POST operation is created which accepts the parameter of type HttpPostedFileBase.
Note: The name of the HttpPostedFileBase parameter and the name of HTML FileUpload element must be exact same, otherwise the HttpPostedFileBase parameter will be NULL.
 
First a check is performed whether Directory (Folder) exists if not then the Directory (Folder) is created and then the file is saved to the Directory (Folder).
Finally a message is displayed to the user using ViewBag. For more details on displaying message using ViewBag, please refer my article Display (Pass) String Message from Controller to View in ASP.Net MVC.
public class HomeController : Controller
{
    // GET: Home
    [HttpGet]
    public ActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public ActionResult Index(HttpPostedFileBase postedFile)
    {
        if (postedFile != null)
        {
            string path = Server.MapPath("~/Uploads/");
            if (!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);
            }
 
            postedFile.SaveAs(path + Path.GetFileName(postedFile.FileName));
            ViewBag.Message = "File uploaded successfully.";
        }
 
        return View();
    }
}
 
 
Screenshot
ASP.Net MVC: HttpPostedFileBase always returns NULL
 
 
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