In this article I will explain with an example, how to solve the problem i.e. IFormFile always returns NULL when used in Controller while uploading files in ASP.Net Core (.Net Core 8) MVC.
There are two reasons. First the name of the IFormFile parameter and the name of HTML FileUpload element must be exact same and second that the Form element must be specified with the enctype attribute.
Note: For beginners in ASP.Net Core (.Net Core 8) MVC, please refer my article ASP.Net Core 8: Hello World Tutorial with Sample Program example.
 
 

Controller

The Controller consists of following Action methods.

Action method for handling GET operation

Inside this Action method, simply the View is returned.
 

Action method for handling Post operation

This Action method accepts the parameter which is collection of type IFormFile.
Note: The name of the IFormFile parameter and the name of HTML FileUpload element must be exact same, otherwise the IFormFile parameter will be NULL.
 
Inside this Action method, first a check is performed whether Directory (Folder) exists if not then the Directory (Folder) is created inside the www Folder using IWebHostingEnvironment interface and then a loop is executed and one by one each file is saved to the Directory (Folder).
Note: For more details on how to use IWebHostEnvironment in ASP.Net Core, please refer my article Using IWebHostEnvironment in ASP.Net Core.
 
Finally, a message is displayed to the user using ViewBag.
Note: 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
{
    private IWebHostEnvironment Environment;
 
    public HomeController(IWebHostEnvironment _environment)
    {
        this.Environment = _environment;
    }
 
    public IActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public IActionResult Index(List<IFormFile> postedFiles)
    {
        string wwwPath = this.Environment.WebRootPath;
        string contentPath = this.Environment.ContentRootPath;
 
        string path = Path.Combine(this.Environment.WebRootPath, "Uploads");
        if (!Directory.Exists(path))
        {
            Directory.CreateDirectory(path);
        }
 
        List<string> uploadedFiles = new List<string>();
        foreach (IFormFile postedFile in postedFiles)
        {
            string fileName = Path.GetFileName(postedFile.FileName);
            using (FileStream stream = new FileStream(Path.Combine(path, fileName), FileMode.Create))
            {
                postedFile.CopyTo(stream);
                uploadedFiles.Add(fileName);
                ViewBag.Message += string.Format("<b>{0}</b> uploaded.<br />", fileName);
            }
        }
 
        return View();
    }
}
 
 

View

HTML Markup

The View consists of an HTML Form created with following Razor Tag Helpers attributes.
asp-action – Name of the Action. In this case the name is Index.
asp-controller – Name of the Controller. In this case the name is Home.
method – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
Note: The Form element must be specified with enctype attribute and its value must be multipart/form-data, otherwise the IFormFile parameter will be NULL.
 
There is an HTML FileUpload element, a Submit Button and a SPAN element for displaying Message enclosed in a Form element.
The HTML FileUpload element has been specified with an additional HTML5 attribute multiple = “multiple” in order to allow user to select multiple files.
@{
     Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <form method="post" enctype="multipart/form-data" asp-controller="Home" asp-action="Index">
        <span>Select File:</span>
        <input type="file" name="postedFiles" multiple="multiple" />
        <input type="submit" value="Upload" />
        <br /><br />
        <span style="color:green">@Html.Raw(ViewBag.Message)</span>
    </form>
</body>
</html>
 
 

Screenshot

ASP.Net Core: IFormFile always returns NULL
 
 

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