FileUpload

public class Upload
{
    public string Name { get; set; }
    [FileSize(655360)]
    [FileTypes("jpg,jpeg,png")]
    public HttpPostedFileBase File { get; set; }
}

[HttpPost]
[Authorize]
public ActionResult Upload(Upload upload)
{
    string path = @"D:\Temp\";

    if (ModelState.IsValid)
    {
        if (upload != null && upload.File != null)
        upload.File.SaveAs(path + WebMatrix.WebData.WebSecurity.CurrentUserId+"_"+DateTime.Now.ToShortDateString());

        return RedirectToAction("Index");
    }

return View();
}

[Authorize]
[HttpGet]
public ActionResult Upload()
{
    ViewBag.Message = "Opa!";
    return View();
}


@using (Html.BeginForm("Upload", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    <label for="file">Photo:</label>
    <input type="file" name="File"/>
    <input type="submit" />
}

public class FileSizeAttribute : ValidationAttribute
{
    private readonly int _maxSize;

    public FileSizeAttribute(int maxSize)
    {
        _maxSize = maxSize;
    }

    public override bool IsValid(object value)
    {
        if (value == null) return true;

        HttpPostedFileWrapper httpPostedFileWrapper = value as HttpPostedFileWrapper;
        return httpPostedFileWrapper != null && _maxSize > httpPostedFileWrapper.ContentLength;
    }

    public override string FormatErrorMessage(string name)
    {
        return string.Format("The file size should not exceed {0}", _maxSize);
    }
}

public class FileTypesAttribute : ValidationAttribute
{
    private readonly List<string> _types;

    public FileTypesAttribute(string types)
    {
        _types = types.Split(',').ToList();
    }

    public override bool IsValid(object value)
    {
        if (value == null) return true;

        HttpPostedFileWrapper httpPostedFile = value as HttpPostedFileWrapper;
        if (httpPostedFile != null)
        {
            var extension = System.IO.Path.GetExtension(httpPostedFile.FileName);
            if (extension != null)
            {
                var fileExt = extension.Substring(1);
                return _types.Contains(fileExt, StringComparer.OrdinalIgnoreCase);
            }
        }
        return true;
    }

    public override string FormatErrorMessage(string name)
    {
        return string.Format("Invalid file type. Only the following types {0} are supported.", String.Join(", ", _types));
    }
}