Demonstrates how to upload a file using a controller action in ASP.NET MVC.

UploadImage

/// <summary>
/// POST: /UploadImage
/// Saves an image to the server, resizing it appropriately.
/// </summary>
/// <returns>A JSON response.</returns>
[HttpPost]
public ActionResult UploadImage(int id)
{
    // Validate we have a file being posted
    if (Request.Files.Count == 0)
    {
        return Json(new { statusCode = 500, status = "No image provided." }, "text/html");
    }

    // File we want to resize and save.
    var file = Request.Files[0];

    try
    {
        var filename = UploadFile(file);

        // Return JSON
        return Json(new
        {
            statusCode = 200,
            status = "Image uploaded.",
            file = filename,
        }, "text/html");
    }
    catch (Exception ex)
    {
        // Log using "NLog" NuGet package
        Logger.ErrorException(ex.ToString(), ex);
        return Json(new
        {
            statusCode = 500,
            status = "Error uploading image.",
            file = string.Empty
        }, "text/html");
    }
}

/// <summary>
/// Persist the file to disk.
/// </summary>
private string UploadFile(HttpPostedFileBase file)
{
    // Initialize variables we'll need for resizing and saving
    var width = int.Parse(ConfigurationManager.AppSettings["AuthorThumbnailResizeWidth"]);
    var height = int.Parse(ConfigurationManager.AppSettings["AuthorThumbnailResizeHeight"]);
    
    // Build absolute path
    var absPath = @"C:\path\to\file\";
    var absFileAndPath = absPath + file.FileName;

    // Create directory as necessary and save image on server
    if (!Directory.Exists(absPath))
        Directory.CreateDirectory(absPath);
    file.SaveAs(absFileAndPath);

    // Resize image using "ImageResizer" NuGet package.
    var resizeSettings = new ImageResizer.ResizeSettings
    {
        Scale = ImageResizer.ScaleMode.DownscaleOnly,
        Width = width,
        Height = height,
        Mode = ImageResizer.FitMode.Crop
    };
    var b = ImageResizer.ImageBuilder.Current.Build(absFileAndPath, resizeSettings);

    // Save resized image
    b.Save(absFileAndPath);

    // Return relative file path
    return relativeFileAndPath;
}