.NET Web MVC

File Upload

The following code example illustrates how to handle file upload on your server using .Net Web MVC as a server-side language. For step by step explanation of the upload flow see file upload concept.

Frontend

The main index page.

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <!-- Include Editor style. -->
  <link href="https://cdn.jsdelivr.net/npm/froala-editor@3.0.0-beta.1/css/froala_editor.pkgd.min.css" rel="stylesheet" type="text/css" />
</head>

<body>
  <!-- Include Editor JS files. -->
  <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/froala-editor@3.0.0-beta.1//js/froala_editor.pkgd.min.js"></script>

  <div class="sample">
    <h2>File upload example.</h2>
    <form>
      <textarea id="edit" name="content"></textarea>
    </form>
  </div>

  <!-- Initialize the editor. -->
  <script>
    new FroalaEditor('#edit', {
      // Set the file upload URL.
      fileUploadURL: '/UploadFiles',

      fileUploadParams: {
        id: 'my_editor'
      }
    })
  </script>
</body>
</html>

Backend

HomeController.cs file is the default controller that will be used in this example to define the upload part. The uploads directory will be automatically created if it dose not exist under wwwroot/upload/. The root directory must be write available otherwise the upload directory will not be created.

The HomeController will manage the request and the upload part, so you should define the following functions in this file. After processing the uploaded file, if it passes the validation, the server will respond with a JSON object containing a link to the uploaded file.

E.g.: {"link":"http://server_address/upload/name_of_file"}.

public class HomeController : Controller
{
  public ActionResult UploadFiles()
  {
    if (Request.Files["file"] != null)
    {
      HttpPostedFileBase MyFile = Request.Files["file"];

      // Setting location to upload files
      string TargetLocation = Server.MapPath("~/Files/");

      try
      {
        if (MyFile.ContentLength > 0)
        {
          // Get File Extension
          string Extension = Path.GetExtension(MyFile.FileName);

          // Determining file name. You can format it as you wish.
          string FileName = Path.GetFileName(MyFile.FileName);
          FileName = Guid.NewGuid().ToString().Substring(0, 8);

          // Determining file size.
          int FileSize = MyFile.ContentLength;

          // Creating a byte array corresponding to file size.
          byte[] FileByteArray = new byte[FileSize];

          // Basic validation for file extension
          string[] AllowedExtension = { ".txt", ".pdf", ".doc", ".json", ".html"};
          string[] AllowedMimeType = { "text/plain", "application/msword", "application/x-pdf", "application/pdf", "application/json","text/html" };

          if (AllowedExtension.Contains(Extension) && AllowedMimeType.Contains(MimeMapping.GetMimeMapping(MyFile.FileName)))
          {
            // Posted file is being pushed into byte array.
            MyFile.InputStream.Read(FileByteArray, 0, FileSize);

            // Uploading properly formatted file to server.
            MyFile.SaveAs(TargetLocation + FileName + Extension);
            string json = "";
            Hashtable resp = new Hashtable();
            string urlPath = MapURL(TargetLocation) + FileName + Extension;

            // Make the response an json object
            resp.Add("link", urlPath);
            json = JsonConvert.SerializeObject(resp);

            // Clear and send the response back to the browser.
            Response.Clear();
            Response.ContentType = "application/json; charset=utf-8";
            Response.Write(json);
            Response.End();
          }
          else
          {
            // Handle validation errors
          }
        }
      }

      catch (Exception ex)
      {
        // Handle errors
      }
    }
    return View();
  }

  // Convert file path to url
  // http://stackoverflow.com/questions/16007/how-do-i-convert-a-file-path-to-a-url-in-asp-net
  private string MapURL(string path)
  {
    string appPath = Server.MapPath("/").ToLower();
    return string.Format("/{0}", path.ToLower().Replace(appPath, "").Replace(@"\", "/"));
  }
}