.NET WebForms

Image Upload

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

Frontend

This can be pasted in your Default.aspx

<!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>Image upload example.</h2>
    <form>
      <textarea id="edit" name="content"></textarea>
    </form>
  </div>

  <!-- Initialize the editor. -->
  <script>
    new FroalaEditor('#edit', {
      // Set the image upload URL.
      imageUploadURL: '/Upload',

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

Backend

Upload.aspx file handles the request and the upload part. The uploads directory will be automatically created if it dose not exist under "project_root"/Files/. The project root directory must be write available otherwise the Files folder will not be created.

Inside the Upload file the following functions need to be defined. After processing the uploaded image, if it passes the validation, the server will respond with a JSON object containing a link to the uploaded image.

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

public partial class Upload : Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
    if (Request.Files["file"] != null)
    {
      HttpPostedFile 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);

          // Generate random name.
          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 = { ".gif", ".jpeg", ".jpg", ".png", ".svg", ".blob" };

          // Basic validation for mime type
          string[] AllowedMimeType = { "image/gif", "image/jpeg", "image/pjpeg", "image/x-png", "image/png", "image/svg+xml" };

          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 upload errors.
          }
        }
      }

      catch (Exception ex)
      {
        // Handle errors
      }
    }
  }

  // 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(@"\", "/"));
  }
}