.NET Image Validation

How it works

  1. The image gets uploaded to your server.
  2. Before storing the image on disk, it is being validated on server side.

Jump to Complete Example

Image Upload

In the Server Upload article we explain the steps to upload an image on your server. When you insert an image in the rich text editor, you can validate its format. However that check is done only on the filename and not on the mime type. We recommend to make additional checks on server side just to make sure that users don't upload images in bad formats.

Validate Extension

The WYSIWYG editor's .NET SDK comes with the possibility to check the image extension when it is being stored on the disk. Additional to the file name extension, it is using the mime type of the file for better accuracy.

FroalaEditor.ImageOptions options = new FroalaEditor.ImageOptions
{
    Fieldname = "file",
    Validation = new FroalaEditor.ImageValidation(new string[] { "gif", "jpeg", "jpg", "png", "svg", "blob" }, new string[] { "image/gif", "image/jpeg", "image/pjpeg", "image/x-png", "image/png", "image/svg+xml" })
};

object response = FroalaEditor.Image.Upload(System.Web.HttpContext.Current, fileRoute, options);

Custom Validation

You can also pass a custom method instead of validating the extension and mime type. This gives you full control on what types of images you want to store on disk. Below is an example of how to validate if an image is square.

Func validationFunction = (filePath, mimeType) => {

    MagickImageInfo info = new MagickImageInfo(filePath);

    if (info.Width != info.Height)
    {
        return false;
    }

    return true;
};

FroalaEditor.ImageOptions options = new FroalaEditor.ImageOptions
{
    Fieldname = "file",
    Validation = new FroalaEditor.ImageValidation(validationFunction)
};


var image = new FroalaEditor.Image(System.Web.HttpContext.Current);
object response = image.Upload(fileRoute, options);

Complete Example

<script>
  $(function() {
    $('.selector').froalaEditor({
      // Set the image upload URL.
      imageUploadURL: '/FroalaApi/UploadImageValidation'
    })
  });
</script>
using System;
using System.Web.Mvc;

namespace demo.Controllers
{
    public class FroalaApiController : Controller
    {
        public ActionResult UploadImageValidation()
        {
            string fileRoute = "/Public/";

            FroalaEditor.ImageOptions options = new FroalaEditor.ImageOptions
            {
                Fieldname = "file",
                Validation = new FroalaEditor.ImageValidation(new string[] { "gif", "jpeg", "jpg", "png", "svg", "blob" }, new string[] { "image/gif", "image/jpeg", "image/pjpeg", "image/x-png", "image/png", "image/svg+xml" })
            };

            try
            {
                return Json(FroalaEditor.Image.Upload(System.Web.HttpContext.Current, fileRoute, options));
            }
            catch (Exception e)
            {
                return Json(e);
            }
        }
    }
}