How to add Image Upload with Froala in Razor Pages?

Question

I'm trying to add Image Upload with Froala Editor to my Blog app.

My onPost method in NewPost.cshtml.cs file looks like this:

    public async Task<IActionResult> OnPostUploadImageAsync(IFormFile file)
    {
        if (file == null || file.Length == 0)
        {
            return BadRequest("No file uploaded");
        }

        try
        {
            var uploadResult = await _imageRepository.UploadAsync(file);

            if (uploadResult == null || string.IsNullOrEmpty(uploadResult.SecureUrl.AbsoluteUri))
            {
                return BadRequest("Failed to upload image");
            }

            return new JsonResult(new { url = uploadResult.SecureUrl.AbsoluteUri });
        }
        catch (Exception ex)
        {
            // Log the exception here
            return BadRequest("An error occurred while uploading the image");
        }
    }

And in my NewPost.cshtml file js script looks like this:

    <script>
        var editor = new FroalaEditor('#content', {
            height: 300,
            imageUploadURL: '/Admin/NewPost?handler=OnPostUploadImageAsync',


        })


        document.getElementById('featuredImageUpload').addEventListener('change', function () {
            var input = this;
            var imgPreview = document.getElementById('featuredImagePreview');
            var imageURLInput = document.getElementById('featuredImageURL');

            if (input.files && input.files[0]) {
                var reader = new FileReader();

                reader.onload = function (e) {
                    imgPreview.src = e.target.result;
                };

                reader.readAsDataURL(input.files[0]);

                imageURLInput.value = '@ViewData["FeaturedImageURL"]';
            }
        });  
    </script>

Now when i try to upload an image by froala I get 'Error during file upload' and in Chrome Console POST https://localhost:7006/Admin/NewPost?handler=OnPostUploadImageAsync 400 (Bad Request)

When I tried debugging I saw that the code in NewPost.cshtml.cs is unreachable, but I still did not find a solution.