ImageUploaderController gives error during image uploading to editor

i have copy this controller from dancing goat sample project, it gives error when i create object of "HttpPostedFileWrapper file" in if condition, any help will be highly appreciated

if (!(Request.Files[requestFileName] is HttpPostedFileWrapper file))

{

return Guid.Empty;

}

var directoryPath = EnsureUploadDirectory();

var imagePath = GetTempFilePath(directoryPath, file);

byte[] data = new byte[file.ContentLength];

file.InputStream.Seek(0, System.IO.SeekOrigin.Begin);

file.InputStream.Read(data, 0, file.ContentLength);