Prevent Double Submit / Post on ASP.NET MVC page

Question

I am hoping for some feedback about the method I intend to use for preventing duplicate records in an ASP.NET MVC 4 application, and the knock on effects I have not though o

Answer 1

Sometimes, deal with it only on client side isn't enought. Try to gen a hash code of the form and save in cache (set an expiration date or something like that).

the algorithm is something like:

1- User made post

2- Generate hash of the post

3- Check the hash in cache

4- Post already on cache? Throw exception

5- Post isn't on cache? Save the new hash on cache and save post on database

A sample:

            //verify duplicate post
            var hash = Util.Security.GetMD5Hash(String.Format("{0}{1}", topicID, text));
            if (CachedData.VerifyDoublePost(hash, Context.Cache))
                throw new Util.Exceptions.ValidadeException("Alert! Double post detected.");

The cache function could be something like that:

    public static bool VerifyDoublePost(string Hash, System.Web.Caching.Cache cache)
    {
        string key = "Post_" + Hash;

        if (cache[key] == null)
        {
            cache.Insert(key, true, null, DateTime.Now.AddDays(1), TimeSpan.Zero);
            return false;
        }
        else
        {
            return true;
        }
    }