Get keys and errors from ModelStateDictionary

How can i get the keys and errors from the ModelStateDictionary? I have this piece of code, but it's done too many times and it throws me a duplicate key error.

    if (!modelstate.IsValid)
    {
        var errMessages = new Dictionary<string, string>();
        foreach (var item in modelstate.Keys)
        {
            foreach (var item2 in modelstate.Values)
            {
                foreach (var item3 in item2.Errors)
                {
                    errMessages.Add(item.ToLower(), item3.ErrorMessage);
                }
            }
        }
        return new Error { StatusCode = 409, ErrorMessages = errMessages };
    }

Thanks for all answers, have a nice day :D.

I managed to solve this problem, but if someone has better suggestions, I would like to read it.

if (!modelstate.IsValid)
        {
            var errMessages = new Dictionary<string, string>();
            var i = 0;
            foreach (var item2 in modelstate.Values.SelectMany(p => p.Errors))
            {
                var key = modelstate.Keys.ToArray();
                errMessages.Add(key[i].ToLower(), item2.ErrorMessage);
                i++;
            }
            return new Error { StatusCode = 409, ErrorMessages = errMessages };
        }