//Dictionary which will hold result parameters
            Dictionary qryParams = new Dictionary();

            //Sample URL for testing
            String urlToconvert = "http://www.mysite.com?ArtId=valu1&CatId=value2&SubCatId=value3";


            //Actual LINQ query 
            var query = from item in urlToconvert.Split('?').Where(m => m.Contains('='))
                            .SelectMany(pr => pr.Split('&'))
                        where item.Contains('=')
                        select new KeyValuePair(
                            item.Split('=')[0],
                            item.Split('=')[1]);
            query.ToList().ForEach(kvp => qryParams.Add(kvp.Key, kvp.Value));