Transforming http request into linq query

I wrote something that has probably done thousands of times: a function that takes a parsed http query as input and return a linq query.

Any input is appreciated.

public IList<Lead> GetLeads(NameValueCollection nvc)
{
    IQueryable<MyContext> queryBase = QueryBase();

    foreach (string key in nvc)
    {
        const string format = "dd-MM-yyyy";

        if (nvc[key] == "all")
            continue;


        //case where an array of possible values is sent
        const string regex = "\\[.*\\]";


        Expression<Func<MyContext, bool>> predicate = c => false;

        string[] values = nvc[key].Split(',');
        foreach (string value in values)
        {
            Expression<Func<MyContext, bool>> predicateTemp;
            DateTime date;
            switch (Regex.Replace(key, regex, ""))
            {
                case "nature":
                    string value1 = value;
                    predicateTemp =
                        c => c.Typologies.NatureDemande == value1;
                    break;
                case "departementCode":
                    string value2 = value;
                    predicateTemp = c => c.Geographies.DepartementCode == value2;
                    break;
                case "start":
                    String start = value;
                    date = DateTime.ParseExact(start, format, null);

                    DateTime date1 = date;
                    predicateTemp = c => c.Temps.Date >= date1;
                    break;
                case "end":
                    String end = value;
                    date = DateTime.ParseExact(end, format, null);

                    DateTime date2 = date;
                    predicateTemp = c => c.Temps.Date <= date2;
                    break;
                default:
                    predicateTemp =
                        c => true;
                    break;
            }
            predicate = OrElse(predicate, predicateTemp);
        }


        queryBase = queryBase.Where(predicate);
    }

    //query all leads
    IQueryable<Lead> query = (from x in queryBase
                              select new Lead
                                  {
                                      id = Convert.ToInt32(x.Leads.DemandeWeb_FK),
                                      lng = Convert.ToDouble(x.Leads.longitudeClient.Replace(",", ".")),
                                      lat = Convert.ToDouble(x.Leads.latitudeClient.Replace(",", ".")),
                                      temps = Convert.ToInt32(x.Leads.GeolocDureeTrajetDistrib),
                                      distance = Convert.ToInt32(x.Leads.GeolocDistanceRouteDistrib),
                                      nature = x.Typologies.NatureDemande,
                                      type = x.Distributeurs.DistribType,
                                      reseau = x.Distributeurs.ReseauDistributeur,
                                      instance = x.Demands.IdInstance,
                                      distribution = Convert.ToInt32(x.Distributeurs.DistribIdPointDeVente),
                                  });


    return query.ToList();
}