一段用于地址清洗的代码

            using (var context = new Entities())
            {
                // 使用前2个字符中匹配省级行政区划
                var provs = context.region.Where(r => r.Grade == 0);
                var prov = provs.SingleOrDefault(p => p.Alias.Contains(address.Substring(0, 2)));

                region city;
                if (prov == null)
                {
                    // 省级区划未知时，尝试使用前四个字符进行市级行政区划反向查询
                    city = (from c in context.region.Where(r => r.Grade == 1 && address.Substring(0, 4).Contains(r.Alias))
                            let index = address.IndexOf(c.Alias, StringComparison.OrdinalIgnoreCase)
                            where index >= 0
                            orderby index
                            select c).FirstOrDefault();
                    if (city == null) return result.BadRequest();

                    prov = context.region.Single(r => r.ID == city.ParentId);
                }
                else
                {
                    // 在已知的省级区划中匹配市级行政区划
                    city = (from c in context.region.Where(r => r.ParentId == prov.ID)
                            let index = address.IndexOf(c.Alias, StringComparison.OrdinalIgnoreCase)
                            where index >= 0
                            orderby index
                            select c).FirstOrDefault();
                }

                region county;
                if (city == null)
                {
                    // 市级区划未知时，在已知的省级区划中尝试使用县级行政区划反向查询
                    var citys = context.region.Where(r => r.ParentId == prov.ID);
                    county = (from c in context.region.Where(r => citys.Any(c => c.ID == r.ParentId))
                              let index = address.IndexOf(c.Alias, StringComparison.OrdinalIgnoreCase)
                              where index >= 0
                              orderby index
                              select c).FirstOrDefault();
                    if (county == null) return result.BadRequest();

                    city = context.region.Single(r => r.ID == county.ParentId);
                }
                else
                {
                    // 在已知的市级区划中匹配县级行政区划
                    county = (from c in context.region.Where(r => r.ParentId == city.ID)
                              let index = address.IndexOf(c.Alias, StringComparison.OrdinalIgnoreCase)
                              where index >= 0
                              orderby index
                              select c).FirstOrDefault();
                }

                // 移除省市县三级行政区划字符串
                var idx = address.IndexOf(county == null ? city.Alias : county.Alias, StringComparison.OrdinalIgnoreCase);
                var street = address.Substring(idx).Replace(county == null ? city.Name : county.Name, "");
                var region = new Address
                {
                    Prov = prov.Name,
                    City = city.Name,
                    County = county?.Name,
                    Street = street
                };
                return result.Success(region);
            }