Question

经过一番努力才能做到正确，我设法通过Neo4jClient将属性关系保存到Neo4j数据库。当我想要阅读这些关系时，问题就出现了。突然间，之前像魅力一样工作的查询不再返回我的用户了吗？没有异常被抛出，调用只是默默地返回空:(我读到了可能的反序列化问题，并将无参数构造函数添加到关系类但没有运气。

public class UserHasHomeCity : Relationship<HasHomeCity>, IRelationshipAllowingSourceNode<UserEntity>, IRelationshipAllowingTargetNode<CityEntity>
{
    public UserHasHomeCity()
        : base(-1, null)
    {
    }

    public UserHasHomeCity(NodeReference targetNode, HasHomeCity data)
        : base(targetNode, data)
    {
    }

    public const string TypeKey = "USER_HAS_HOME_CITY";
    public override string RelationshipTypeKey
    {
        get { return TypeKey; }
    }
}

public class HasHomeCity
{
    public string Date { get; set; }

    public HasHomeCity()
    { }

    public HasHomeCity(string date)
    {
        this.Date = date;
    }
}

这是我的疑问：

     var graphResults = graphClient.Cypher
            .Match("(user:User)-[:USER_IS_IN_ROLE]-(role:Role)",
            "(user:User)-[:USER_HAS_HOME_CITY]-(homeCity:City)-[:CITY_IS_IN_COUNTRY]-(homeCountry:Country)",
            "(user:User)-[:USER_HAS_LIVING_CITY]-(livingCity:City)-[:CITY_IS_IN_COUNTRY]-(livingCountry:Country)")
            .Where((UserEntity user) => user.Id == id)
            .Return((user, role, homeCity, livingCity, homeCountry, livingCountry) => new
            {
                User = user.As<UserEntity>(),
                Roles = role.CollectAs<RoleEntity>(),
                HomeCity = homeCity.As<CityEntity>(),
                LivingCity = livingCity.As<CityEntity>(),
                HomeCountry = homeCountry.As<CountryEntity>(),
                LivingCountry = livingCountry.As<CountryEntity>()
            }).Results;

Answer 1

Neo4jClient正在逐渐停止使用Relationship和Node类，所以，好消息是 - 您不再需要将关系定义为: Relationship了！事实上，根据您想要的程度，您甚至根本不需要UserHasHomeCity课程。

关系属性被视为与节点相同，因为它们只是POCO对象。

所以，为了创造（我相信你知道）我们做了类似的事情：

var userData = new User {Id = "Id-1"};
var cityData = new City {Name = "Brighton"};
var countryData = new Country {Name = "UK"};
var userHasHomeData = new HasHomeCity {Date = "April 1980"};
var generalData = new CountryRelationshipData { Area = "South Coast" };

gc.Cypher
    .Create("(country:Country {countryParams})")
    .WithParam("countryParams", countryData)
    .ExecuteWithoutResults();

gc.Cypher
    .Match("(country:Country)")
    .Where((Country country) => country.Name == "UK")
    .CreateUnique("(city:City {cityParams})-[:CITY_IS_IN_COUNTRY {relParams}]->(country)")
    .WithParam("cityParams", cityData)
    .WithParam("relParams", generalData)
    .ExecuteWithoutResults();

gc.Cypher
    .Match("(city:City)")
    .Where((City city) => city.Name == "Brighton")
    .Create("(user:User {userParams})-[:USER_HAS_HOME_CITY {relParams}]->(city)")
    .WithParam("userParams", userData)
    .WithParam("relParams", userHasHomeData )
    .ExecuteWithoutResults();

将为我们提供(User)-[:USER_HAS_HOME_CITY]-(City)结构。

要检索关系属性，我们可以使用此查询：

var query = gc.Cypher
    .Match("(user:User)-[r:USER_HAS_HOME_CITY]-(city:City)-[r1:CITY_IS_IN_COUNTRY]-(country:Country)")
    .Where((User user) => user.Id == "Id-1")
    .Return((user, city, r, country, r1) =>
        new
        {
            User = user.As<User>(),
            City = city.As<City>(),
            HasHome = r.As<HasHomeCity>(),
            Country = country.As<Country>(),
            CountryRel = r1.As<CountryRelationshipData>()
        });

并循环结果（在这种情况下所有1个）：

var res = query.Results.ToList();
foreach (var result in res)
    Console.WriteLine("User ({0}) home city: {1} (which is in {2}, {3}) since {4}", result.User.Id, result.City.Name,result.CountryRel.Area,  result.Country.Name, result.HasHome.Date );

会给我们：

User (Id-1) home city: Brighton (which is in South Coast, UK) since April 1980

作为输出。

如何从Neo4jClient获取与属性的关系

1 个答案: