Question

我正在尝试导航到与其他对象相关的对象。

在这种情况下，有2个班级; StockTakeSession 和位置。这两者具有一对一的关系。当每个类创建2个对象时，我按照下面的代码设置关系。我可以随心所欲地浏览它，没有任何问题。但是当我从数据库中获取StockTakeSession时，只有LocationId有一个值，而Location本身为null。为了解决这个问题，我为StockTakeSession.Location创建了扩展的get方法。

我对C＃/ SQLite / ORM很新，所以我想知道这是假设它是如何工作还是我需要使用不同的方法？

感谢您的任何建议。

罗伯特

这是2个类：

// These are the Stock Take Sessions
public class StockTakeSession : DomainModels
{
    [PrimaryKey, AutoIncrement]
    public int Id { get; set; }
    public DateTime DateTime { get; set; }

    // Navigation properties
    // One to many relationship with StockItems
    [OneToMany(CascadeOperations = CascadeOperation.All)]
    public List<StockItem> StockItems { get; set; }


    // Specify the foreign key to Location
    [ForeignKey(typeof(Location))]
    public int LocationId { get; set; }

    // One to one relationship with Location

    private Location location;

    [OneToOne]
    public Location Location
    {


        get
        {
            if (location == null)
            {
                DataBase db = new DataBase();

                Location locationTemp = db.SelectLocation(LocationId);

                return locationTemp;
            }
            else
                return location;

        }

        set
        {
            location = value;
        }
    }
}

// These are the Locations where the Stock Take Sessions are done
public class Location : DomainModels, IComparable<Location>
{
    [JsonProperty("id"), PrimaryKey]
    public int Id { get; set; }
    public string Name { get; set; }
    public string Street { get; set; }
    public int Number { get; set; }
    public string Postcode { get; set; }
    public string City { get; set; }
    public bool Completed { get; set; }

    [Ignore]
    public string Label
    {
        get
        {
            return Name + " - (" + Postcode + ")";
        }
    }

    public int CompareTo(Location other)
    {
        return Name.CompareTo(other.Name);
    }

    // Navigation property
    // One to many relationship with StockItems
    [OneToMany(CascadeOperations = CascadeOperation.All), Ignore]
    public List<StockItem> StockItems { get; set; }

    // Specify the foreign key to StockTakeSession
    [ForeignKey(typeof(StockTakeSession))]
    public int StockTakeSessionId { get; set; }

    // One to one relationship with StockTakeSession
    [OneToOne]
    public StockTakeSession StockTakeSession { get; set; }

}

我如何存储对象之间的关系：

StockTakeSession newSession = new StockTakeSession
{
    LocationId = selectedLocation.Id,
    Location = selectedLocation,
    DateTime = DateTime.Now

};

db.Insert(newSession, true);

Answer 1

在sqlite-net-extensions中，不按需加载关系。您需要在需要时从数据库中获取它们。

将Location的实施更改为简单的getter / setter。

[OneToOne]
public Location Location { get; set; }

然后，在需要时加载会话关系：

db.GetChildren(session);

例如：

db.GetWithChildren<StockTakeSession>(stockId);

将使用该Id获取StockTakeSession对象，并加载关系并设置反向关系。

导航到与从数据库中提取的其他对象相关的SQLite对象

1 个答案: