c# - 如何使用Entity Framework从另一个类返回ID或全部？

我正在学习Entity Framework，所以如果这对您来说容易就不要怪我

我有班级HomeNumber.cs

    [ScaffoldColumn(false)]
    [Key]
    public int HomeNumberId { get; set; }
    //[ForeignKey("HomeNumberId")]
    //public virtual HomeNumber HomeNumbers { get; set; }

    [Required(ErrorMessage = "Polje kućni broj je obavezno!")]
    public string HomeNumberName { get; set; }

    [Required(ErrorMessage = "Polje pod broj/slovo je obavezno!")]
    public string HomeSubNumber { get; set; }

    public int StreetId { get; set; }
    [ForeignKey("StreetId")]
    public virtual Street Street { get; set; }

    ....

    public bool AddHomeNumber(string homeNumberName, string homeSubNumber, Street street)
    {
        HomeNumber number = new HomeNumber();
        number.HomeNumberName = homeNumberName;
        number.HomeSubNumber = homeSubNumber;
        number.StreetId = street.StreetId;

        using (var _db = new DataContext())
        {
            // Dodaj HomeNumber u bazu [AD_HOMENUMBER]
            _db.DB_HomeNumber.Add(number);
            _db.SaveChanges();
        }
        // Success.
        return true;
    }

和Street.cs类

    [ScaffoldColumn(false)]
    [Key]
    public int StreetId { get; set; }

    [Required(ErrorMessage = "Polje naziv ulice je obavezno!")]
    public string StreetName { get; set; }

    .....

    public bool AddStreet(string streetName)
    {
        Street street = new Street();
        street.StreetName = streetName;

        using (var _db = new DataContext())
        {
            // Dodaj Street u bazu [AD_STREET]
            _db.DB_Street.Add(street);
            _db.SaveChanges();
        }
        // Success.
        return true;
    }

我的背后代码是：

    Street st = new Street();
    st.AddStreet(ucAddress.Street.Text);

    HomeNumber hou = new HomeNumber();
    hou.AddHomeNumber(ucAddress.HouseNumber.Text, ucAddress.HouseSubNumber.Text, st.StreetId);

我需要在我的背后代码st.streetId中添加值，...我不知道我缺少什么，...因为在AddHomeNumber中，我调用street.StreetId，其中st.streetId为返回值

最佳答案

我认为您要在AddStreet上执行的操作如下所示。您保存Street并返回结果。

public Street AddStreet(string streetName)
{
    Street street = new Street();
    street.StreetName = streetName;

    using (var _db = new DataContext())
    {
        // Dodaj Street u bazu [AD_STREET]
        _db.DB_Street.Add(street);
        _db.SaveChanges();
    }
    // Success.
    return street;
}

在后面的代码中，您在st中传递了st.StreetId而不是AddHomeNumber。

Street st = new Street();
st = st.AddStreet(ucAddress.Street.Text); // get the street that has been saved with generated id.

HomeNumber hou = new HomeNumber();
hou.AddHomeNumber(ucAddress.HouseNumber.Text, ucAddress.HouseSubNumber.Text, st);

注意：我建议您看一下Repository模式，这将使您的生活更轻松，并且将编写更具可读性和更出色的代码。



Street的基本存储库对于HomeNumber或以相同方式创建存储库的其他实体也将类似。

public class StreetRepository
{
    private DataContext _db;
    public StreetRepository(DataContext dataContext)
    {
        _db = dataContext;
    }

    public Street Add(string streetName)
    {
        Street street = new Street();
        street.StreetName = streetName;

        using (var _db = new DataContext())
        {
            // Dodaj Street u bazu [AD_STREET]
            _db.DB_Street.Add(street);
            _db.SaveChanges();
        }
        // Success.
        return street;
    }

    public Street Get(int id)
    {
        return _db.DB_Street.Find(id);
    }

    // other CRUD methods
}

用法：

StreetRepository streetRepository = new StreetRepository();
HomeNumberRepository homeNumberRepository = new HomeNumberRepository(); // you have to create it yourself

Street st = streetRepository.Add(ucAddress.Street.Text); // get the street that has been saved with generated id.

HomeNumber homeNumber = homeNumberRepository.Add(ucAddress.HouseNumber.Text, ucAddress.HouseSubNumber.Text, st);

注意：您可能会发现为每个实体编写一个存储库都很痛苦，这里有帮助通用存储库。

掌握了Repository模式之后，您可以转到工作单元并发现EntityFramework已经有了它。