實體框架EF6將數據添加到多對多關系表

Question

我有很多對很多的關系，這使我可以向表中添加多個投訴和員工。 我對EF相當陌生。

這將比我已經擁有的要簡單，但這將有助於解決我的問題：

雇員：

public class Employee
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

}

投訴：

   public class Complaint
    {
        public int Id { get; set; }
        public string Description { get; set; } 
    }

ComplaintXEmployee：

public class ComplaintXEmployee
{
    public ComplaintXEmployee()
    {
        Employees = new HashSet<Employee>();
        Complaints = new HashSet<Complaint>();
    }

    public int ComplaintXEmployeeId { get; set; }
    public int EmployeeId { get; set; }
    public int ComplaintId { get; set; }

    public virtual ICollection<Employee> Employees { get; set; }
    public virtual ICollection<Complaint> Complaints { get; set; } 
}

主要

    static void Main(string[] args)
    {
        var complaintList = new List<Complaint>()
        {
            new Complaint() {Description = "This is a Test"}
        };

        var employeeList = new List<Employee>()
        {
            new Employee() {FirstName = "John", Id = 1, LastName = "Doe"},
            new Employee() {FirstName = "Jane", Id = 2, LastName = "Doe"},
            new Employee() {FirstName = "Kid", Id = 3, LastName = "Smith"}
        };

        var c = new ComplaintXEmployee();

        //from here I dont know

        using (var context = new FakeEntities())
        {
            context.ComplaintXEmployees.Add(c);
            context.SaveChanges();
        }
    }

如何將兩個列表都添加到ComplaintXEmployees？

Answer 1

您需要做的第一件事是將導航屬性添加到您的實體。 （我添加了一些額外的屬性只是為了好玩）

[Table("Employee")] //can be Employees
public class Employee
{
    [Key]
    public int Id { get; set; }

    [StringLenth(64)]
    public string FirstName { get; set; }

    [StringLenth(64)]
    public string LastName { get; set; }

    public virtual ICollection<Complaint> Complaints { get; set; } 
}    

[Table("Complaint")] //can be Complaints
public class Complaint
{
    [Key]
    public int Id { get; set; }

    [StringLenth(128)]
    public string Description { get; set; } 

    public virtual ICollection<Employee> Employees { get; set; }
}

要手動定義中間表-在DbContext中，您可以像下面這樣使用FluentApi：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder
            .Entity<Employee>()
            .HasMany(fa => fa.Complaints)
            .WithMany(u => u.Employees)
            .Map(m => m.MapLeftKey("EmployeeId")
                 .MapRightKey("ComplaintId")
                 .ToTable("ComplaintXEmployee"));
}

屬性

[Key]告訴實體框架，它必須使用此“列”作為表的主鍵。

[StringLenth（128）]告訴實體框架列的長度為128。指定長度總是更好的，否則實體框架將假定其為NVARCHAR（MAX）。

[Table（“ Employee”）]告訴實體框架您要使用的表名。 如果不考慮這一點，它將使用類名的復數形式。

Answer 2

您不需要手動添加多對多表，因為EF會為您完成：

public class Employee
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public virtual ICollection<Complaint> Complaints { get; set; } 
}    

public class Complaint
{
    public int Id { get; set; }
    public string Description { get; set; } 

    public virtual ICollection<Employee> Employees { get; set; }
}

此類聲明將自動生成表。 在實體之間添加關系很簡單：

static void Main(string[] args)
{
    using (var context = new FakeEntities())
    {
        var complaintList = new List<Complaint>()
        {
            new Complaint() {Description = "This is a Test"}
        };
        Context.Complaint.AddRange(complaintList);

        var employeeList = new List<Employee>()
        {
            new Employee() {FirstName = "John", Id = 1, LastName = "Doe"},
            new Employee() {FirstName = "Jane", Id = 2, LastName = "Doe"},
            new Employee() {FirstName = "Kid", Id = 3, LastName = "Smith"}
        };
        Context.Employee.AddRange(employeeList);

        //Just add entities to corresponding collections.
        employeeList[0].Complaints.Add(complaintList[0]);

        context.SaveChanges();
    }
}

Answer 3

奇怪的是，那里的行事率高達99％。

是因為您沒有聲明任何鍵和關系...如果是這樣，那么肖恩·索爾本的另一個答案更好！

static void Main(string[] args)
{
    var complaintList = new List<Complaint>()
    {
        new Complaint() {Description = "This is a Test"}
    };

    var employeeList = new List<Employee>()
    {
        new Employee() {FirstName = "John", Id = 1, LastName = "Doe"},
        new Employee() {FirstName = "Jane", Id = 2, LastName = "Doe"},
        new Employee() {FirstName = "Kid", Id = 3, LastName = "Smith"}
    };

    var c = new ComplaintXEmployee();
    c.Employees = employeeList;
    c.Complaints = complaintList;

    using (var context = new FakeEntities())
    {
        context.ComplaintXEmployees.Add(c);
        context.SaveChanges();
    }
}