实体框架 - 具有多对多表的用户和组

Question

I have run into an issue that has me going around in circles. What I need to implement is users and groups in our website. We are using Entity Framework (database first) with ASP.NET in C#.

Here are the requirements:

1. There are users
2. There are groups (which are created by the administrator and will exist in the DB)
3. Each users can be in one or more groups
4. Each group can have 0 or more users.

The current Groups are: Administrator Board of Directors Editors

So in short, "User1" can be in both the Editor & Board of Directors groups but not a member of the Administrator group.

First I constructed my database with a Users, a Groups and a UserGroups table. The userGroups table has the following fields:

 User Group ----------- ------------ UserId (PK) GroupId (PK) Name Name ... ... \\ / UserGroup ------------- UserGroupTestID (PK) UserId (FK) GroupId (FK)

The problem with this approach is that EF will not let me add more than 1 user to this table throwing a "Multiplicity constraint violated" error since it was a 1 User to Many relationship.

So I changed it to be a many-to-many table by dropping the PK as follows:

User              Group
-----------       ------------
UserId (PK)       GroupId (PK)
Name              Name
...               ...

       \           /
          UserGroup
         -------------
          UserId (FK)
          GroupId (FK)

I was now able to access user.Group and was able to add a group to this user. When I was adding a user to a group, I was querying the existing groups and adding it like this:

user.Groups.Add( ctx.Groups.Where( g => g.GroupID == 12 ).First( );

The problem is that this created a new group for this user in the Groups table - even though the ID of the Group was correct (12) when it was saved to the database.

I need to do the following things:

1. Create a user and put the new user in 1 or more groups.
2. Edit an existing user to add or remove them from groups.

I am sure that I am doing something wrong (and probably bone-headed), but if anyone can help me to achieve this, I would really appreciate it.

Thanks in advance!

Code in Admin_AddUser.aspx.cs:

User user = new User( );
user.CustomerID = CustomerID;
user.IsClub = false;
user.IsDistrict = true;
user.FirstName = txtFirstName.Text;
user.LastName = txtLastName.Text;
user.Email = txtEmail.Text;
user.Password = txtPassword.Text;
user.AccountActive = true;

foreach( RadListBoxItem item in lbSelectedRoles.Items )
{
  user.Roles.Add( UserData.GetRole( DCManager.Instance.SiteSettings.Customer.CustomerID, int.Parse( item.Value ) ) );
}

bool rtn = UserData.CreateUser( user );
...

Code in CreateUser method:

public static bool CreateUser( User user )
{
  using ( var ctx = new DCEntities( ) )
  {
    //Check if the login credentials already exist
    if ( ctx.Users.Where( u => u.Email == user.Email
                           && u.Password == user.Password ).Count( ) > 0 )
      return false;
    else
    {
      ctx.Users.Add( user );
      ctx.SaveChanges( );

      return true;
    }
  }
}

=========================

In my project, the Groups and actually called "Roles"

Since the UserGroups table in the DB is a many-to-many, it is not show in the EDMX file, but the Users & Groups (Roles in my db) are linked as many-to-many.

Mapping Details:

Answer 1

If I understood your question correctly. I would recommend you do the following:

1. Create a table UsersAndGroups (int: PK, UserId: FK, GroupId: FK).
2. Establish relationships between Users and UsersAndGroups as one-to-many.
3. Establish relationships between Groups and UsersAndGroups as one-to-many.
4. Remove relationship between Users and Groups.

This will allow you the following:

1. Add User to one or more groups by adding rows to UsersAndGroups table.
2. Get User groups by selecting all records with certain UserId from UsersAndGroups table.
3. Get Group users by selecting all records with certain GroupId from UsersAndGroups table.

Hope I understood you right.

Answer 2

Using code first:

To Roles add

public virtual List<User> Users { get; set; }

To Users add

public virtual List<Role> Roles { get; set; }

Your classes might look like this

using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;


namespace MyProject.EFTest
{
    public class Role
    {
        [Key]
        public int RoleID { get; set; }

        [Required]
        [StringLength(100)]
        public string Name { get; set; }

        public virtual List<User> Users { get; set; }

    }

    public class User
    {
        [Key]
        public int UserID { get; set; }

        public string Name { get; set; }

        public virtual List<Role> Roles { get; set; }

    }

}

When the migration is generated EF will create table UserRole in addition to Users and Roles

    CreateTable(
        "dbo.UserRole",
        c => new
            {
                User_UserID = c.Int(nullable: false),
                Role_RoleID = c.Int(nullable: false),
            })
        .PrimaryKey(t => new { t.User_UserID, t.Role_RoleID })
        .ForeignKey("dbo.User", t => t.User_UserID)
        .ForeignKey("dbo.Role", t => t.Role_RoleID)
        .Index(t => t.User_UserID)
        .Index(t => t.Role_RoleID);