如何正确扩展 IdentityUser 以保存每个用户的集合

Question

我希望用户能够从 MultiSelectList 下拉列表中选择多个技能。我能够将每个用户的多个技能选择保存到数据库中，但我发现如果我删除一个用户的技能选项，并且我使用之前在他的选择中保存了相同技能的不同用户登录，它会已为此用户和所有其他保存了类似技能选项的用户删除。

所以我很清楚。假设用户 A 保存了这些技能 [“C#”、“Python”、“Java”]。用户 B 当前保存的技能是 ["C++","Scala"]。用户 B 然后登录并决定添加他刚刚学习的 C#。一旦他更新了他的个人资料并且他的选择变成了这个[“C++”，“Scala”，“C#”]。 C# 会从用户 A 的选择中删除，因此它变为 ["Python", "Java"]。

这是我自定义的IdentityUser 类。

public class ApplicationUser : IdentityUser
{
    public ApplicationUser()
    {
        Skills = new List<Skill>();
    }
    public string Location { get; set; }
    public virtual ICollection<Skill> Skills { get; set; }
}

这是技能模型。

public class Skill
{
    public int SkillId { get; set; }
    public string SkillType { get; set; }
}

这就是我在控制器中保存技能选择的方式。

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Profile(ProfileViewModel profileModel)
{
    var user = await _userManager.GetUserAsync(User);

    if (user == null)
    {
        return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
    }
    if (ModelState.IsValid)
    {
        if (user.Location != profileModel.Location) user.Location = profileModel.Location;

        if (profileModel.SelectedSkillIds != null)
        {
            List<Skill> tempSkills = new List<Skill> { };
            foreach (var skillID in profileModel.SelectedSkillIds)
            {
                user.Skills.Add(_context.Skills.FirstOrDefault(x => x.SkillId == skillID));
                var skill = _context.Skills.Find(skillID);
                if (skill != null)
                {
                    user.Skills.Add(skill);
                    tempSkills.Add(skill);
                }
                var allSkills = _context.Skills.ToList();
                var skillsToRemove = allSkills.Except(tempSkills);
                foreach (var sk in skillsToRemove)
                {
                    user.Skills.Remove(sk);
                }
            }
            await _userManager.UpdateAsync(user);
            await _signInManager.RefreshSignInAsync(user);
            return RedirectToAction("Profile", "Account");
        }
        return View(profileModel);
    }
}

更新 - 我如何删除选择

if (profileModel.SelectedSkillIds != null)
{
    List<UserSkill> tempSkills = new List<UserSkill> { };
    foreach (var skillID in profileModel.SelectedSkillIds)
    {
        var skill = _context.Skills.Find(skillID);
        if (skill != null)
        {
            var userskill = new UserSkill { AppUserId = user.Id, SkillId = skill.SkillId };
            user.UserSkills.Add(userskill);
            tempSkills.Add(userskill);
        }
    var allSkills = _context.UserSkills.ToList();
    var skillsToRemove = allSkills.Except(tempSkills);
    foreach (var sk in skillsToRemove)
    {
        user.UserSkills.Remove(sk); 
    }
}

Answer 1

您应该创建一个像UserSkills 这样的类，它具有UserId 和SkillId，在这种情况下，任何用户都可以拥有多种技能，并且任何技能都可以用于许多用户。见many-to-many,1,2

你应该把你的模型改成这个

public class ApplicationUser : IdentityUser
{
    public ApplicationUser()
    {
        Skills = new List<Skill>();
    }
    public string Location { get; set; }
    public virtual ICollection<UserSkills> Skills { get; set; }
}
public class Skill
{
    public int SkillId { get; set; }
    public string SkillType { get; set; }
    public virtual ICollection<UserSkills> Skills { get; set; }
}
public class UserSkills
{
    public int Id { get; set }
    public int UserId { get; set }
    public int SkillId { get; set }
    public Skill Skill { get; set; }
    public ApplicationUser User { get; set; }
}

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Profile(ProfileViewModel profileModel)
{
    var user = await _userManager.GetUserAsync(User);

    if (user == null)
    {
        return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
    }
    if (ModelState.IsValid)
    {
        if (user.Location != profileModel.Location) user.Location = profileModel.Location;

        if (profileModel.SelectedSkillIds != null)
        {
            List<Skill> tempSkills = new List<Skill> { };
            foreach (var sk in user.UserSkills)
            {
               user.UserSkills.Remove(sk);
            }
            foreach (var skillID in profileModel.SelectedSkillIds)
            {
                var userSkills = new UserSkill { UserId = user.Id, SkillId = skillID };
                user.UserSkills.Add(userSkills);
            }
            await _userManager.UpdateAsync(user);
            await _signInManager.RefreshSignInAsync(user);
            return RedirectToAction("Profile", "Account");
        }
        return View(profileModel);
    }
}

然后将UserSkills 添加到您的DbContext

public DbSet<Skill> Skills { get; set; }
public DbSet<UserSkill> UserSkills { get; set; }

最后在package manager console中使用Add-Migration和Update-DataBase

其他选项

您可以在控制器中注入DbContext 并在UserSkill 表中添加UserSkills 数据

private readonly YourDbContext _dbContext;
public UserController(YourDbContext dbContext)
{
    _dbContext = dbContext;
}
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Profile(ProfileViewModel profileModel)
{
    var user = await _userManager.GetUserAsync(User);

    if (user == null)
    {
        return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
    }
    if (ModelState.IsValid)
    {
        if (user.Location != profileModel.Location) user.Location = profileModel.Location;

        if (profileModel.SelectedSkillIds != null)
        {
            var userSkillsForDelete = _dbContext.UserSkills.Where(a => a.UserId == user.Id).ToList();//<-- NOTE THIS
            foreach (var sk in userSkillsForDelete)
            {
               //user.UserSkills.Remove(sk);
               _dbContext.UserSkills.Remove(sk);<--NOTE THIS
            }
            foreach (var skillID in profileModel.SelectedSkillIds)
            {
                var userSkills = new UserSkill { UserId = user.Id, SkillId = skillID };
               _dbContext.UserSkills.Add(userSkills);<--NOTE THIS
            }
            await _userManager.UpdateAsync(user);
            await _signInManager.RefreshSignInAsync(user);
            return RedirectToAction("Profile", "Account");
        }
        return View(profileModel);
    }
}