SaveChangesAsync 失败，分配用户到对象 AspNetUsers 重复键违规

Question

我正在尝试创建一个项目可以有多个用户的项目项。您可以通过输入用户的姓名并按下按钮来分配用户；控制器将找到用户并返回用户（如果存在）。然后将它们添加到列表中，然后在项目创建提交时将其分配给项目。当项目使用 POST 时，SaveChangesAsync() 会产生一个带有错误的 http 响应 500：

    Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.
 ---> Microsoft.Data.SqlClient.SqlException (0x80131904): Violation of PRIMARY KEY constraint 'PK_AspNetUsers'. Cannot insert duplicate key in object 'dbo.AspNetUsers'. The duplicate key value is (fa2f3cdf-6147-4973-9c1e-988a21408610).
The statement has been terminated.

我似乎无法弄清楚为什么会发生这种情况，我觉得表单被提交了两次，或者通过两个按钮错误地提交了 Editform。我对 Blazor 和 EF 非常陌生，因此我希望能深入了解可能导致此问题的原因以及如何解决此问题。提前致谢

创建剃须刀页面

<EditForm Model="@projectItem" OnValidSubmit="@CreateNewProject">

<DataAnnotationsValidator />

<div class="form-group">
    <label class="custom-control-label"> Name </label>
    <InputText id="title" @bind-Value="projectItem.ProjectName" class="form-control" />
    <InputText id="title" @bind-Value="projectItem.ProjectDescription" class="form-control" />
    <ValidationMessage For="@(() => projectItem.ProjectName)" />

    <button type="submit" class="btn btn-primary">Create Project</button>

</div>

<ValidationSummary />
</EditForm>

<EditForm Model="@AssignUser" OnValidSubmit="@AddUserToProject">

<DataAnnotationsValidator />
<div class="form-group">
    <label class="custom-control-label"> Assign users </label>
    <InputText id="title" type="email" @bind-Value="@AssignUser.UserName" class="form-control" />

    <button type="submit" class="btn btn-primary">Add User</button>
</div>
</EditForm>

<p> Currently assigned users </p>

@if (ListOfAllUsers.Count() == 0)
{
    <p> No users assigned yet</p>
}
else
{
    @for(int i = 0; i < ListOfAllUsers.Count(); i++)
    {
        <li> @ListOfAllUsers[i].UserName </li>
    }
}

private Project projectItem { get; set; } = new Project();
private ApplicationUser AssignUser { get; set; } = new ApplicationUser();
private List<ApplicationUser> ListOfAllUsers { get; set; } = new List<ApplicationUser>();

//submit and create project with the assigned users
private async void CreateNewProject()
{
    projectItem.AssignedUsersToProject = ListOfAllUsers;

    try
    {
        var response = await Http.PostAsJsonAsync("Projects", projectItem);
        var content = await response.Content.ReadAsStringAsync();
        var project = JsonConvert.DeserializeObject<Project>(content);
       
        if(response.IsSuccessStatusCode)
            Navigation.NavigateTo($"/projects");

    }
    catch (Exception e)
    {

    }
}

// find and add user
private async void AddUserToProject()
{

    try
    {
        var response = await Http.PostAsJsonAsync($"Projects/{AssignUser.UserName}", AssignUser);
        var content = await response.Content.ReadAsStringAsync();
        var userobject = JsonConvert.DeserializeObject<ApplicationUser>(content);

        if (response.IsSuccessStatusCode)
        {
            if (!ListOfAllUsers.Any(n => n.UserName.Equals(userobject.UserName)))
            {
                ListOfAllUsers.Add(userobject);
            } else
                {
                    AssignUser.UserName = "This user is already added to the project.";
                }
        } else if (!response.IsSuccessStatusCode)
            {
                AssignUser.UserName = "User not found, try again";
            }
    }
    catch (Exception e)
    {

    }
}

控制器：创建项目

[HttpPost]
    public async Task<ActionResult<Project>> PostProject(Project project)
    {

        _context.Projects.Add(project);
        await _context.SaveChangesAsync(); // error occurs when reaching this point
        return CreatedAtAction("GetProject", new { id = project.ProjectId }, project);

    }

控制器：查找并返回用户

[HttpPost("{userEmail}")]
    public async Task<ActionResult<ApplicationUser>> AddUserToProject(string userEmail)
    {
        try
        {
            // Find user
            ApplicationUser userValid = _userManager.Users.Where
                (s => s.Email == userEmail).First();

            return userValid;
        }
        catch (InvalidOperationException)
        {
            return BadRequest();
        }
    }

型号

 public class Project
{
    [Key]
    public Guid ProjectId { get; set; }

    [Required]
    public string ProjectName { get; set; } 

    [JsonIgnore]
    public ICollection<ApplicationUser> AssignedUsersToProject { get; set; }

    public Company assignedCompanyForProject { get; set; }
}

public class ApplicationUser : IdentityUser
{
    public string firstName { get; set; }

    public string lastName { get; set; }

    [JsonIgnore]
    public ICollection<Project> Projects { get; set; }
}

表格图片

您键入要添加到项目中的用户的名称，然后单击“添加用户”，如果用户是存在的用户，它将查找并返回用户（这不会创建项目，但只会查找用户）。然后将该用户添加到 ListOfAllUsers 列表中，然后循环显示所有当前分配的用户。一旦在相关用户旁边给出了项目标题和描述，应按下“创建项目”按钮，这将使用已确定的分配用户创建整个项目。这是提交到数据库以添加新项目项的内容

建议的更改

实现 EntityState.Unchanged;

foreach(var x in project.AssignedUsersToProject)
        {
            _context.Entry(x).State = EntityState.Unchanged;
        }
            
        _context.Projects.Add(project);

导致以下错误：

ystem.Text.Json.JsonException: A possible object cycle was detected. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32

Answer 1

在创建项目时在控制器中实现以下解决了该问题。

foreach(var x in project.AssignedUsersToProject)
    {
        _context.Entry(x).State = EntityState.Unchanged;
    }
        
    _context.Projects.Add(project);