使用实体框架核心指定处理两个联接表(以前处理多对多)的多对多

您可以“合并”该文件 ProjectProduct 和 ProjectProductOwner 坐在一张桌子上。既然你加了 Owners Project 首先,然后添加一个或多个 Products 每人 Owner 项目 我认为不需要第三个多对多实体,因此简化了一点:)

注意:我甚至没有为这个错误而烦恼,因为正如你所说的,我也同意,这些错误通常出现在你的模型不正确的时候。

物主

public class Owner
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<ProjectOwner> ProjectOwners { get; set; }
    public ICollection<ProjectProductOwner> ProjectProductOwners { get; set; }
}

Product

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<ProjectProductOwner> ProjectProductOwners { get; set; }
}

Project and many-to-many tables

public class Project
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<ProjectOwner> ProjectOwners { get; set; }
    public ICollection<ProjectProductOwner> ProjectProductOwners { get; set; }

    public Project()
    {
        ProjectOwners = new List<ProjectOwner>();
        ProjectProductOwners = new List<ProjectProductOwner>();
    }
}

public class ProjectOwner
{
    public int OwnerId { get; set; }
    public Owner Owner { get; set; }
    public int ProjectId { get; set; }
    public Project Project { get; set; }
}

public class ProjectProductOwner
{
    public int ProductId { get; set; }
    public Product Product { get; set; }
    public int OwnerId { get; set; }
    public Owner Owner { get; set; }
    public int ProjectId { get; set; }
    public Project Project { get; set; }
}

DbContext

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    // Configure Owners in a Project
    modelBuilder.Entity<ProjectOwner>()
        .HasKey(p => new { p.ProjectId, p.OwnerId });

    modelBuilder.Entity<ProjectOwner>()
        .HasOne(bc => bc.Project)
        .WithMany(b => b.ProjectOwners)
        .HasForeignKey(bc => bc.ProjectId);

    modelBuilder.Entity<ProjectOwner>()
        .HasOne(bc => bc.Owner)
        .WithMany(c => c.ProjectOwners)
        .HasForeignKey(bc => bc.OwnerId);

    // Configure Products for each owner in a Project
    modelBuilder.Entity<ProjectProductOwner>()
        .HasKey(p => new { p.ProjectId, p.ProductId, p.OwnerId });

    modelBuilder.Entity<ProjectProductOwner>()
        .HasOne(bc => bc.Project)
        .WithMany(b => b.ProjectProductOwners)
        .HasForeignKey(bc => bc.ProjectId);

    modelBuilder.Entity<ProjectProductOwner>()
        .HasOne(bc => bc.Product)
        .WithMany(c => c.ProjectProductOwners)
        .HasForeignKey(bc => bc.ProductId);

    modelBuilder.Entity<ProjectProductOwner>()
        .HasOne(bc => bc.Owner)
        .WithMany(c => c.ProjectProductOwners)
        .HasForeignKey(bc => bc.OwnerId);
}

最后,您可以添加新项目并使用以下内容进行查询:

using (var db = new ProjectContext())
{
    var project = new Project();
    project.Name = "My project";

    // assumes there's 3 owners and 2 products already inserted in the DB

    // Add the 3 owners to the project
    project.ProjectOwners.Add(new ProjectOwner { OwnerId = 1});
    project.ProjectOwners.Add(new ProjectOwner { OwnerId = 2});
    project.ProjectOwners.Add(new ProjectOwner { OwnerId = 3});

    // Add Product 1 to Owner 1 and 2
    project.ProjectProductOwners.Add(new ProjectProductOwner { ProductId = 1, OwnerId = 1 });
    project.ProjectProductOwners.Add(new ProjectProductOwner { ProductId = 1, OwnerId = 2 });

    // Add Product 2 to Owner 1 and 3
    project.ProjectProductOwners.Add(new ProjectProductOwner { ProductId = 2, OwnerId = 1 });
    project.ProjectProductOwners.Add(new ProjectProductOwner { ProductId = 2, OwnerId = 3 });

    db.Add(project);
    db.SaveChanges();

    var projects = db.Project
        .Include(p => p.ProjectOwners)
        .ThenInclude(p => p.Owner)
        .Include(p => p.ProjectProductOwners)
        .ThenInclude(p => p.Product)
        .FirstOrDefault();
}