Question

public class Newtask
{
    [Key]
    public int TId { get; set; }
    public string Name { get; set; }
    public int Estimated_days_of_work { get; set; }
    public virtual ICollection<Enrollment> Enrollments { get; set; }
    public virtual ICollection<Subtask> Subtasks { get; set; }
}

public class Subtask
{
    [Key]
    public int SId { get; set; }
    public string SubName { get; set; }
    public int SEstimated_days_of_work { get; set; }
    public int NewtaskTId { get; set; }
    public virtual Newtask Newtasks { get; set; } 
}

public class SubSubtask
{
    [Key]
    public int SsId { get; set; }
    public string SubSubTaskName { get; set; }
    public int SsEstimated_days_of_work { get; set; }
    public int NewtaskTId { get; set; }
    public int SId { get; set; }
    public virtual Newtask Newtasks { get; set; }
    public virtual Subtask Subtasks { get; set; }
}

现在我有这些类，我想显示它们之间的关系，就像每个任务都有子任务，而子任务也有其子任务，但是当我运行应用程序时，出现了以下错误：

System.Data.SqlClient.SqlException：'在表'SubSubtasks'上引入FOREIGN KEY约束'FK_dbo.SubSubtasks_dbo.Subtasks_SId'可能会导致循环或多个级联路径。指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY约束。无法创建约束或索引。请参阅先前的错误。'

如何修改这种关系？

Answer 1

您的类正在循环依赖，因此当您删除某些实体时，它将因多个错误而中断。如果忽略删除实体，则可以将其添加到dbcontext类的模型构建器中。

protected override void OnModelCreating(ModelBuilder modelbuilder)
{
foreach (var relationship in modelbuilder.Model.GetEntityTypes().SelectMany(e 
            => e.GetForeignKeys()))
{
    relationship.DeleteBehavior = DeleteBehavior.Restrict;
}

base.OnModelCreating(modelbuilder);
}

尽管正确的解决方案是更改不会循环依赖的业务模型。如果您没有发现任何问题，可以通过这种方式更改课程：

public class Newtask
{
    [Key]
    public int TId { get; set; }
    public string Name { get; set; }
    public int Estimated_days_of_work { get; set; }
    public virtual ICollection<Enrollment> Enrollments { get; set; }
    public virtual ICollection<Subtask> Subtasks { get; set; }
}

public class Subtask
{
    [Key]
    public int SId { get; set; }
    public string SubName { get; set; }
    public int SEstimated_days_of_work { get; set; }
    public int NewtaskTId { get; set; }
    public virtual Newtask Newtasks { get; set; } 
    public virtual Substask HasSubtask{get;set;}
}

，然后将dbset中的modelbuilder更改为：

modelbuilder.Entity(typeof (Subtask))
        .OnDelete(DeleteBehavior.Restrict);

我想显示与以下课程的关系，但出现这些错误

1 个答案: