我被这个问题难住了。我试图实现的行为是让一个测试分配多个允许的学生组。这工作正常,但是当我尝试将同一组分配给多个测试时,它被移动而不是添加。我认为图片最能说明问题。
这是我的模型:
public class TestParameters
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
[DefaultValue(60)]
//in minutes
//0 = no limit
[DisplayName("Time Limit")]
public int TimeLimit { get; set; }
[Required]
[DefaultValue(10)]
[DisplayName("Number of Questions")]
public int NumQuestions { get; set; }
[Required]
[DisplayName("Open From")]
public DateTime OpenFrom { get; set; }
[DisplayName("Open To")]
public DateTime OpenTo { get; set; }
[DisplayName("Allowed Groups")]
public virtual ICollection<StudentGroup> AllowedGroups { get; set; }
}
public class StudentGroup
{
[Required]
[Key]
public string Code { get; set; }
[Required]
public string Name { get; set; }
public string Description { get; set; }
}
以及相关的控制者:
[HttpPost]
public ActionResult NewGroup()
{
var groupCode = Request["groupCode"];
var paramId = Request["parametersId"];
var group = db.StudentGroups.Find(groupCode);
var parameters = db.TestParameters.Find(int.Parse(paramId));
if (group == null)
{
ViewBag.ErrorMessage = "No group with code " + groupCode + " exists.";
}
else if (parameters.AllowedGroups.Contains(group))
{
ViewBag.ErrorMessage = "The group with code " + groupCode + " already has access to this test.";
}
else
{
parameters.AllowedGroups.Add(group);
db.SaveChanges();
}
return View(parameters);
}
什么会导致这种行为?
最佳答案
看起来你建立的是一对多关系,而不是你描述的你需要的多对多关系。
您在 DbContext OnModelCreating 中需要这样的东西:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<TestParameters>()
.HasMany(x => x.StudentGroup)
.WithMany(x => x.TestParameters)
.Map(x =>
{
x.ToTable("StudentGroupTestParameter")
x.MapLeftKey("Id");
x.MapRightKey("Code");
});
}
关于c# - 实体被移动而不是添加,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29904470/