实体框架：使用现有数据（种子）填充多对多关系

Posted 2021-04-03

在我的Code-First数据库中，我在对象“Question”和对象“Section”之间存在多对多关系，如下所示：在Section：

public List<Question> Questions { get; set; }

问题：

public List<Section> Sections { get; set; }

这确实在两者之间创建了一个名为QuestionSections的链接表。但是，当我尝试运行我的种子方法时，链接表不会被填充。

种子方法代码的相关部分如下：

var Sections = new List<Section>
{
    new Section
    {
        InternalSectionId = 1,
        Name = "Global information",
        SurveyId = context.Surveys.First(s => s.Title == "Test Survey").Id
    },
    new Section
    {
        InternalSectionId = 2,
        Name = "More specific",
        SurveyId = context.Surveys.First(s => s.Title == "Test Survey").Id
    },
    new Section
    {
        InternalSectionId = 3,
        Name = "TestingSection",
        SurveyId = context.Surveys.First(s => s.Title == "Test Survey").Id
    }
};
Sections.ForEach(x => context.Sections.AddOrUpdate(ss => ss.Name, x));
context.SaveChanges();

List<Section> section1 = context.Sections.Where(sect => sect.InternalSectionId == 1 && sect.SurveyId == 1)
    .ToList();
List<Section> section2 = context.Sections.Where(sect => sect.InternalSectionId == 2 && sect.SurveyId == 1)
    .ToList();
List<Section> section3 = context.Sections.Where(sect => sect.InternalSectionId == 3 && sect.SurveyId == 1)
    .ToList();

var questions = new List<Question>
            {
                new Question
                {
                    Sections = section1,
                    Title = "What is 1+1?",
                    QuestionOrderId = 1,
                    AnswerRequired = true,
                    InputTypeId = context.InputTypes.First(ip => ip.VisibleName.Equals("Dropdownbox")).Id,
                    StorageType = (int)Constants.Constants.StorageTypes.BoolType
                },
                new Question
                {
                    Sections = section2,
                    Title = "What is 2/1?",
                    QuestionOrderId = 1,
                    AnswerRequired = true,
                    InputTypeId = context.InputTypes.First(ip => ip.VisibleName.Equals("Text")).Id,
                    StorageType = (int)Constants.Constants.StorageTypes.IntType
                    }
                }
            }
questions.ForEach(x => context.Questions.AddOrUpdate(q => q.Title, x));
context.Configuration.ValidateOnSaveEnabled = false;
context.SaveChanges();

创建问题，创建部分，但不填充链接表。我已经检查了对象section1，section2和section3是否已启动并填充，它们是。

我究竟做错了什么？

答案

您还必须将类似的代码写入Link表。 questions.ForEach(x => context.Questions.AddOrUpdate(q => q.Title, x));因为当你调用context.SaveChanges();时DBContext不知道这个链接表。