实体框架未更新

Question

有时实体没有在 scope 内更新，但插入已提交。 我认为这个问题是由于隔离级别，添加到注册表中的查询数量。 我还认为这可能是数据库中事物有效的顺序，因为暗示更改实体的端点调用发生得非常快，即使顺序正确也是如此。 我不知道...

代码是这样的：

using (var scope = new TransactionScope())
{
     var db = new Context().Database.ExecuteSqlCommand("SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;")

     var student= db.Students.SingleOrDefault(x => x.ID == 1);

     var schoolName = "TestSchool";

     db.School.Insert(new School{ Name = schoolName }); // IT ALWAYS WORKS

     student.School = schoolName; //SOMETIMES THIS CHANGE DOESN'T WORK

     db.Save();

     scope.Complete();
}

有什么帮助吗？

它只发生在海量数据中，使测试变得困难

Answer 1

你应该做的是先查询学校，然后将结果分配给student.School

像这样：

using (var scope = new TransactionScope())
{
     var db = new Context().Database.ExecuteSqlCommand("SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;")

     var student= db.Students.SingleOrDefault(x => x.ID == 1);

     var schoolName = "TestSchool";

     db.School.Insert(new School{ Name = schoolName }); // IT ALWAYS WORKS

     // Query new school here
     var newSchool = db.School.SingleOrDefault(x => x.SchoolName = schoolName);
     // Assign the result to student's School property
     student.School = newSchool;

     db.Save();

     scope.Complete();
}

这样，实体框架将能够“跟踪”更改并生成正确的 SQL 以更新数据库