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我试图让对象的Studies属性Department延迟加载，但它只会在我急切加载时加载。我已经在没有结果DepartmentId的类中添加了 a ，Studyused和. 公共和私人二传手似乎没有区别（也不应该）。似乎没有任何效果。使用 EF 6.1。ICollectionISetvirtual

public class Department
{
  private Department() {}

  public Department(DepartmentTitle title)
  {
    if (title == null) throw new ArgumentNullException();

    this.Title = title;
    this.Studies = new HashSet<Study>();
  }

  public int DepartmentId { get; private set; }

  public virtual DepartmentTitle Title { get; private set; }
  public virtual ICollection<Study> Studies { get; set; }
}

public class Study
{
  private Study() {}

  public Study(StudyTitle title, Department department)
  {
    if (title == null) throw new ArgumentNullException();
    if (department == null) throw new ArgumentNullException();

    this.Title = title;
    this.Department = department;
  }

  public int StudyId { get; private set; }

  public virtual StudyTitle Title { get; private set; }
  public virtual Department Department { get; set; }
}

// Here I save the department and study objects
// I verified they exist in the database    
var department = new Department(new DepartmentTitle("Department Title Here"));
department.Studies.Add(new Study(new StudyTitle("Study Title Here"), department));
data.SaveChanges();

// In a new database context
// Here I try to lazy load the Studies property, but get null
// It works if I add Include("Studies") before Where()
Department department = data.Departments.Where(d => d.Title.Value == "Department Title Here").Single();
System.Console.WriteLine(department.Studies.First().Title.Value);

// DepartmentTitle and StudyTitle are simple complex types with a Value property
4

2 回答 2

2

您的 Study 类需要一个公共或受保护的无参数构造函数来处理延迟加载：MSDN

于 2014-04-28T06:07:24.747 回答
1

您需要实际加载研究：

department.Studies.Load();
System.Console.WriteLine(department.Studies.First().Title.Value);

否则它们将不存在并First()会崩溃。

因此，要么您是您Include()的实体以进行急切加载，要么您Load()稍后以一种懒惰的方式。

于 2014-04-28T08:47:09.700 回答