c# - Entity Framework 添加了许多实体，嵌套属性已经存在

Question

我需要一次添加很多实体。这并不复杂:

EntityType entities = GetEntities();
dbContext.MyTable.AddRange(entities);

但是每个实体引用另一个子属性(已经存在，并且我知道它的 ID)。有没有一种有效的方法可以避免提前查询所有子属性？

for (int i = 0; i < entities.Length; i++)
{
    // adding already existing property 
    entities[i].MyProperty = new MyProperty { Id = ExternalIds[i] };
}

dbContext.MyTable.AddRange(entities); // Don't want to create new entities

Answer 1

您可以创建仅包含 id 的空实体对象，您也可以将属性键添加到您的实体

public class Course
{
  public int CourseID { get; set; }
  public string Title { get; set; }
  public int Credits { get; set; }
  public int DepartmentID { get; set; }
  public virtual Department Department { get; set; }
}

在这里，您可以只输入 DepartmentID 值并保存，或者

Course.Department = new Department{ id = 123 }

docs says

If the reference is in the added state (in this example, the course object), the reference navigation property will not be synchronized with the key values of a new object until SaveChanges is called.