贪婪加载是指查询一个类型实体的时候同时查询与实体关联的类型
通过Include()方法实现
using (var context = new SchoolDBEntities())
{
var stud1 = (from s in context.Students.Include("Standard")
where s.StudentName == "Student1"
select s).FirstOrDefault<Student>();
}
using (var ctx = new SchoolDBEntities())
{
var stud1 = ctx.Students.Include("Standard")
.Where(s => s.StudentName == "Student1").FirstOrDefault<Student>(); }
SELECT TOP (1)
[Extent1].[StudentID] AS [StudentID],
[Extent1].[StudentName] AS [StudentName],
[Extent2].[StandardId] AS [StandardId],
[Extent2].[StandardName] AS [StandardName],
[Extent2].[Description] AS [Description]
FROM [dbo].[Student] AS [Extent1]
LEFT OUTER JOIN [dbo].[Standard] AS [Extent2] ON [Extent1].[StandardId] = [Extent2].[StandardId]
WHERE 'Student1' = [Extent1].[StudentName]
using System;
using System.Data.Entity; class Program
{
static void Main(string[] args)
{ using (var ctx = new SchoolDBEntities())
{
var stud1 = ctx.Students.Include(s => s.Standard)
.Where(s => s.StudentName == "Student1")
.FirstOrDefault<Student>(); }
}
}
SELECT TOP (1)
[Extent1].[StudentID] AS [StudentID],
[Extent1].[StudentName] AS [StudentName],
[Extent2].[StandardId] AS [StandardId],
[Extent2].[StandardName] AS [StandardName],
[Extent2].[Description] AS [Description]
FROM [dbo].[Student] AS [Extent1]
LEFT OUTER JOIN [dbo].[Standard] AS [Extent2] ON [Extent1].[StandardId] = [Extent2].[StandardId]
WHERE 'Student1' = [Extent1].[StudentName]
Load multiple levels of related entities:
using (var ctx = new SchoolDBEntities())
{
var stud1 = ctx.Students.Include("Standard.Teachers")
.Where(s => s.StudentName == "Student1")
.FirstOrDefault<Student>();
}
using (var ctx = new SchoolDBEntities())
{
var stud1 = ctx.Students.Include(s => s.Standard.Teachers)
.Where(s => s.StudentName == "Student1")
.FirstOrDefault<Student>();
}
SELECT [Project2].[StudentID] AS [StudentID],
[Project2].[StudentName] AS [StudentName],
[Project2].[StandardId] AS [StandardId],
[Project2].[StandardName] AS [StandardName],
[Project2].[Description] AS [Description],
[Project2].[C1] AS [C1],
[Project2].[TeacherId] AS [TeacherId],
[Project2].[TeacherName] AS [TeacherName],
[Project2].[StandardId1] AS [StandardId1]
FROM ( SELECT
[Limit1].[StudentID] AS [StudentID],
[Limit1].[StudentName] AS [StudentName],
[Limit1].[StandardId1] AS [StandardId],
[Limit1].[StandardName] AS [StandardName],
[Limit1].[Description] AS [Description],
[Project1].[TeacherId] AS [TeacherId],
[Project1].[TeacherName] AS [TeacherName],
[Project1].[StandardId] AS [StandardId1],
CASE WHEN ([Project1].[TeacherId] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
FROM (SELECT TOP (1) [Extent1].[StudentID] AS [StudentID], [Extent1].[StudentName] AS [StudentName], [Extent1].[StandardId] AS [StandardId2], [Extent2].[StandardId] AS [StandardId1], [Extent2].[StandardName] AS [StandardName], [Extent2].[Description] AS [Description]
FROM [dbo].[Student] AS [Extent1]
LEFT OUTER JOIN [dbo].[Standard] AS [Extent2] ON [Extent1].[StandardId] = [Extent2].[StandardId]
WHERE 'updated student' = [Extent1].[StudentName] ) AS [Limit1]
LEFT OUTER JOIN (SELECT
[Extent3].[TeacherId] AS [TeacherId],
[Extent3].[TeacherName] AS [TeacherName],
[Extent3].[StandardId] AS [StandardId]
FROM [dbo].[Teacher] AS [Extent3]
WHERE [Extent3].[StandardId] IS NOT NULL ) AS [Project1] ON [Limit1].[StandardId2] = [Project1].[StandardId]
) AS [Project2]
ORDER BY [Project2].[StudentID] ASC, [Project2].[StandardId] ASC, [Project2].[C1] ASC