Question

在Entity Framework中的LINQ查询中使用AsNoTracking方法时，是否应该针对每个表或整个查询使用它以禁用整个查询的更改跟踪？

1。针对整个查询

var query = (from t1 in db.Table1
            from t2 in db.Table2.Where(o => t1.ConditionId == o.ConditionId)
            select t1).AsNoTracking()

2。针对每个表格

var query = (from t1 in db.Table1.AsNoTracking()
            from t2 in db.Table2.AsNoTracking().Where(o => t1.ConditionId == o.ConditionId)
            select t1)

我的目的是禁用整个查询的更改跟踪，但如果不需要，则不希望对每个表使用它。

MSDN引用此方法的文档中的查询对象：

此方法通过调用底层的AsNoTracking方法来工作查询对象。如果基础查询对象没有 AsNoTracking方法，然后调用此方法将不执行任何操作。

Answer 1

基于测试我刚刚做出两个结果是一样的。使用Table Level或QueryLevel AsNoTracking导致没有实体被保留到ChangeTracker中。但不管怎样，Table2中的实体永远不会放在ChangeTracker中，正如你在WithtoutAsNoTracking测试中看到的那样。

基于这个假设，您确实在查询t1和t2中的数据。当我查询所有条目仍然添加到查询中的单个AsNoTracking时，我添加了一个测试，没有跟踪任何条目。如果将AsNoTracking（）直接放在table1上，则不会跟踪table1和table2中的实体。

    [TestMethod]
    public void QueryLevelAsNoTracking()
    {
        using (var context = new DbContext())
        {
            var query = (from t1 in context.Table1
                         from t2 in context.Table2.Where(o => t1.ConditionId == o.ConditionId)
                         select t1).AsNoTracking();

            var list = query.ToList();
            Assert.AreEqual(0, context.ChangeTracker.Entries().Count());
        }
    }

    [TestMethod]
    public void TableLevelAsNoTracking()
    {
        using (var context = new DbContext())
        {
            var query = (from t1 in context.Table1.AsNoTracking()
                         from t2 in context.Table2.Where(o => t1.ConditionId == o.ConditionId)
                         select t1);

            var list = query.ToList();
            Assert.AreEqual(0, context.ChangeTracker.Entries().Count());
        }
    }

    [TestMethod]
    public void WithtoutAsNoTracking()
    {
        using (var context = new DbContext())
        {
            var query = (from t1 in context.Table1
                         from t2 in context.Table2.Where(o => t1.ConditionId == o.ConditionId)
                         select t1);

            var list = query.ToList();
            Assert.AreEqual(7, context.ChangeTracker.Entries().Count(x => x.Entity is Table1));
            Assert.AreEqual(0, context.ChangeTracker.Entries().Count(x => x.Entity is Table2));
        }
    }


    [TestMethod]
    public void QueryLevelAsNoTracking_SelectAllData()
    {
        using (var context = new DbContext())
        {
            var query = (from t1 in context.Table1
                         from t2 in context.Table2.Where(o => t1.ConditionId == o.ConditionId)
                         select new
                                    {
                                            t1,
                                            t2
                                    }).AsNoTracking();

            var list = query.ToList();
            Assert.AreEqual(0, context.ChangeTracker.Entries().Count());
        }
    }

    [TestMethod]
    public void Table1AsNoTracking_SelectAllData()
    {
        using (var context = new DbContext())
        {
            var query = (from t1 in context.Table1.AsNoTracking()
                         from t2 in context.Table2.Where(o => t1.ConditionId == o.ConditionId)
                         select new
                         {
                             t1,
                             t2
                         });

            var list = query.ToList();
            Assert.AreEqual(0, context.ChangeTracker.Entries().Count(x => x.Entity is Table1));
            Assert.AreEqual(0, context.ChangeTracker.Entries().Count(x => x.Entity is Table2));
        }
    }

另外，我在join子句中删除了AsNoTracking From Table2，因为它导致了异常。

System.ArgumentException：方法'System.Data.Entity.Infrastructure.DbQuery 1[DataModel.Table12 AsNoTracking()' declared on type 'System.Data.Entity.Infrastructure.DbQuery 1 [DataModel.Table2]'无法使用类型'System.Data.Objects.ObjectQuery`1 [DataModel]的实例调用。表2]'

实体框架中LINQ查询中的AsNoTracking的范围

1 个答案: