public class AppContext : DbContext
{
public AppContext()
{
Configuration.LazyLoadingEnabled = true;
}
public virtual DbSet<AccountType> AccountTypes { get; set; }
}
public class AccountType
{
public Guid Id { get; set; }
public string Name { get; set; }
public virtual ICollection<AccountCode> AccountCodes { get; set; }
}
public class AccountCode
{
public Guid Id { get; set; }
public string Name { get; set; }
public Guid AccountTypeId { get; set; }
public virtual AccountType AccountType { get; set; }
}
在导航属性上使用virtual关键字可以启用延迟加载机制,但必须启用配置的LazyLoadingEnabled属性。
在AccountType :: AccountCodes导航属性上使用virtual关键字将在程序访问该属性时,只要db上下文仍然活动,即会加载所有帐户代码。
using (var context = new AppContext())
{
var accountType = context.AccountTypes.FirstOrDefault();
var accountCodes = accountType.AccountCodes;
}
派生的DbContext类中的虚拟关键字(虚拟DbSet <>)用于测试目的(模拟DbSet属性),但在此情况下,虚拟关键字与延迟加载无关。
===== 更新 =====
通常,我们会针对服务/逻辑进行测试,例如我们有另一层帐户类型服务如下。该服务通过构造函数使用某种依赖注入接受DbContext实例。
public class AccountTypeService
{
public AppContext _context;
public AccountTypeService(AppContext context)
{
_context = context;
}
public AccountType AddAccountType(string name)
{
var accountType = new AccountType { Id = Guid.NewGuid(), Name = name };
_context.AccountTypes.Add(accountType);
_context.SaveChanges();
return accountType;
}
}
现在我们需要测试账户类型服务,在这种情况下,我使用了mstest和automoq来创建模拟类。
[TestClass]
public class AccountTypeServiceTest
{
[TestMethod]
public void AddAccountType_NormalTest()
{
var accountTypes = new List<AccountType>();
var accountTypeSetMock = new Mock<DbSet<AccountType>>();
accountTypeSetMock.Setup(m => m.Add(It.IsAny<AccountType>())).Callback<AccountType>(accountType => accountTypes.Add(accountType));
var appContextMock = new Mock<AppContext>();
appContextMock.Setup(m => m.AccountTypes).Returns(accountTypeSetMock.Object);
var target = new AccountTypeService(appContextMock.Object);
var newAccountType = target.AddAccountType("test");
accountTypeSetMock.Verify(m => m.Add(It.IsAny<AccountType>()), Times.Once());
appContextMock.Verify(m => m.SaveChanges(), Times.Once());
Assert.AreEqual(1, accountTypes.Count);
Assert.IsNotNull(newAccountType);
Assert.AreNotEqual(Guid.Empty, newAccountType.Id);
Assert.AreEqual("test", newAccountType.Name);
}
}