前言:本来要使用实体拆分实现一对一,但发现查询时无法单独查询,影响效率,故改用手动建立一对一关系
例:
实体类:
public class TestDbContext : DbContext { public DbSet<Test> Tests { get; set; } public DbSet<TestUnitPrice> TestUnitPrices { get; set; } public TestDbContext() : base() { } protected override void OnModelCreating(DbModelBuilder modelBuilder) { //base.OnModelCreating(modelBuilder); //一对一关系中,依赖对象的主键与外键会被修改为同一个,所以在此要再次设置一下依赖对象的主键 modelBuilder.Entity<TestUnitPrice>().HasKey(t => t.ID); //设置主体对象 modelBuilder.Entity<Test>().HasRequired(t => t.UnitPrice).WithRequiredPrincipal(); } } public class Test { public long ID { get; set; } public string Name { get; set; } public string Remarks { get; set; } //导航属性 public virtual TestUnitPrice UnitPrice { get; set; } } public class TestUnitPrice { public long ID { get; set; } public decimal UnitPrice { get; set; } public string Remarks { get; set; } }
对应的数据库为:
添加数据:(主体记录与依赖记录的 ID 将自动设置为相同值)
TestDbContext db = new TestDbContext(); //添加对象,记得同时添加依赖对象 db.Tests.Add(new Test() { Name = "测试1", Remarks = "测试1备注", UnitPrice = new TestUnitPrice() { UnitPrice = 10, Remarks = "测试1单价备注" } }); db.SaveChanges();
此时将生成两条SQL语句:
exec sp_executesql N‘INSERT [dbo].[Tests]([Name], [Remarks]) VALUES (@0, @1) SELECT [ID] FROM [dbo].[Tests] WHERE @@ROWCOUNT > 0 AND [ID] = scope_identity()‘,N‘@0 nvarchar(max) ,@1 nvarchar(max) ‘,@0=N‘测试1‘,@1=N‘测试1备注‘
exec sp_executesql N‘INSERT [dbo].[TestUnitPrices]([ID], [UnitPrice], [Remarks]) VALUES (@0, @1, @2) ‘,N‘@0 bigint,@1 decimal(18,2),@2 nvarchar(max) ‘,@0=2,@1=10.00,@2=N‘测试1单价备注‘
同时更新主体和依赖数据:
TestDbContext db = new TestDbContext(); var test = db.Tests.Find(1); test.Remarks = "更新主实体字段01"; test.UnitPrice.Remarks = "更新依赖实体字段01"; db.SaveChanges();
此时将生产四条SQL语句,两条查询,两条更新
exec sp_executesql N‘SELECT TOP (2) [Extent1].[ID] AS [ID], [Extent1].[Name] AS [Name], [Extent1].[Remarks] AS [Remarks] FROM [dbo].[Tests] AS [Extent1] WHERE [Extent1].[ID] = @p0‘,N‘@p0 int‘,@p0=1
exec sp_executesql N‘SELECT [Extent1].[ID] AS [ID], [Extent1].[UnitPrice] AS [UnitPrice], [Extent1].[Remarks] AS [Remarks] FROM [dbo].[TestUnitPrices] AS [Extent1] WHERE [Extent1].[ID] = @EntityKeyValue1‘,N‘@EntityKeyValue1 bigint‘,@EntityKeyValue1=1
exec sp_executesql N‘UPDATE [dbo].[Tests] SET [Remarks] = @0 WHERE ([ID] = @1) ‘,N‘@0 nvarchar(max) ,@1 bigint‘,@0=N‘更新主实体字段01‘,@1=1
exec sp_executesql N‘UPDATE [dbo].[TestUnitPrices] SET [Remarks] = @0 WHERE ([ID] = @1) ‘,N‘@0 nvarchar(max) ,@1 bigint‘,@0=N‘更新依赖实体字段01‘,@1=1
单独更新主体数据:
TestDbContext db = new TestDbContext(); var test = db.Tests.Find(1); test.Remarks = "更新主实体字段1"; db.SaveChanges();
SQL:
exec sp_executesql N‘SELECT TOP (2) [Extent1].[ID] AS [ID], [Extent1].[Name] AS [Name], [Extent1].[Remarks] AS [Remarks] FROM [dbo].[Tests] AS [Extent1] WHERE [Extent1].[ID] = @p0‘,N‘@p0 int‘,@p0=1
exec sp_executesql N‘UPDATE [dbo].[Tests] SET [Remarks] = @0 WHERE ([ID] = @1) ‘,N‘@0 nvarchar(max) ,@1 bigint‘,@0=N‘更新主实体字段1‘,@1=1
单独更新依赖数据:
TestDbContext db = new TestDbContext(); var test = db.TestUnitPrices.Find(1); test.Remarks = "更新依赖实体字段1"; db.SaveChanges();
SQL:
exec sp_executesql N‘SELECT TOP (2) [Extent1].[ID] AS [ID], [Extent1].[UnitPrice] AS [UnitPrice], [Extent1].[Remarks] AS [Remarks] FROM [dbo].[TestUnitPrices] AS [Extent1] WHERE [Extent1].[ID] = @p0‘,N‘@p0 int‘,@p0=1
exec sp_executesql N‘UPDATE [dbo].[TestUnitPrices] SET [Remarks] = @0 WHERE ([ID] = @1) ‘,N‘@0 nvarchar(max) ,@1 bigint‘,@0=N‘更新依赖实体字段1‘,@1=1
简单查询与删除
TestDbContext db = new TestDbContext(); var test = db.Tests.Include("UnitPrice").First(t => t.ID == 3); db.Tests.Remove(test); db.SaveChanges();
原文:http://www.cnblogs.com/gmcn/p/7118932.html