Entity Framework DbContext 新增、修改、刪除、查詢

namespace ConsoleApplication1.Models
{
    using System.Data.Entity;
public class DemoContext : DbContext
{
    public DbSet<Topic> Topic { get; set; }
    public DbSet<Reply> Reply { get; set; }
}

}

namespace ConsoleApplication1.Models
{
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
[Table("Topic")]
public class Topic
{
    [Key]
    public int TopicId { get; set; }
    public string TopicTitle { get; set; }
    public virtual ICollection<Reply> Reply { get; set; }
}

}

namespace ConsoleApplication1.Models
{
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
[Table("Reply")]
public class Reply
{
    [Key]
    public int ReplyId { get; set; }
    [ForeignKey("Topic")]
    public int TopicId { get; set; }
    public string ReplyMessage { get; set; }
    public virtual Topic Topic { get; set; }
}

}

namespace ConsoleApplication1
{
    using ConsoleApplication1.Models;
    using System.Collections.Generic;
    using System.Data.Entity;
    using System.Linq;
class Program
{
    static void Main(string[] args)
    {
        // 初始化資料庫
        Database.SetInitializer(new DropCreateDatabaseAlways<DemoContext>());
        using (DemoContext db = new DemoContext())
        {
            db.Database.Initialize(false);
        }

        // 新增
        using (DemoContext db = new DemoContext())
        {
            db.Topic.Add(new Topic
            {
                TopicTitle = "a",
                Reply = new List<Reply>
                {
                    new Reply { ReplyMessage = "a1" },
                    new Reply { ReplyMessage = "a2" },
                    new Reply { ReplyMessage = "a3" },
                }
            });

            db.SaveChanges();
        }

        // 修改
        using (DemoContext db = new DemoContext())
        {
            var model = db.Topic.FirstOrDefault();
            if (model != null)
            {
                model.TopicTitle = "modify";
                db.SaveChanges();
            }
        }

        // 查詢
        using (DemoContext db = new DemoContext())
        {
            var model1 = db.Topic.Find(1);
            var model2 = db.Topic.SingleOrDefault();
            var model3 = db.Topic.FirstOrDefault();
        }

        // 刪除
        using (DemoContext db = new DemoContext())
        {
            var model = new Topic { TopicId = 1 };
            db.Entry(model).State = EntityState.Deleted;
            db.SaveChanges();
        }
    }
}

}

exec sp_reset_connection
go
exec sp_executesql N'INSERT [dbo].[Topic]([TopicTitle])
VALUES (@0)
SELECT [TopicId]
FROM [dbo].[Topic]
WHERE @@ROWCOUNT > 0 AND [TopicId] = scope_identity()',N'@0 nvarchar(max) ',@0=N'a'
go
exec sp_executesql N'INSERT [dbo].[Reply]([TopicId], [ReplyMessage])
VALUES (@0, @1)
SELECT [ReplyId]
FROM [dbo].[Reply]
WHERE @@ROWCOUNT > 0 AND [ReplyId] = scope_identity()',N'@0 int,@1 nvarchar(max) ',@0=1,@1=N'a1'
go
exec sp_executesql N'INSERT [dbo].[Reply]([TopicId], [ReplyMessage])
VALUES (@0, @1)
SELECT [ReplyId]
FROM [dbo].[Reply]
WHERE @@ROWCOUNT > 0 AND [ReplyId] = scope_identity()',N'@0 int,@1 nvarchar(max) ',@0=1,@1=N'a2'
go
exec sp_executesql N'INSERT [dbo].[Reply]([TopicId], [ReplyMessage])
VALUES (@0, @1)
SELECT [ReplyId]
FROM [dbo].[Reply]
WHERE @@ROWCOUNT > 0 AND [ReplyId] = scope_identity()',N'@0 int,@1 nvarchar(max) ',@0=1,@1=N'a3'
go

exec sp_reset_connection
go
SELECT TOP (1) 
    [c].[TopicId] AS [TopicId], 
    [c].[TopicTitle] AS [TopicTitle]
    FROM [dbo].[Topic] AS [c]
go
exec sp_reset_connection
go
exec sp_executesql N'UPDATE [dbo].[Topic]
SET [TopicTitle] = @0
WHERE ([TopicId] = @1)
',N'@0 nvarchar(max) ,@1 int',@0=N'modify',@1=1
go

exec sp_reset_connection
go
exec sp_executesql N'SELECT TOP (2) 
    [Extent1].[TopicId] AS [TopicId], 
    [Extent1].[TopicTitle] AS [TopicTitle]
    FROM [dbo].[Topic] AS [Extent1]
    WHERE [Extent1].[TopicId] = @p0',N'@p0 int',@p0=1
go
exec sp_reset_connection
go
SELECT TOP (2) 
    [c].[TopicId] AS [TopicId], 
    [c].[TopicTitle] AS [TopicTitle]
    FROM [dbo].[Topic] AS [c]
go
exec sp_reset_connection
go
SELECT TOP (1) 
    [c].[TopicId] AS [TopicId], 
    [c].[TopicTitle] AS [TopicTitle]
    FROM [dbo].[Topic] AS [c]
go

exec sp_reset_connection
go
exec sp_executesql N'DELETE [dbo].[Topic]
WHERE ([TopicId] = @0)',N'@0 int',@0=1
go