LINQ to SQL:当“UpdateCheck = Never"时更新而不刷新

问题描述

我有一个 Account 实体，它包含UpdateCheck = Never"中的所有字段，只有一个字段除外.ModifiedTime"字段使用UpdateCheck=Always".目的是 – 并发检查应仅基于ModifiedTime"列.

出于测试目的，我提供了在 C# 代码中硬编码的ModifiedTime"值.因此不需要从数据库中获取任何值以进行并发.只有当我调用 Refresh 方法时，代码才会更新数据库.这看起来很奇怪.有什么方法可以避免这种情况吗?

请参阅:

无需先在 LINQ 2 中选择数据即可更新SQL?

LINQ to SQL 中的 UPDATE SELECT

linq to sql 更新多行

默认值(C# 变量)LINQ to SQL 更新中的问题

解决方案

感谢 @sgmoore .要更新的值在 Attach 方法之后设置.现在它正在工作.还有什么需要改进的吗?

生成的 SQL

更新 [dbo].[账户]SET [AccountType] = @p2, [Duration] = @p3, [ModifiedTime] = @p4WHERE ([AccountNumber] = @p0)AND ([ModifiedTime] = @p1)-- @p0: 输入整数 (大小 = -1; Prec = 0; 比例 = 0) [1]-- @p1:输入日期时间(大小 = -1；Prec = 0；比例 = 0)[6/25/2012 5:08:32 PM]-- @p2: 输入 NChar (Size = 10; Prec = 0; Scale = 0) [NEXT]-- @p3:输入整数(大小 = -1；Prec = 0；比例 = 0)[4]-- @p4:输入日期时间(大小 = -1；Prec = 0；比例 = 0)[6/26/2012 10:29:19 AM]-- 上下文:SqlProvider(Sql2008) 模型:AttributedMetaModel Build:4.0.30319.1

代码

 public void UpdateAccount(){//使用前一个选择的值DateTime previousDateTime = new DateTime(2012, 6, 25, 17, 8, 32, 677);RepositoryLayer.Account accEntity = new RepositoryLayer.Account();accEntity.AccountNumber = 1;//首要的关键accEntity.ModifiedTime = previousDateTime;//并发列accountRepository.UpdateChangesByAttach(accEntity);//Attach后要修改的值accEntity.AccountType = "NEXT";accEntity.ModifiedTime = DateTime.Now;accEntity.Duration = 4;accountRepository.SubmitChanges();}public virtual void UpdateChangesByAttach(T entity){if (Context.GetTable().GetOriginalEntityState(entity) == null){//如果还没有附加Context.GetTable().Attach(entity);}}

I have an Account entity which has all fields in "UpdateCheck = Never" except one field. The "ModifiedTime" field uses "UpdateCheck=Always". The intention is – concurrency check should be based on "ModifiedTime" column only.

For the test purpose I am supplying the "ModifiedTime" value hard coded in C# code. So there is no need to fetch any value from database for concurrency. Still the code will update the database only if I call for the Refresh method. This seems strange. Any approach to avoid this?

Refer: "Updating Without Querying" section in http://msdn.microsoft.com/en-us/library/bb386929.aspx

Note: I am trying to avoid the SELECT statement by not using Refresh

Generated SQL

 SELECT [t0].[AccountNumber], [t0].[AccountType], [t0].[Duration], [t0].[DepositedAmount], [t0].[Prefernce], [t0].[Comment], [t0].[ModifiedTime]
 FROM [dbo].[Account] AS [t0]
 WHERE [t0].[AccountNumber] = @p0

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1]
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1

Update Query

UPDATE [dbo].[Account]
SET [AccountType] = @p2, [Duration] = @p3
WHERE ([AccountNumber] = @p0)
AND ([ModifiedTime] = @p1)

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1]
-- @p1: Input DateTime (Size = -1; Prec = 0; Scale = 0) [6/25/2012 5:08:32 PM]
-- @p2: Input NChar (Size = 10; Prec = 0; Scale = 0) [SUCESS]
-- @p3: Input Int (Size = -1; Prec = 0; Scale = 0) [2]
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1

Table Structure

CREATE TABLE [dbo].[Account](
[AccountNumber] [int] NOT NULL,
[AccountType] [nchar](10) NOT NULL,
[Duration] [int] NOT NULL,
[DepositedAmount] [int] NULL,
[Prefernce] [int] NULL,
[Comment] [nvarchar](50) NULL,
[ModifiedTime] [datetime] NOT NULL,
 CONSTRAINT [PK_Account] PRIMARY KEY CLUSTERED
(
[AccountNumber] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF,   ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

C# Code

    public virtual void UpdateChangesByAttach(T entity)
    {

        if (Context.GetTable<T>().GetOriginalEntityState(entity) == null)
        {
            //If it is not already attached
            Context.GetTable<T>().Attach(entity);
            Context.Refresh(System.Data.Linq.RefreshMode.KeepCurrentValues, entity);
        }

    }

    public void UpdateAccount()
    {
        //Used value from previous select
        DateTime previousDateTime = new DateTime(2012, 6, 25, 17, 8, 32, 677);

        RepositoryLayer.Account accEntity = new RepositoryLayer.Account();
        accEntity.AccountNumber = 1;

        accEntity.AccountType = "SUCESS";
        accEntity.ModifiedTime = previousDateTime;
        accEntity.Duration = 2;

        accountRepository.UpdateChangesByAttach(accEntity);
        accountRepository.SubmitChanges();

    }

Table Data

READING:

1. LINQ to SQL: how to update the only field without retrieving whole entity

2. Update without first selecting data in LINQ 2 SQL?

3. UPDATE SELECT in LINQ to SQL

4. linq to sql update mulitple rows

5. Default Values (of C# variables) Issue in LINQ to SQL Update

---

解决方案

Thanks to @sgmoore . The values to be updated are set after the Attach method. Now it is working. Is there anything yet to improve?

Generated SQL

UPDATE [dbo].[Account]
SET [AccountType] = @p2, [Duration] = @p3, [ModifiedTime] = @p4
WHERE ([AccountNumber] = @p0)
      AND ([ModifiedTime] = @p1)

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1]
-- @p1: Input DateTime (Size = -1; Prec = 0; Scale = 0) [6/25/2012 5:08:32 PM]
-- @p2: Input NChar (Size = 10; Prec = 0; Scale = 0) [NEXT]
-- @p3: Input Int (Size = -1; Prec = 0; Scale = 0) [4]
-- @p4: Input DateTime (Size = -1; Prec = 0; Scale = 0) [6/26/2012 10:29:19 AM]
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1

CODE

    public void UpdateAccount()
    {
        //Used value from previous select
        DateTime previousDateTime = new DateTime(2012, 6, 25, 17, 8, 32, 677);

        RepositoryLayer.Account accEntity = new RepositoryLayer.Account();
        accEntity.AccountNumber = 1; //Primary Key
        accEntity.ModifiedTime = previousDateTime; //Concurrency column

        accountRepository.UpdateChangesByAttach(accEntity);

        //Values to be modified after Attach
        accEntity.AccountType = "NEXT";
        accEntity.ModifiedTime = DateTime.Now;
        accEntity.Duration = 4;

        accountRepository.SubmitChanges();

    }

    public virtual void UpdateChangesByAttach(T entity)
    {

        if (Context.GetTable<T>().GetOriginalEntityState(entity) == null)
        {
            //If it is not already attached
            Context.GetTable<T>().Attach(entity);
        }

    }

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