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
<小时>
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:
LINQ to SQL: how to update the only field without retrieving whole entity
Update without first selecting data in LINQ 2 SQL?
UPDATE SELECT in LINQ to SQL
linq to sql update mulitple rows
Default Values (of C# variables) Issue in LINQ to SQL Update
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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