同步DataContext，解决linq to sql更新数据的问题

ling to sql更新实体非常费劲！
一般网上的例子中都是这样的。

Customer cust = db.Customers.First(c => c.CustomerID == "ALFKI");
cust.ContactTitle = "Vice President";
db.SubmitChanges();

但是，貌似在分层系统中，数据库操作会写到数据访问层，定义实体，抽象出接口。

实体类

/// <summary>
/// 计划任务
/// </summary>
[Table(Name = "EDM_TaskPlan")]
public class TaskPlan
{
    /// <summary>
    /// 计划编码
    /// </summary>
    [Column(IsDbGenerated=true,IsPrimaryKey=true,Name="PlanID")]
    public int PlanID { get; set; }

    /// <summary>
    /// 任务名称
    /// </summary>
    [Column(Name="PlanName")]
    public string Name { get; set; }

    /// <summary>
    /// 任务描述
    /// </summary>
    [Column]
    public string Description { get; set; }

    /// <summary>
    /// 星期一定义
    /// </summary>
    [Column]
    public string MondayDef { get; set; }

    /// <summary>
    /// 星期二定义
    /// </summary>
    [Column]
    public string TuesdayDef { get; set; }

    /// <summary>
    /// 星期三定义
    /// </summary>
    [Column]
    public string WednesdayDef { get; set; }

    /// <summary>
    /// 星期四定义
    /// </summary>
    [Column]
    public string ThursdayDef { get; set; }

    /// <summary>
    /// 星期五定义
    /// </summary>
    [Column]
    public string FridayDef { get; set; }

    /// <summary>
    /// 星期六定义
    /// </summary>
    [Column]
    public string SaturdayDef { get; set; }

    /// <summary>
    /// 星期日定义
    /// </summary>
    [Column]
    public string SundayDef { get; set; }
}

    /// <summary>
/// 计划任务
/// </summary>
[Table(Name = "EDM_TaskPlan")]
public class TaskPlan
{
/// <summary>
/// 计划编码
/// </summary>
[Column(IsDbGenerated=true,IsPrimaryKey=true,Name="PlanID")]
public int PlanID { get; set; }
/// <summary>
/// 任务名称
/// </summary>
[Column(Name="PlanName")]
public string Name { get; set; }
/// <summary>
/// 任务描述
/// </summary>
[Column]
public string Description { get; set; }
/// <summary>
/// 星期一定义
/// </summary>
[Column]
public string MondayDef { get; set; }
/// <summary>
/// 星期二定义
/// </summary>
[Column]
public string TuesdayDef { get; set; }
/// <summary>
/// 星期三定义
/// </summary>
[Column]
public string WednesdayDef { get; set; }
/// <summary>
/// 星期四定义
/// </summary>
[Column]
public string ThursdayDef { get; set; }
/// <summary>
/// 星期五定义
/// </summary>
[Column]
public string FridayDef { get; set; }
/// <summary>
/// 星期六定义
/// </summary>
[Column]
public string SaturdayDef { get; set; }
/// <summary>
/// 星期日定义
/// </summary>
[Column]
public string SundayDef { get; set; }
}

数据访问接口

/// <summary>
/// 任务计划数据访问接口
/// </summary>
public interface ITaskPlanDao
{
    /// <summary>
    /// 查找全部
    /// </summary>
    /// <returns></returns>
    TaskPlan[] FindAll();

    /// <summary>
    /// 根据编码查找
    /// </summary>
    /// <param name="id">计划任务编码</param>
    /// <returns></returns>
    TaskPlan FindByID(int id);

    /// <summary>
    /// 保存或更新
    /// </summary>
    /// <param name="taskPlan">任务计划对象</param>
    /// <returns></returns>
    int SaveOrUpdate(TaskPlan taskPlan);

    /// <summary>
    /// 根据编码删除
    /// </summary>
    /// <param name="id">任务计划编码</param>
    /// <returns></returns>
    void DeleteByID(int id);
}

    /// <summary>
/// 任务计划数据访问接口
/// </summary>
public interface ITaskPlanDao
{
/// <summary>
/// 查找全部
/// </summary>
/// <returns></returns>
TaskPlan[] FindAll();
/// <summary>
/// 根据编码查找
/// </summary>
/// <param name="id">计划任务编码</param>
/// <returns></returns>
TaskPlan FindByID(int id);
/// <summary>
/// 保存或更新
/// </summary>
/// <param name="taskPlan">任务计划对象</param>
/// <returns></returns>
int SaveOrUpdate(TaskPlan taskPlan);
/// <summary>
/// 根据编码删除
/// </summary>
/// <param name="id">任务计划编码</param>
/// <returns></returns>
void DeleteByID(int id);
}

但是我在更新的时候出现了问题。

dbContext.Attach(taskPlan);
//根本不会更新
dbContext.Attach(taskPlan,true);
//An entity can only be attached as modified without original state if it //declares a version member or does not have an update check policy
dbContext.Attach(taskPlan,this.FindByID(taskPlan.PlanID));
//Cannot add an entity with a key that is already in use.

dbContext.Attach(taskPlan);
//根本不会更新
dbContext.Attach(taskPlan,true);
//An entity can only be attached as modified without original state if it //declares a version member or does not have an update check policy
dbContext.Attach(taskPlan,this.FindByID(taskPlan.PlanID));
//Cannot add an entity with a key that is already in use.

网上也有解决方案，就是加IsVersion字段，感觉怪怪的。所以我认命了，MS让我怎么办我就怎么办，我让一个Request共用一个DataContext实例。

ASP.NET MVC + EntLib4 + LinQ 整合
第一步，把EntLib的Unity作为ASP.NET MVC Controller管理容器。

创建自定义的Controller工厂，通过Unity实力话Controller。

/// <summary>
/// EntLib IoC容器和ASP.NET MVC Controller集成工厂。
/// </summary>
public class UnityControllerFactory : DefaultControllerFactory
{
    private IUnityContainer unityContaier;

    /// <summary>
    ///
    /// </summary>
    /// <param name="unityContaier">EntLib IOC容器</param>
    public UnityControllerFactory(IUnityContainer unityContaier)
    {
        this.unityContaier = unityContaier;
    }


    #region IControllerFactory Members

    protected override IController CreateController(RequestContext context, string controllerName)
    {
        Type type = base.GetControllerType(controllerName);
        return unityContaier.Resolve(type) as IController;
    }

    #endregion
}

    /// <summary>
/// EntLib IoC容器和ASP.NET MVC Controller集成工厂。
/// </summary>
public class UnityControllerFactory : DefaultControllerFactory
{
private IUnityContainer unityContaier;
/// <summary>
///
/// </summary>
/// <param name="unityContaier">EntLib IOC容器</param>
public UnityControllerFactory(IUnityContainer unityContaier)
{
this.unityContaier = unityContaier;
}
#region IControllerFactory Members
protected override IController CreateController(RequestContext context, string controllerName)
{
Type type = base.GetControllerType(controllerName);
return unityContaier.Resolve(type) as IController;
}
#endregion
}

在Global.asax.cs加上初始化UnityContaner的代码。

protected void Application_Start()
{
    RegisterRoutes(RouteTable.Routes);

    this.InitializeContainer();
}

protected virtual void InitializeContainer()
{
    IUnityContainer container = new UnityContainer();

    UnityConfigurationSection section = (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
    section.Containers["dataContainer"].Configure(container);

    Type controllerType = typeof(IController);
    foreach (Type type in Assembly.GetExecutingAssembly().GetTypes())
    {
        if (controllerType.IsAssignableFrom(type))
        {
            container.RegisterType(type, type);
        }
    }

    UnityControllerFactory factory = new UnityControllerFactory(container);
    ControllerBuilder.Current.SetControllerFactory(factory);
}

        protected void Application_Start()
{
RegisterRoutes(RouteTable.Routes);
this.InitializeContainer();
}
protected virtual void InitializeContainer()
{
IUnityContainer container = new UnityContainer();
UnityConfigurationSection section = (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
section.Containers["dataContainer"].Configure(container);
Type controllerType = typeof(IController);
foreach (Type type in Assembly.GetExecutingAssembly().GetTypes())
{
if (controllerType.IsAssignableFrom(type))
{
container.RegisterType(type, type);
}
}
UnityControllerFactory factory = new UnityControllerFactory(container);
ControllerBuilder.Current.SetControllerFactory(factory);
}

web.config配置

<unity>
  <typeAliases>
    <typeAlias alias="transient"
         type="Microsoft.Practices.Unity.TransientLifetimeManager,
           Microsoft.Practices.Unity" />
  </typeAliases>
  <containers>
    <container name="dataContainer">
      <types>
        <type type="Shengjing360.EDM.Task.Daos.ITaskPlanDao,Shengjing360.EDM.Task" mapTo="Shengjing360.EDM.Task.DaoImpl.TaskPlanDaoImpl,Shengjing360.EDM.Task.DaoImpl">
          <lifetime type="transient" />
        </type>
      </types>
      <extensions>
        <add type="Microsoft.Practices.EnterpriseLibrary.Common.Configuration.Unity.EnterpriseLibraryCoreExtension, Microsoft.Practices.EnterpriseLibrary.Common" />
        <add type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.Unity.DataAccessBlockExtension, Microsoft.Practices.EnterpriseLibrary.Data" />
      </extensions>
    </container>
  </containers>
</unity>

  <unity>
<typeAliases>
<typeAlias alias="transient"
type="Microsoft.Practices.Unity.TransientLifetimeManager,
Microsoft.Practices.Unity" />
</typeAliases>
<containers>
<container name="dataContainer">
<types>
<type type="Shengjing360.EDM.Task.Daos.ITaskPlanDao,Shengjing360.EDM.Task" mapTo="Shengjing360.EDM.Task.DaoImpl.TaskPlanDaoImpl,Shengjing360.EDM.Task.DaoImpl">
<lifetime type="transient" />
</type>
</types>
<extensions>
<add type="Microsoft.Practices.EnterpriseLibrary.Common.Configuration.Unity.EnterpriseLibraryCoreExtension, Microsoft.Practices.EnterpriseLibrary.Common" />
<add type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.Unity.DataAccessBlockExtension, Microsoft.Practices.EnterpriseLibrary.Data" />
</extensions>
</container>
</containers>
</unity>

以上就是整合Unity的代码，EntLib的详细不配置就不贴了。

下面，扩展Unity，Unity的生命周期管理只有，transient，external，singleton，我要增加一个request的，一个request请求一个实例，然后在request介绍的时候，回收资源。

首先，定义自己的DataContext

public class ShengjingDataContext : DataContext
{
    /// <summary>
    ///
    /// </summary>
    /// <param name="db"></param>
    [InjectionConstructor]
    public ShengjingDataContext([Dependency]Database db ) : base(db.CreateConnection())
    {
        this.Database = db;

        this.Log = Console.Out;
    }

    /// <summary>
    /// 数据库
    /// </summary>
    public Database Database { get; private set; }
}

    public class ShengjingDataContext : DataContext
{
/// <summary>
///
/// </summary>
/// <param name="db"></param>
[InjectionConstructor]
public ShengjingDataContext([Dependency]Database db ) : base(db.CreateConnection())
{
this.Database = db;
this.Log = Console.Out;
}
/// <summary>
/// 数据库
/// </summary>
public Database Database { get; private set; }
}

第二，增加一个Resquest级别的LifetimeManager，HttpContext.Items中数据是Request期间共享数据用的，所以HttpContext.Items中放一个字典，用类型为key，类型的实例为value。如果当前Context.Items中有类型的实例，就直接返回实例。

public class RequestScopeLifetimeManager : LifetimeManager
{
    private Type objectType;

    /// <summary>
    ///
    /// </summary>
    /// <param name="t"></param>
    public RequestScopeLifetimeManager(Type t)
    {
        this.objectType = t;
    }

    private IDictionary<Type,object> GetObjectTable()
    {
        IDictionary<Type, object> objects = HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS]
            as IDictionary<Type, object>;
        if (objects == null)
        {
            lock (this)
            {
                if (HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS] == null)
                {
                    objects = new Dictionary<Type, object>();
                    HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS] = objects;
                }
                else
                {
                    return HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS]
                        as IDictionary<Type, object>;
                }
            }
        }
        return objects;
    }

    public override object GetValue()
    {
        IDictionary<Type, object> objects = this.GetObjectTable();
        object obj = null;
        if (objects.TryGetValue(this.objectType,out obj))
        {
            return obj;
        }
        return null;
    }

    public override void RemoveValue()
    {
        IDictionary<Type, object> objects = this.GetObjectTable();
        object obj = null;
        if (objects.TryGetValue(this.objectType, out obj))
        {
            ((IDisposable)obj).Dispose();
            objects.Remove(this.objectType);
        }
    }

    public override void SetValue(object newValue)
    {
        IDictionary<Type, object> objects = this.GetObjectTable();
        objects.Add(this.objectType, newValue);
    }
}

    public class RequestScopeLifetimeManager : LifetimeManager
{
private Type objectType;
/// <summary>
///
/// </summary>
/// <param name="t"></param>
public RequestScopeLifetimeManager(Type t)
{
this.objectType = t;
}
private IDictionary<Type,object> GetObjectTable()
{
IDictionary<Type, object> objects = HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS]
as IDictionary<Type, object>;
if (objects == null)
{
lock (this)
{
if (HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS] == null)
{
objects = new Dictionary<Type, object>();
HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS] = objects;
}
else
{
return HttpContext.Current.Items[UnityHttpMoudle.UNITY_OBJECTS]
as IDictionary<Type, object>;
}
}
}
return objects;
}
public override object GetValue()
{
IDictionary<Type, object> objects = this.GetObjectTable();
object obj = null;
if (objects.TryGetValue(this.objectType,out obj))
{
return obj;
}
return null;
}
public override void RemoveValue()
{
IDictionary<Type, object> objects = this.GetObjectTable();
object obj = null;
if (objects.TryGetValue(this.objectType, out obj))
{
((IDisposable)obj).Dispose();
objects.Remove(this.objectType);
}
}
public override void SetValue(object newValue)
{
IDictionary<Type, object> objects = this.GetObjectTable();
objects.Add(this.objectType, newValue);
}
}

写一个HttpMoudle,在Request结束的时候回收资源。

public class UnityHttpMoudle : IHttpModule
{
    internal const string UNITY_OBJECTS = "UNITY_OBJECTS";

    #region IHttpModule Members

    public void Dispose()
    {

    }

    public void Init(HttpApplication context)
    {
        context.EndRequest += new EventHandler(context_EndRequest);
    }

    private void context_EndRequest(object sender, EventArgs e)
    {
        IDictionary<Type, object> objects = HttpContext.Current.Items[UNITY_OBJECTS]
            as IDictionary<Type, object>;
        if (objects != null)
        {
            foreach (Type key in objects.Keys)
            {
                if (objects[key] is IDisposable)
                {
                    ((IDisposable)objects[key]).Dispose();
                }
            }
            HttpContext.Current.Items.Remove(UNITY_OBJECTS);
        }
    }

    #endregion
}

    public class UnityHttpMoudle : IHttpModule
{
internal const string UNITY_OBJECTS = "UNITY_OBJECTS";
#region IHttpModule Members
public void Dispose()
{
}
public void Init(HttpApplication context)
{
context.EndRequest += new EventHandler(context_EndRequest);
}
private void context_EndRequest(object sender, EventArgs e)
{
IDictionary<Type, object> objects = HttpContext.Current.Items[UNITY_OBJECTS]
as IDictionary<Type, object>;
if (objects != null)
{
foreach (Type key in objects.Keys)
{
if (objects[key] is IDisposable)
{
((IDisposable)objects[key]).Dispose();
}
}
HttpContext.Current.Items.Remove(UNITY_OBJECTS);
}
}
#endregion
}

最后，把他们变成Unity的扩展。

public class ShengjingExtension : UnityContainerExtension
{
    protected override void Initialize()
    {
        this.Container.RegisterType<RequestScopeLifetimeManager, RequestScopeLifetimeManager>();

        this.Container.RegisterType<ShengjingDataContext, ShengjingDataContext>(new RequestScopeLifetimeManager(typeof(ShengjingDataContext)));
    }
}

    public class ShengjingExtension : UnityContainerExtension
{
protected override void Initialize()
{
this.Container.RegisterType<RequestScopeLifetimeManager, RequestScopeLifetimeManager>();
this.Container.RegisterType<ShengjingDataContext, ShengjingDataContext>(new RequestScopeLifetimeManager(typeof(ShengjingDataContext)));
}
}

在webconfig的配置文件中增加

<unity>
……
<extensions>
……
<add type="Shengjing360.Utility.ShengjingExtension,Shengjing360.Utility" />
</extensions>
<unity>
……
<httpModules>
……
      <add name="UnityModule" type="Shengjing360.Utility.UnityHttpMoudle,Shengjing360.Utility"/>
    </httpModules>

<unity>
……
<extensions>
……
<add type="Shengjing360.Utility.ShengjingExtension,Shengjing360.Utility" />
</extensions>
<unity>
……
<httpModules>
……
<add name="UnityModule" type="Shengjing360.Utility.UnityHttpMoudle,Shengjing360.Utility"/>
</httpModules>

那么在数据访问对象实现就可以这样写

public class TaskPlanDaoImpl : ITaskPlanDao
{
    private ShengjingDataContext dbContext;

    /// <summary>
    ///
    /// </summary>
    /// <param name="dbContext"></param>
    [InjectionConstructor]
    public TaskPlanDaoImpl([Dependency]ShengjingDataContext dbContext)
    {
        this.dbContext = dbContext;
    }

    #region ITaskPlanDao Members

    /// <summary>
    ///
    /// </summary>
    /// <returns></returns>
    public TaskPlan[] FindAll()
    {
        var taskPlans = from taskPlan in dbContext.GetTable<TaskPlan>()
                        orderby taskPlan.PlanID descending
                        select taskPlan;

        return taskPlans.ToArray<TaskPlan>();
    }

    /// <summary>
    ///
    /// </summary>
    /// <param name="id"></param>
    /// <returns></returns>
    public TaskPlan FindByID(int id)
    {
        var taskPlans = from taskPlan in dbContext.GetTable<TaskPlan>()
                        where taskPlan.PlanID == id
                        select taskPlan;

        if (taskPlans.Count() > 0)
        {
            return taskPlans.First<TaskPlan>();
        }
        return null;
    }

    /// <summary>
    ///
    /// </summary>
    /// <param name="taskPlan"></param>
    /// <returns></returns>
    public int SaveOrUpdate(TaskPlan taskPlan)
    {
        Table<TaskPlan> table = this.dbContext.GetTable<TaskPlan>();
        if (taskPlan.PlanID == 0)
        {
            table.InsertOnSubmit(taskPlan);
        }

        this.dbContext.SubmitChanges();
        return taskPlan.PlanID;
    }

    /// <summary>
    ///
    /// </summary>
    /// <param name="id"></param>
    public void DeleteByID(int id)
    {
        Table<TaskPlan> table = this.dbContext.GetTable<TaskPlan>();
        table.DeleteOnSubmit(table.First<TaskPlan>(p => p.PlanID == id));
        this.dbContext.SubmitChanges();
    }

    #endregion
}

    public class TaskPlanDaoImpl : ITaskPlanDao
{
private ShengjingDataContext dbContext;
/// <summary>
///
/// </summary>
/// <param name="dbContext"></param>
[InjectionConstructor]
public TaskPlanDaoImpl([Dependency]ShengjingDataContext dbContext)
{
this.dbContext = dbContext;
}
#region ITaskPlanDao Members
/// <summary>
///
/// </summary>
/// <returns></returns>
public TaskPlan[] FindAll()
{
var taskPlans = from taskPlan in dbContext.GetTable<TaskPlan>()
orderby taskPlan.PlanID descending
select taskPlan;
return taskPlans.ToArray<TaskPlan>();
}
/// <summary>
///
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public TaskPlan FindByID(int id)
{
var taskPlans = from taskPlan in dbContext.GetTable<TaskPlan>()
where taskPlan.PlanID == id
select taskPlan;
if (taskPlans.Count() > 0)
{
return taskPlans.First<TaskPlan>();
}
return null;
}
/// <summary>
///
/// </summary>
/// <param name="taskPlan"></param>
/// <returns></returns>
public int SaveOrUpdate(TaskPlan taskPlan)
{
Table<TaskPlan> table = this.dbContext.GetTable<TaskPlan>();
if (taskPlan.PlanID == 0)
{
table.InsertOnSubmit(taskPlan);
}
this.dbContext.SubmitChanges();
return taskPlan.PlanID;
}
/// <summary>
///
/// </summary>
/// <param name="id"></param>
public void DeleteByID(int id)
{
Table<TaskPlan> table = this.dbContext.GetTable<TaskPlan>();
table.DeleteOnSubmit(table.First<TaskPlan>(p => p.PlanID == id));
this.dbContext.SubmitChanges();
}
#endregion
}

在Controller中也可以直接注入

        [Dependency]
        public ITaskPlanDao taskPlanDao { get; set; }

……

        /// <summary>
        ///
        /// </summary>
        /// <returns></returns>
        public ActionResult SaveOrUpdate()
        {
            int planID = String.IsNullOrEmpty(this.Request.Form["PlanID"]) ?
                0 :
                Int32.Parse(this.Request.Form["PlanID"]);

            TaskPlan taskPlan = planID == 0 ?
                new TaskPlan() { PlanID = planID } :
                this.taskPlanDao.FindByID(planID);

            taskPlan.Name = this.Request.Form["Name"].Trim();
            taskPlan.Description = this.Request.Form["Description"].Trim();
            taskPlan.MondayDef = this.Request.Form["MondayDef"].Trim();
            taskPlan.SaturdayDef = this.Request.Form["SaturdayDef"].Trim();
            taskPlan.SundayDef = this.Request.Form["SundayDef"].Trim();
            taskPlan.ThursdayDef = this.Request.Form["ThursdayDef"].Trim();
            taskPlan.TuesdayDef = this.Request.Form["TuesdayDef"].Trim();
            taskPlan.WednesdayDef = this.Request.Form["WednesdayDef"].Trim();
            taskPlan.FridayDef = this.Request.Form["FridayDef"].Trim();

            this.taskPlanDao.SaveOrUpdate(taskPlan);
            return this.RedirectToAction("Browse");
        }

        [Dependency]
public ITaskPlanDao taskPlanDao { get; set; }
……
/// <summary>
///
/// </summary>
/// <returns></returns>
public ActionResult SaveOrUpdate()
{
int planID = String.IsNullOrEmpty(this.Request.Form["PlanID"]) ?
0 :
Int32.Parse(this.Request.Form["PlanID"]);
TaskPlan taskPlan = planID == 0 ?
new TaskPlan() { PlanID = planID } :
this.taskPlanDao.FindByID(planID);
taskPlan.Name = this.Request.Form["Name"].Trim();
taskPlan.Description = this.Request.Form["Description"].Trim();
taskPlan.MondayDef = this.Request.Form["MondayDef"].Trim();
taskPlan.SaturdayDef = this.Request.Form["SaturdayDef"].Trim();
taskPlan.SundayDef = this.Request.Form["SundayDef"].Trim();
taskPlan.ThursdayDef = this.Request.Form["ThursdayDef"].Trim();
taskPlan.TuesdayDef = this.Request.Form["TuesdayDef"].Trim();
taskPlan.WednesdayDef = this.Request.Form["WednesdayDef"].Trim();
taskPlan.FridayDef = this.Request.Form["FridayDef"].Trim();
this.taskPlanDao.SaveOrUpdate(taskPlan);
return this.RedirectToAction("Browse");
}

DataContext本身是有缓存的，整个Request内都是一个DataContext，DataContext一级缓存能力进一步利用，当然，二级缓存才是王道。