上記のリンクの元のコードの作成者に非常に大きなうなずきを付けて、これが私が最終的に得たものです。基本的なシナリオはパスしますが、より深いナビゲーションおよび関連するクエリはまだ試していません。問題があっても、表示停止ではなくバグ修正になると思います。
ここに行きます。以下は再利用可能で、複数のコンテキストで動作し、データベースにアクセスして、クライアントの実際のコードの 2 行で何かを取得できることを意味します。
DataModel (クラス ライブラリ プロジェクト)
DbContext POCO などを含む EF Code First プロジェクト。
DbContextManagement (クラス ライブラリ プロジェクト)
DbContextManager.cs
namespace DbContextManagement
{
using System.Data.Entity;
/// <summary>
/// Abstract base class for all other DbContextManager classes.
/// </summary>
public abstract class DbContextManager
{
/// <summary>
/// Returns a reference to an DbContext instance.
/// </summary>
/// <typeparam name="TDbContext">The type of the db context.</typeparam>
/// <returns>The current DbContext</returns>
public abstract TDbContext GetDbContext<TDbContext>()
where TDbContext : DbContext, new();
}
}
DbContextScope.cs
namespace DbContextManagement
{
using System;
using System.Collections.Generic;
using System.Data.Common;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Linq;
using System.Threading;
/// <summary>
/// Defines a scope wherein only one DbContext instance is created, and shared by all of those who use it.
/// </summary>
/// <remarks>Instances of this class are supposed to be used in a using() statement.</remarks>
public class DbContextScope : IDisposable
{
/// <summary>
/// List of current DbContexts (supports multiple contexts).
/// </summary>
private readonly List<DbContext> contextList;
/// <summary>
/// DbContext scope definitiion.
/// </summary>
[ThreadStatic]
private static DbContextScope currentScope;
/// <summary>
/// Holds a value indicating whether the context is disposed or not.
/// </summary>
private bool isDisposed;
/// <summary>
/// Initializes a new instance of the <see cref="DbContextScope"/> class.
/// </summary>
/// <param name="saveAllChangesAtEndOfScope">if set to <c>true</c> [save all changes at end of scope].</param>
protected DbContextScope(bool saveAllChangesAtEndOfScope)
{
if (currentScope != null && !currentScope.isDisposed)
{
throw new InvalidOperationException("DbContextScope instances cannot be nested.");
}
this.SaveAllChangesAtEndOfScope = saveAllChangesAtEndOfScope;
this.contextList = new List<DbContext>();
this.isDisposed = false;
Thread.BeginThreadAffinity();
currentScope = this;
}
/// <summary>
/// Gets or sets a value indicating whether to automatically save all object changes at end of the scope.
/// </summary>
/// <value><c>true</c> if [save all changes at end of scope]; otherwise, <c>false</c>.</value>
private bool SaveAllChangesAtEndOfScope { get; set; }
/// <summary>
/// Save all object changes to the underlying datastore.
/// </summary>
public void SaveAllChanges()
{
var transactions = new List<DbTransaction>();
foreach (var context in this.contextList
.Select(dbcontext => ((IObjectContextAdapter)dbcontext)
.ObjectContext))
{
context.Connection.Open();
var databaseTransaction = context.Connection.BeginTransaction();
transactions.Add(databaseTransaction);
try
{
context.SaveChanges();
}
catch
{
/* Rollback & dispose all transactions: */
foreach (var transaction in transactions)
{
try
{
transaction.Rollback();
}
catch
{
// "Empty general catch clause suppresses any errors."
// Haven't quite figured out what to do here yet.
}
finally
{
databaseTransaction.Dispose();
}
}
transactions.Clear();
throw;
}
}
try
{
/* Commit all complete transactions: */
foreach (var completeTransaction in transactions)
{
completeTransaction.Commit();
}
}
finally
{
/* Dispose all transactions: */
foreach (var transaction in transactions)
{
transaction.Dispose();
}
transactions.Clear();
/* Close all open connections: */
foreach (var context in this.contextList
.Select(dbcontext => ((IObjectContextAdapter)dbcontext).ObjectContext)
.Where(context => context.Connection.State != System.Data.ConnectionState.Closed))
{
context.Connection.Close();
}
}
}
/// <summary>
/// Disposes the DbContext.
/// </summary>
public void Dispose()
{
// Monitor for possible future bugfix.
// CA1063 : Microsoft.Design : Provide an overridable implementation of Dispose(bool)
// on 'DbContextScope' or mark the type as sealed. A call to Dispose(false) should
// only clean up native resources. A call to Dispose(true) should clean up both managed
// and native resources.
if (this.isDisposed)
{
return;
}
// Monitor for possible future bugfix.
// CA1063 : Microsoft.Design : Modify 'DbContextScope.Dispose()' so that it calls
// Dispose(true), then calls GC.SuppressFinalize on the current object instance
// ('this' or 'Me' in Visual Basic), and then returns.
currentScope = null;
Thread.EndThreadAffinity();
try
{
if (this.SaveAllChangesAtEndOfScope && this.contextList.Count > 0)
{
this.SaveAllChanges();
}
}
finally
{
foreach (var context in this.contextList)
{
try
{
context.Dispose();
}
catch (ObjectDisposedException)
{
// Monitor for possible future bugfix.
// CA2202 : Microsoft.Usage : Object 'databaseTransaction' can be disposed
// more than once in method 'DbContextScope.SaveAllChanges()'.
// To avoid generating a System.ObjectDisposedException you should not call
// Dispose more than one time on an object.
}
}
this.isDisposed = true;
}
}
/// <summary>
/// Returns a reference to a DbContext of a specific type that is - or will be -
/// created for the current scope. If no scope currently exists, null is returned.
/// </summary>
/// <typeparam name="TDbContext">The type of the db context.</typeparam>
/// <returns>The current DbContext</returns>
protected internal static TDbContext GetCurrentDbContext<TDbContext>()
where TDbContext : DbContext, new()
{
if (currentScope == null)
{
return null;
}
var contextOfType = currentScope.contextList
.OfType<TDbContext>()
.FirstOrDefault();
if (contextOfType == null)
{
contextOfType = new TDbContext();
currentScope.contextList.Add(contextOfType);
}
return contextOfType;
}
}
}
FacadeBase.cs
namespace DbContextManagement
{
using System;
using System.Collections;
using System.Collections.Generic;
using System.Configuration;
using System.Data.Entity;
using System.Reflection;
/// <summary>
/// Generic base class for all other Facade classes.
/// </summary>
/// <typeparam name="TDbContext">The type of the db context.</typeparam>
/// <typeparam name="TEntity">The type of the entity.</typeparam>
/// <typeparam name="TEntityKey">The type of the entity key.</typeparam>
/// <remarks>Not sure the handling of TEntityKey is something I've worked with properly.</remarks>
public abstract class FacadeBase<TDbContext, TEntity, TEntityKey>
where TDbContext : DbContext, new()
where TEntity : class
{
/// <summary>
/// Gets the db context.
/// </summary>
public TDbContext DbContext
{
get
{
if (DbContextManager == null)
{
this.InstantiateDbContextManager();
}
return DbContextManager != null
? DbContextManager.GetDbContext<TDbContext>()
: null;
}
}
/// <summary>
/// Gets or sets the DbContextManager.
/// </summary>
/// <value>The DbContextManager.</value>
private DbContextManager DbContextManager { get; set; }
/// <summary>
/// Adds a new entity object to the context.
/// </summary>
/// <param name="newObject">A new object.</param>
public virtual void Add(TEntity newObject)
{
this.DbContext.Set<TEntity>().Add(newObject);
}
/// <summary>
/// Deletes an entity object.
/// </summary>
/// <param name="obsoleteObject">An obsolete object.</param>
public virtual void Delete(TEntity obsoleteObject)
{
this.DbContext.Set<TEntity>().Remove(obsoleteObject);
}
/// <summary>
/// Gets all entities for the given type.
/// </summary>
/// <returns>DbContext Set of TEntity.</returns>
public virtual IEnumerable<TEntity> GetAll()
{
return this.DbContext.Set<TEntity>();
}
/// <summary>
/// Gets the entity by the specified entity key.
/// </summary>
/// <param name="entityKey">The entity key.</param>
/// <returns>Entity matching specified entity key or null if not found.</returns>
public virtual TEntity GetByKey(TEntityKey entityKey)
{
return this.DbContext.Set<TEntity>().Find(entityKey);
}
/// <summary>
/// Deletes the entity for the specified entity key.
/// </summary>
/// <param name="entityKey">The entity key.</param>
public virtual void DeleteByKey(TEntityKey entityKey)
{
var entity = this.DbContext.Set<TEntity>().Find(entityKey);
if (entity != null)
{
this.DbContext.Set<TEntity>().Remove(entity);
}
}
/// <summary>
/// Instantiates a new DbContextManager based on application configuration settings.
/// </summary>
private void InstantiateDbContextManager()
{
/* Retrieve DbContextManager configuration settings: */
var contextManagerConfiguration = ConfigurationManager.GetSection("DbContext") as Hashtable;
if (contextManagerConfiguration == null)
{
throw new ConfigurationErrorsException("A Facade.DbContext tag or its managerType attribute is missing in the configuration.");
}
if (!contextManagerConfiguration.ContainsKey("managerType"))
{
throw new ConfigurationErrorsException("dbManagerConfiguration does not contain key 'managerType'.");
}
var managerTypeName = contextManagerConfiguration["managerType"] as string;
if (string.IsNullOrEmpty(managerTypeName))
{
throw new ConfigurationErrorsException("The managerType attribute is empty.");
}
managerTypeName = managerTypeName.Trim().ToUpperInvariant();
try
{
/* Try to create a type based on it's name: */
var frameworkAssembly = Assembly.GetAssembly(typeof(DbContextManager));
var managerType = frameworkAssembly.GetType(managerTypeName, true, true);
/* Try to create a new instance of the specified DbContextManager type: */
this.DbContextManager = Activator.CreateInstance(managerType) as DbContextManager;
}
catch (Exception e)
{
throw new ConfigurationErrorsException("The managerType specified in the configuration is not valid.", e);
}
}
}
}
ScopedDbContextManager.cs
namespace DbContextManagement
{
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
/// <summary>
/// Manages multiple db contexts.
/// </summary>
public sealed class ScopedDbContextManager : DbContextManager
{
/// <summary>
/// List of Object Contexts.
/// </summary>
private List<DbContext> contextList;
/// <summary>
/// Returns the DbContext instance that belongs to the current DbContextScope.
/// If currently no DbContextScope exists, a local instance of an DbContext
/// class is returned.
/// </summary>
/// <typeparam name="TDbContext">The type of the db context.</typeparam>
/// <returns>Current scoped DbContext.</returns>
public override TDbContext GetDbContext<TDbContext>()
{
var currentDbContext = DbContextScope.GetCurrentDbContext<TDbContext>();
if (currentDbContext != null)
{
return currentDbContext;
}
if (this.contextList == null)
{
this.contextList = new List<DbContext>();
}
currentDbContext = this.contextList.OfType<TDbContext>().FirstOrDefault();
if (currentDbContext == null)
{
currentDbContext = new TDbContext();
this.contextList.Add(currentDbContext);
}
return currentDbContext;
}
}
}
UnitOfWorkScope.cs
namespace DbContextManagement
{
/// <summary>
/// Defines a scope for a business transaction. At the end of the scope all object changes can be persisted to the underlying datastore.
/// </summary>
/// <remarks>Instances of this class are supposed to be used in a using() statement.</remarks>
public sealed class UnitOfWorkScope : DbContextScope
{
/// <summary>
/// Initializes a new instance of the <see cref="UnitOfWorkScope"/> class.
/// </summary>
/// <param name="saveAllChangesAtEndOfScope">if set to <c>true</c> [save all changes at end of scope].</param>
public UnitOfWorkScope(bool saveAllChangesAtEndOfScope)
: base(saveAllChangesAtEndOfScope)
{
}
}
}
Facade (クラス ライブラリ プロジェクト)
YourEntityFacade.cs
namespace Facade
{
using System.Collections.Generic;
using System.Linq;
using DataModel;
using DataModel.Entities;
using DbContextManagement;
public class YourEntityFacade : FacadeBase<YourDbContext, YourEntity, int>
{
public override IEnumerable<YourEntity> GetAll()
{
return base.GetAll()
.Distinct()
.ToList();
}
}
}
TestConsole (コンソール アプリケーション プロジェクト)
App.config
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<section name="DbContext" type="System.Configuration.SingleTagSectionHandler" />
</configSections>
<DbContext managerType="DbContextManagement.ScopedDbContextManager" />
<connectionStrings>
<add
name="YourDbContext"
providerName="System.Data.SqlClient"
connectionString="Your connection string" />
</connectionStrings>
</configuration>
Program.cs
namespace TestConsole
{
using System;
using System.Collections.Generic;
using DataModel.Entities;
using DbContextManagement;
using Facade;
public static class Program
{
public static void Main()
{
TestGetAll();
Console.ReadLine();
}
private static void TestGetAll()
{
Console.WriteLine();
Console.WriteLine("Test GetAll()");
Console.WriteLine();
IEnumerable<YourEntity> yourEntities;
using (new UnitOfWorkScope(false))
{
yourEntities= new YourEntityFacade().GetAll();
}
if (yourEntities != null)
{
foreach (var yourEntity in yourEntities)
{
Console.WriteLine(
string.Format("{0}, {1}",
yourEntity.Id,
yourEntity.Name));
}
}
else
{
Console.WriteLine("GetAll() NULL");
}
}
}
}
したがって、使い方は非常に簡単で、スコープ内で複数のコンテキストとファサードを操作できます。このアプローチでは、作成するコードはカスタム クエリだけです。リポジトリ参照で UnitOfWorks を際限なく更新したり、コピーキャット リポジトリを作成したりする必要はもうありません。素晴らしいと思いますが、これはベータ版のコードであり、プラグインが必要な大きな穴がどこかにあることに注意してください:)
すべての皆様、特に Ladislav の忍耐と、これおよび私が尋ねる他の多くの関連する質問に対する助けに感謝します。このコードが興味深いものであることを願っています。上記のブログで著者に連絡しましたが、まだ返信がありません。最近、彼は NHibernate に夢中になっていると思います。
リチャード