Entity Framework之深入分析

            BlogCategory cate = null;
            using (DemoDBEntities context = new DemoDBEntities())
            {
                //context.Configuration.LazyLoadingEnabled = false;
                DbSet<BlogCategory> set = context.Set<BlogCategory>();
                cate = set.Find(2);   
            }

            //肯定会出错 因为DbContext被释放了 无法延迟加载对象
            BlogArticle blog = cate.BlogArticle.First();

 static void Main(string[] args)
        {
            BlogCategory cate = null;
            using (DemoDBEntities context = new DemoDBEntities())
            {
                //context.Configuration.LazyLoadingEnabled = false;
                DbSet<BlogCategory> set = context.Set<BlogCategory>();
                cate = set.Find(2);

                //肯定会出错 因为DbContext被释放了 无法延迟加载对象
                BlogArticle blog = cate.BlogArticle.First();
            }
           
            Console.ReadLine();           
        }

public virtual int SaveChanges(SaveOptions options)
{
    this.OnSavingChanges();
    if ((SaveOptions.DetectChangesBeforeSave & options) != SaveOptions.None)
    {
        this.ObjectStateManager.DetectChanges();
    }
    if (this.ObjectStateManager.SomeEntryWithConceptualNullExists())
    {
        throw new InvalidOperationException(Strings.ObjectContext_CommitWithConceptualNull);
    }
    bool flag = false;
    int objectStateEntriesCount = this.ObjectStateManager.GetObjectStateEntriesCount(EntityState.Modified | EntityState.Deleted | EntityState.Added);
    using (new EntityBid.ScopeAuto("<dobj.ObjectContext.SaveChanges|API> %d#, affectingEntries=%d", this.ObjectID, objectStateEntriesCount))
    {
        EntityConnection connection = (EntityConnection) this.Connection;
        if (0 >= objectStateEntriesCount)
        {
            return objectStateEntriesCount;
        }
        if (this._adapter == null)
        {
            IServiceProvider providerFactory = connection.ProviderFactory as IServiceProvider;
            if (providerFactory != null)
            {
                this._adapter = providerFactory.GetService(typeof(IEntityAdapter)) as IEntityAdapter;
            }
            if (this._adapter == null)
            {
                throw EntityUtil.InvalidDataAdapter();
            }
        }
        this._adapter.AcceptChangesDuringUpdate = false;
        this._adapter.Connection = connection;
        this._adapter.CommandTimeout = this.CommandTimeout;
        try
        {
            this.EnsureConnection();
            flag = true;
            Transaction current = Transaction.Current;
            bool flag2 = false;
            if (connection.CurrentTransaction == null)
            {
                flag2 = null == this._lastTransaction;
            }
            using (DbTransaction transaction = null)
            {
                if (flag2)
                {
                    transaction = connection.BeginTransaction();
                }
                objectStateEntriesCount = this._adapter.Update(this.ObjectStateManager);
                if (transaction != null)
                {
                    transaction.Commit();
                }
            }
        }
        finally
        {
            if (flag)
            {
                this.ReleaseConnection();
            }
        }
        if ((SaveOptions.AcceptAllChangesAfterSave & options) == SaveOptions.None)
        {
            return objectStateEntriesCount;
        }
        try
        {
            this.AcceptAllChanges();
        }
        catch (Exception exception)
        {
            if (EntityUtil.IsCatchableExceptionType(exception))
            {
                throw EntityUtil.AcceptAllChangesFailure(exception);
            }
            throw;
        }
    }
    return objectStateEntriesCount;
}

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using EF.Model;
using EF.DAL;
using System.Data.Entity;
using System.Collections;
using System.Transactions;
namespace EF.Demo
{
    class Program
    {
        static void Main(string[] args)
        {
            BlogCategory cate = null;
            DemoDBEntities context = new DemoDBEntities();

            //DemoDBEntities context2 = new DemoDBEntities();
            try
            {
                //using (TransactionScope scope = new TransactionScope())
                //{
                    //context.Configuration.LazyLoadingEnabled = false;
                    DbSet<BlogCategory> set = context.Set<BlogCategory>();

                    cate = new BlogCategory();
                    cate.CateName = "2010-7";
                    cate.CreateTime = DateTime.Now;

                    cate.BlogArticle.Add(new BlogArticle() { Title = "2011-7-15" });
                    set.Add(cate);

                    //由于没设置Title字段,并且CreateTime字段不能为空，故会引发异常
                    context.Set<BlogArticle>().Add(new BlogArticle { BlogCategory_CateID = 2 });
                    int a = context.SaveChanges();

                //    context2.Set<BlogArticle>().Add(new BlogArticle { BlogCategory_CateID = 2 });
                //    int b = context2.SaveChanges();

                //    scope.Complete();
                //}
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            

            Console.ReadLine();           
        }
    }    
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using EF.Model;
using EF.DAL;
using System.Data.Entity;
using System.Collections;
using System.Transactions;
namespace EF.Demo
{
    class Program
    {
        static void Main(string[] args)
        {
            BlogCategory cate = null;
            DemoDBEntities context = new DemoDBEntities();

            DemoDBEntities context2 = new DemoDBEntities();
            try
            {
                using (TransactionScope scope = new TransactionScope())
                {
                    //context.Configuration.LazyLoadingEnabled = false;
                    DbSet<BlogCategory> set = context.Set<BlogCategory>();

                    cate = new BlogCategory();
                    cate.CateName = "2010-7";
                    cate.CreateTime = DateTime.Now;

                    cate.BlogArticle.Add(new BlogArticle() { Title = "2011-7-15" });
                    set.Add(cate);
                    //实例1 对数据库执行提交
                    int a = context.SaveChanges();

                    //实例2 模拟其它数据库提交 时间字段为空，无法更新成功
                    context2.Set<BlogArticle>().Add(new BlogArticle { Title="2011-7-16", BlogCategory_CateID = 2 });
                    int b = context2.SaveChanges();

                    scope.Complete();
                }
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            

            Console.ReadLine();           
        }
    }    
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace EF.Model
{
    public interface IUnitOfWork
    {
        //事务提交
        int Save();   
    }
}

<#@ template language="C#" debug="false" hostspecific="true"#>
<#@ include file="EF.Utility.CS.ttinclude"#><#@
 output extension=".cs"#><#

var loader = new MetadataLoader(this);
var region = new CodeRegion(this);
//---------------------------------------------------这里导入了DemoDB.edmx映射文件---------------add by mecity
var inputFile = @"DemoDB.edmx";
//---------------------------------------------------映射文件转为集合方便模板篇历生成代码--------add by mecity
var ItemCollection = loader.CreateEdmItemCollection(inputFile);

Code = new CodeGenerationTools(this);
EFTools = new MetadataTools(this);
ObjectNamespace = Code.VsNamespaceSuggestion();
ModelNamespace = loader.GetModelNamespace(inputFile);

EntityContainer container = ItemCollection.GetItems<EntityContainer>().FirstOrDefault();
if (container == null)
{
    return string.Empty;
}
#>
//------------------------------------------------------------------------------
// <auto-generated>
// <#=GetResourceString("Template_GeneratedCodeCommentLine1")#>
//
// <#=GetResourceString("Template_GeneratedCodeCommentLine2")#>
// <#=GetResourceString("Template_GeneratedCodeCommentLine3")#>
// </auto-generated>
//------------------------------------------------------------------------------

<#

if (!String.IsNullOrEmpty(ObjectNamespace))
{
#>
namespace <#=Code.EscapeNamespace(ObjectNamespace)#>
{
<#
    PushIndent(CodeRegion.GetIndent(1));
}

#>
using System;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
//---------------------------------------------------这加加入对EF.Model命名空间的引用---------------add by mecity
using EF.Model;
<#
if (container.FunctionImports.Any())
{
#>
using System.Data.Objects;
<#
}
#>

//---------------------------------------------------这里加入对IUnitOfWork接口继承---------------add by mecity
<#=Accessibility.ForType(container)#> partial class <#=Code.Escape(container)#> : DbContext,IUnitOfWork
{
    public <#=Code.Escape(container)#>()
        : base("name=<#=container.Name#>")
    {
<#
        WriteLazyLoadingEnabled(container);
#>
    }    

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        throw new UnintentionalCodeFirstException();
    }
    
    //---------------------------------------------------这里加入对IUnitOfWork接口方法的实现---------------add by mecity
    public int Save()
    {
        return base.SaveChanges();
    }

//------------------------------------------------------------------------------
// <auto-generated>
//    此代码是根据模板生成的。
//
//    手动更改此文件可能会导致应用程序中发生异常行为。
//    如果重新生成代码，则将覆盖对此文件的手动更改。
// </auto-generated>
//------------------------------------------------------------------------------

namespace EF.DAL
{
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Infrastructure;
    //---------------------------------------------------这加加入对EF.Model命名空间的引用---------------add by mecity
    using EF.Model;
    
    //---------------------------------------------------这里加入对IUnitOfWork接口继承---------------add by mecity
    public partial class DemoDBEntities : DbContext,IUnitOfWork
    {
        public DemoDBEntities()
            : base("name=DemoDBEntities")
        {
        }    
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }
        
        //---------------------------------------------------这里加入对IUnitOfWork接口方法的实现---------------add by mecity
        public int Save()
        {
            return base.SaveChanges();
        }
    
        public DbSet<BlogArticle> BlogArticle { get; set; }
        public DbSet<BlogCategory> BlogCategory { get; set; }
        public DbSet<BlogComment> BlogComment { get; set; }
        public DbSet<BlogDigg> BlogDigg { get; set; }
        public DbSet<BlogTag> BlogTag { get; set; }
        public DbSet<BlogMaster> BlogMaster { get; set; }
    }
}