C# 如何刷新 DbContext

How to Refresh DbContext

提问by Mohsen

I want to refresh all entities of my DbContextwithout recreating it, I tried the following and none of them make sense:

我想在DbContext不重新创建它的情况下刷新我的所有实体，我尝试了以下操作，但没有一个是有意义的：

var context = ((IObjectContextAdapter)myDbContext).ObjectContext;

var refreshableObjects = (from entry in context.ObjectStateManager.GetObjectStateEntries(
                                   EntityState.Added
                                   | EntityState.Deleted
                                   | EntityState.Modified
                                   | EntityState.Unchanged)
                          where entry.EntityKey != null
                          select entry.Entity);

context.Refresh(RefreshMode.StoreWins, refreshableObjects);
//.......................................................................
foreach (var entry in this.Orm.ChangeTracker.Entries())
{
    entry.State = EntityState.Unchanged;
}
this.Orm.ChangeTracker.DetectChanges();

And the only one which refreshes my DbContext:

唯一一个刷新我的DbContext：

foreach (var i in this.Orm.ChangeTracker.Entries())
    i.Reload();

But it's too slow. Can you help me choosing the right way?

但它太慢了。你能帮我选择正确的方式吗？

采纳答案by Mohsen

I just found that the Enumerableresult should be evaluated because the Refreshmethod gets it as object and doesn't evaluate it.

我刚刚发现Enumerable应该评估结果，因为该Refresh方法将它作为对象而不是评估它。

var context = ((IObjectContextAdapter)myDbContext).ObjectContext;
var refreshableObjects = (from entry in context.ObjectStateManager.GetObjectStateEntries(
                                           EntityState.Added
                                           | EntityState.Deleted
                                           | EntityState.Modified
                                           | EntityState.Unchanged)
                          where entry.EntityKey != null
                          select entry.Entity).ToList();

context.Refresh(RefreshMode.StoreWins, refreshableObjects);

And I prefer the following:

我更喜欢以下内容：

var refreshableObjects = myDbContext.ChangeTracker.Entries().Select(c=>c.Entity).ToList();
context.Refresh(RefreshMode.StoreWins, refreshableObjects);

回答by yonexbat

I checked this and id works fine:

我检查了这个，id 工作正常：

//Search
Box box = dbContext.Boxes.FirstOrDefault(x => x.BoxId == 45);

//breakpoint here, change Name of Box by sql management studio

//Refresh
var context = ((IObjectContextAdapter)dbContext).ObjectContext;
context.Refresh(System.Data.Entity.Core.Objects.RefreshMode.StoreWins, box);

//Check refresh and if it is in context
box = dbContext.Boxes.FirstOrDefault(x => x.BoxId == 45);

Are you sure it is the same db-context?

你确定它是相同的数据库上下文吗？

回答by Sean M

using System.Data.Entity.Core.Objects;
using System.Data.Entity.Infrastructure;
using System.Linq;

namespace System.Data.Entity
{
    public static class DbContextExtensions
    {
        /// <summary>
        /// Refresh non-detached entities
        /// </summary>
        /// <param name="dbContext">context of the entities</param>
        /// <param name="refreshMode">store or client wins</param>
        /// <param name="entityType">when specified only entities of that type are refreshed. when null all non-detached entities are modified</param>
        /// <returns></returns>
        public static DbContext RefreshEntites(this DbContext dbContext, RefreshMode refreshMode, Type entityType)
        {
            //https://christianarg.wordpress.com/2013/06/13/entityframework-refreshall-loaded-entities-from-database/
            var objectContext = ((IObjectContextAdapter)dbContext).ObjectContext;
            var refreshableObjects = objectContext.ObjectStateManager
                .GetObjectStateEntries(EntityState.Added | EntityState.Deleted | EntityState.Modified | EntityState.Unchanged)
                .Where(x => entityType == null || x.Entity.GetType() == entityType)
                .Where(entry => entry.EntityKey != null)
                .Select(e => e.Entity)
                .ToArray();

            objectContext.Refresh(RefreshMode.StoreWins, refreshableObjects);

            return dbContext;
        }

        public static DbContext RefreshAllEntites(this DbContext dbContext, RefreshMode refreshMode)
        {
            return RefreshEntites(dbContext: dbContext, refreshMode: refreshMode, entityType: null); //null entityType is a wild card
        }

        public static DbContext RefreshEntites<TEntity>(this DbContext dbContext, RefreshMode refreshMode)
        {
            return RefreshEntites(dbContext: dbContext, refreshMode: refreshMode, entityType: typeof(TEntity));
        }
    }
}

回答by Anthony Brenelière

In some cases, if a collection has been updated by a third party app, the collection may not be reloaded when refreshing the collection's object.

在某些情况下，如果某个集合已被第三方应用程序更新，则在刷新该集合的对象时可能不会重新加载该集合。

I had the case where I had an object A with a one to many relashionship to an object B.

我遇到过这样的情况，我有一个对象 A 与对象 B 有一对多的关系。

Application 1 loads an object A with A.ListB empty. Application 2 fills the A.ListB collection. Application 1 reloads the object A.

应用程序 1 加载一个对象 A，其中 A.ListB 为空。应用程序 2 填充 A.ListB 集合。应用程序 1 重新加载对象 A。

With the solution above, A.ListB remains empty. I had to reload the collection A.ListB explicitly.

使用上述解决方案，A.ListB 保持为空。我不得不显式地重新加载集合 A.ListB。

Here is a generic way to have all collections reloaded:

这是重新加载所有集合的通用方法：

var context = ((IObjectContextAdapter)this).ObjectContext;

// detach all added entities
ChangeTracker.Entries().Where(e => e.State == EntityState.Added).ToList().ForEach(e => e.State = EntityState.Detached);

// select entities
var refreshableObjects = ChangeTracker.Entries().Select(e => e.Entity).ToList();

// refresh each refreshable object
foreach (var @object in refreshableObjects)
{
    // refresh each collection of the object
    context.ObjectStateManager.GetRelationshipManager(@object).GetAllRelatedEnds().Where( r => r.IsLoaded).ToList().ForEach( c => c.Load() );

    // refresh the object
    context.Refresh(RefreshMode.StoreWins, @object);
}

回答by Cristinadeveloper

I had a trigger after insert in the database and I was working inside a transaction, so I needed to get the new values generated by the trigger in the same context. This worked for me:

我在数据库中插入后有一个触发器并且我在事务中工作，所以我需要在相同的上下文中获取触发器生成的新值。这对我有用：

using (var ctx = new context())
{
    ctx.Connection.Open();
    ctx.Transaction = ctx.Connection.BeginTransaction();

    ctx.Entities.InsertOnSubmit(itemDB);
    ctx.SubmitChanges();
    ctx.Refresh(RefreshMode.OverwriteCurrentValues, itemDB);

    Model newModel = itemDB.ToModel();

    ctx.Transaction.Commit();
    return newModel;
}
catch (Exception ex)
{
    ctx.Transaction.Rollback();
}