c# - 如何刷新 DbContext

Question

我想刷新我的所有实体DbContext而不重新创建它，我尝试了以下方法，但它们都没有意义：

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();

唯一让我耳目一新的DbContext：

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

但是太慢了。你能帮我选择正确的方法吗？

score 39 · Accepted Answer

我刚刚发现Enumerable应该评估结果，因为该Refresh方法将其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);

我更喜欢以下内容：

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

score 14 · Accepted Answer

我检查了这个并且 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);

你确定它是同一个数据库上下文吗？

score 4 · Accepted Answer

在某些情况下，如果集合已被第三方应用程序更新，则在刷新集合的对象时可能不会重新加载集合。

我有一个案例，我有一个对象 A 与对象 B 有一对多的关系。

应用程序 1 加载 A.ListB 为空的对象 A。应用程序 2 填充 A.ListB 集合。应用程序 1 重新加载对象 A。

使用上述解决方案， A.ListB 仍然为空。我不得不重新加载集合 A.ListB 明确。

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);
}

score 3 · Accepted Answer

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));
        }
    }
}

score 1 · Accepted Answer

在数据库中插入后我有一个触发器，并且我在一个事务中工作，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();
}

c# - 如何刷新 DbContext

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