blocks|key|362407|text|这里有另一个选择。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|362408|在某些情况下，我更喜欢它，因为它不需要您专门运行查询来获得要克隆的数据。您可以使用此方法创建已从数据库中获得的实体的克隆。|362409|//Get+entity+to+be+cloned
var+source+=+Context.ExampleRows.FirstOrDefault();

//Create+and+add+clone+object+to+context+before+setting+its+values
var+clone+=+new+ExampleRow();
Context.ExampleRows.Add(clone);

//Copy+values+from+source+to+clone
var+sourceValues+=+Context.Entry(source).CurrentValues;
Context.Entry(clone).CurrentValues.SetValues(sourceValues);

//Change+values+of+the+copied+entity
clone.ExampleProperty+=+"New+Value";

//Insert+clone+with+changes+into+database
Context.SaveChanges();|code-block|syntax|javascript|362410|此方法将当前值从源复制到已添加的新行。|362411|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Here's another option. 

I prefer it in some cases because it does not require you to run a query specifically to get data to be cloned. You can use this method to create clones of entities you've already obtained from the database.

<pre class="lang-c# prettyprint-override"><code>//Get entity to be cloned
var source = Context.ExampleRows.FirstOrDefault();

//Create and add clone object to context before setting its values
var clone = new ExampleRow();
Context.ExampleRows.Add(clone);

//Copy values from source to clone
var sourceValues = Context.Entry(source).CurrentValues;
Context.Entry(clone).CurrentValues.SetValues(sourceValues);

//Change values of the copied entity
clone.ExampleProperty = "New Value";

//Insert clone with changes into database
Context.SaveChanges();
</code></pre>

This method copies the current values from the source to a new row that has been added.

blocks|key|144276|text|这是一个允许泛型克隆的泛型扩展方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|144277|您必须从nuget获取System.Linq.Dynamic。|offset|length|style|CODE|144278|++++public+TEntity+Clone<TEntity>(this+DbContext+context,+TEntity+entity)+where+TEntity+:+class
++++{

++++++++var+keyName+=+GetKeyName<TEntity>();
++++++++var+keyValue+=+context.Entry(entity).Property(keyName).CurrentValue;
++++++++var+keyType+=+typeof(TEntity).GetProperty(keyName,+System.Reflection.BindingFlags.Public+%7C+System.Reflection.BindingFlags.Instance).PropertyType;

++++++++var+dbSet+=+context.Set<TEntity>();
++++++++var+newEntity+=++dbSet
++++++++++++.Where(keyName+%2B+"+=+@0",+keyValue)
++++++++++++.AsNoTracking()
++++++++++++.Single();

++++++++context.Entry(newEntity).Property(keyName).CurrentValue+=+keyType.GetDefault();

++++++++context.Add(newEntity);

++++++++return+newEntity;
++++}|code-block|syntax|javascript|144279|您唯一需要自己实现的就是GetKeyName方法。这可以是从return+typeof(TEntity).Name+%2B+"Id"到return+the+first+guid+property的任何内容，也可以返回标记为DatabaseGenerated(DatabaseGeneratedOption.Identity)]的第一个属性。|144280|在我的例子中，我已经用[DataServiceKeyAttribute("EntityId")]标记了类|144281|++++private+string+GetKeyName<TEntity>()+where+TEntity+:+class
++++{
++++++++return+((DataServiceKeyAttribute)typeof(TEntity)
+++++++++++.GetCustomAttributes(typeof(DataServiceKeyAttribute),+true).First())
+++++++++++.KeyNames.Single();
++++}|144282|entityMap^0|0|B|J|0|0|U|Y|1T|U|31|1G|0|B|11|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@$D|W|E|X|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|Y|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|Z|8|@$D|10|E|11|F|G]|$D|12|E|13|F|G]|$D|14|E|15|F|G]]|9|@]|A|$]]|$1|O|3|P|5|6|7|16|8|@$D|17|E|18|F|G]]|9|@]|A|$]]|$1|Q|3|R|5|J|7|19|8|@]|9|@]|A|$K|L]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|T|$]]

This is a generic extension method which allows generic cloning.

You have to fetch <code>System.Linq.Dynamic</code> from nuget.

<pre><code> public TEntity Clone&lt;TEntity&gt;(this DbContext context, TEntity entity) where TEntity : class
 {

 var keyName = GetKeyName&lt;TEntity&gt;();
 var keyValue = context.Entry(entity).Property(keyName).CurrentValue;
 var keyType = typeof(TEntity).GetProperty(keyName, System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance).PropertyType;

 var dbSet = context.Set&lt;TEntity&gt;();
 var newEntity = dbSet
 .Where(keyName + " = @0", keyValue)
 .AsNoTracking()
 .Single();

 context.Entry(newEntity).Property(keyName).CurrentValue = keyType.GetDefault();

 context.Add(newEntity);

 return newEntity;
 }
</code></pre>

The only thing you have to implement yourself is the GetKeyName method. This could be anything from <code>return typeof(TEntity).Name + "Id"</code> to <code>return the first guid property</code> or return the first property marked with <code>DatabaseGenerated(DatabaseGeneratedOption.Identity)]</code>.

In my case I already marked my classes with <code>[DataServiceKeyAttribute("EntityId")]</code>

<pre><code> private string GetKeyName&lt;TEntity&gt;() where TEntity : class
 {
 return ((DataServiceKeyAttribute)typeof(TEntity)
 .GetCustomAttributes(typeof(DataServiceKeyAttribute), true).First())
 .KeyNames.Single();
 }
</code></pre>

blocks|key|362520|text|我在Entity+Framework+Core中遇到了同样的问题，当子实体被延迟加载时，深度克隆涉及多个步骤。克隆整个结构的一种方法如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|362521|+++var+clonedItem+=+Context.Parent.AsNoTracking()
++++++++.Include(u+=>+u.Child1)
++++++++.Include(u+=>+u.Child2)
++++++++//+deep+includes+might+go+here+(see+ThenInclude)
++++++++.FirstOrDefault(u+=>+u.ParentId+==+parentId);

++++//+remove+old+id+from+parent
++++clonedItem.ParentId+=+0;

++++//+remove+old+ids+from+children
++++clonedItem.Parent1.ForEach(x+=>
++++{
++++++++x.Child1Id+=+0;
++++++++x.ParentId=+0;
++++});
++++clonedItem.Parent2.ForEach(x+=>
++++{
++++++++x.Child2Id+=+0;
++++++++x.ParentId=+0;
++++});

++++//+customize+entities+before+inserting+it

++++//+mark+everything+for+insert
++++Context.Parent.Add(clonedItem);

++++//+save+everything+in+one+single+transaction
++++Context.SaveChanges();|code-block|syntax|javascript|362522|当然，有一些方法可以让泛型函数急于加载所有内容和/或重置所有键的值，但这应该使所有步骤变得非常清晰和可定制(例如，对于某些子项，通过跳过它们的包含，所有步骤都不被克隆)。|362523|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I had the same issue in Entity Framework Core where deep clone involves multiple steps when children entities are lazy loaded. One way to clone the whole structure is the following:

<pre><code> var clonedItem = Context.Parent.AsNoTracking()
 .Include(u =&gt; u.Child1)
 .Include(u =&gt; u.Child2)
 // deep includes might go here (see ThenInclude)
 .FirstOrDefault(u =&gt; u.ParentId == parentId);

 // remove old id from parent
 clonedItem.ParentId = 0;

 // remove old ids from children
 clonedItem.Parent1.ForEach(x =&gt;
 {
 x.Child1Id = 0;
 x.ParentId= 0;
 });
 clonedItem.Parent2.ForEach(x =&gt;
 {
 x.Child2Id = 0;
 x.ParentId= 0;
 });

 // customize entities before inserting it

 // mark everything for insert
 Context.Parent.Add(clonedItem);

 // save everything in one single transaction
 Context.SaveChanges();
</code></pre>

Of course, there are ways to make generic functions to eager load everything and/or reset values for all keys, but this should make all the steps much clear and customizable (e.g. all for some children to not be cloned at all, by skipping their Include).

I am using Entity Framework 5 (<code>DBContext</code>) and I am trying to find the best way to deep copy an entity (i.e. copy the entity and all related objects) and then save the new entities in the database. How can I do this? I have looked into using extension methods such as <code>CloneHelper</code> but I am not sure if it applies to <code>DBContext</code>.

Entity Framework 5 deep copy/clone of an entity

数据库

我正在使用Entity Framework5 (DBContext)，我正在尝试找到深度复制实体的最佳方法(即复制实体和所有相关对象)，然后将新实体保存在数据库中。我该怎么做呢？我曾研究过使用CloneHelper等扩展方法，但我不确定它是否适用于DBContext。

问Entity Framework 5实体的深度复制/克隆
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