删除实体时如何忽略 DbUpdateConcurrencyException [英] How to ignore a DbUpdateConcurrencyException when deleting an entity

问题描述

我有一个应用程序可以将大量数据读入内存并分批处理.

I have an app that reads a lot of data into memory and processes it in a batches.

我想要的是实体框架在删除已删除的实体时忽略 DbUpdateConcurrencyException.

What I want is for entity framework to ignore DbUpdateConcurrencyException when deleting an entity that has already been deleted.

原因是当一个实体被处理并标记为删除时，它可能已经从数据库中删除了.

The reason is that by the time an entity has been processed and marked for deletion, it may already have been deleted from the DB.

显然删除已删除的行不是问题，也不应该导致错误，我只需要一种方法来告诉实体框架:)

Obliviously deleting a row that has already been deleted isn't a problem and shouldn't cause an error, I just need a way to tell entity framework that :)

示例

Db.Entry(itemToRemove).State = EntityState.Deleted;
Db.SaveChanges();

如果 itemToRemove 已被删除，则会导致错误.

Causes an error if itemToRemove has already been deleted.

注意:Db.Configuration.ValidateOnSaveEnabled = false; 没有像另一个线程建议的那样解决这个问题.

Note: Db.Configuration.ValidateOnSaveEnabled = false; doesn't fix this as another thread suggested.

推荐答案

怎么样?

Db.Entry(itemToRemove).State = EntityState.Deleted;

bool saveFailed;
do
{
    saveFailed = false;
    try
    {
       Db.SaveChanges();
    }
    catch(DbUpdateConcurrencyException ex)
    {
       saveFailed = true;
       var entry = ex.Entries.Single();
       //The MSDN examples use Single so I think there will be only one
       //but if you prefer - do it for all entries
       //foreach(var entry in ex.Entries)
       //{
       if(entry.State == EntityState.Deleted)
          //When EF deletes an item its state is set to Detached
          //http://msdn.microsoft.com/en-us/data/jj592676.aspx
          entry.State = EntityState.Detached;
       else
          entry.OriginalValues.SetValues(entry.GetDatabaseValues());
          //throw; //You may prefer not to resolve when updating
       //}
    }
} while (saveFailed);

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