基于Linq联接，我得到错误在先前操作完成之前，在此上下文中启动了第二个操作 [英] Based on a Linq join I get the error A second operation started on this context before a previous operation completed

问题描述

以下代码使用dbcontext.

The following code uses dbcontext.

var CurrentUser = await userManager.GetUserAsync(User);
var DefaultLanguageID = CurrentUser.DefaultLangauge;

var TestForNull = (from c in _classificationLevel.GetAllClassificationLevels()
  join l in _classificationLevelLanguage.GetAllClassificationLevelLanguages()
  on c.Id equals l.ClassificationLevelId
  where c.ClassificationId == NewLevel.SuObject.ObjectId
  && l.LanguageId == DefaultLanguageID
  select c.Sequence).Count();

运行它时，出现错误

A second operation started on this context before a previous operation completed.

我不确定为什么.我可以想象第一个操作是: userManager.GetUserAsync(User);

I am not sure why. I can imagine that the first operation is: userManager.GetUserAsync(User);

，并且在下一次启动时仍在运行.尽管它的关键字在前面.

and is still running while the next starts. Though it has the keyword await in front.

我认为的另一个选择是在查询中检索到两个表，并将其用于相同的dbcontext. 1. _classificationLevel.GetAllClassificationLevels() 2. _classificationLevelLanguage.GetAllClassificationLevelLanguages()

The other option I thought is that within the query two tables are retrieved and that it uses for both the same dbcontext. 1. _classificationLevel.GetAllClassificationLevels() 2. _classificationLevelLanguage.GetAllClassificationLevelLanguages()

这是错误的原因吗?

这些方法背后的方法是:

The methods behind these are:

public IEnumerable<SuClassificationLevelModel> GetAllClassificationLevels()
{
    return context.dbClassificationLevel.AsNoTracking();
}

和

public IEnumerable<SuClassificationLevelLanguageModel> GetAllClassificationLevelLanguages()
{
    return context.dbClassificationLevelLanguage;
}

我没有异步/等待这些.如果应该的话，我应该怎么做?

I don't have an async / await on these. Should I and if so, how should I do that?

在模型级别，两个模型是相关的，如下面的代码所示:

On a model level, the two models are related as shown in the code below:

public interface IClassificationAndStatusRepository
{
    IEnumerable<SuObjectVM> GetAllClassifications();
    IEnumerable<SuClassificationStatusModel> GetAllStatus();
}

推荐答案

调用的代码是同一模型的2倍:

The code called 2 times the same model:

var testForNull = await (from c in GetAllClassificationLevels()
                                 join l in GetAllClassificationLevelLanguages()
                                on c.Id equals l.ClassificationLevelId
                               where c.ClassificationId == NewLevel.SuObject.ObjectId
                               && l.LanguageId == defaultLanguageID
                                     select c.EmployeeID).CountAsync();

GetAllClassificationLevelLanguages()和GetAllClassificationLevels()已包含外键表.因此，两者都调用相同的2个表.

GetAllClassificationLevelLanguages() and GetAllClassificationLevels() already include the foreign key tables. Thus both call the same 2 tables.

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