Entity Framework "Code supposed to be unreachable" on agrigated include 表达式

Question

第一

我已经创建了这个 GitHub repo 只需按 F5 键就会遇到这个错误 所以你应该很容易尝试这个。此问题中的所有链接都指向该存储库。

代码流

我的控制器中的 following expression code 是我想让前端开发人员包含他们需要的关系的地方。

// The included tables I want to control from my controller
Expression<Func<CompanyDto, object>>[] includes = { x => x.Employees, x => x.Cars };

var companyDto2 = await service.GetByIdAsync(1, includes).ConfigureAwait(false);

然后在我的服务层I map the dto includes to my entity includes并将它们发送到存储库

var entityIncludes = mapper.Map<Expression<Func<Entity, object>>[]>(includes);

var result = await repository.GetByIdAsync(id, entityIncludes).ConfigureAwait(false);

错误

当我运行在我的 repository 中包含表达式时，出现以下错误。

"Code supposed to be unreachable"

这里有 两个例子 我试过的抛出这个错误的东西。

第一次尝试

这是 enter link description here

的尝试

var queryableResultWithIncludes = includes
.Aggregate(dbContext.Set<TEntity>().AsQueryable(),
(current, include) => current.Include(include));

// return the result of the query using the specification's criteria expression
var result = queryableResultWithIncludes.AsEnumerable();

// Here we get "Code supposed to be unreachable"
var neverHappens = result .ToList();

第二次尝试

// Second attempts
if (includes.Length > 0)
{
    IQueryable<TEntity> set = includes
       .Aggregate<Expression<Func<TEntity, object>>, IQueryable<TEntity>>
       (dbContext.Set<TEntity>(), (current, expression) => current.Include(expression));

    // Here we also get "Code supposed to be unreachable"
    return await set.SingleOrDefaultAsync(s => s.Id == id).ConfigureAwait(false);
}

总结

我错过了什么？我在做某种反模式的事情吗？我需要一些 EF 专家告诉我:-)

Answer 1

正如我所怀疑的那样，这个问题与 EF 没有任何共同之处，而是 AutoMapper 表达式翻译产生的无效表达式：

var entityIncludes = mapper.Map<Expression<Func<Entity, object>>[]>(includes);

可以通过扩展 Locals/Watch window 中的 entityIncludes 变量来查看 - 您将在调试视图或 Parameters [=33= 中看到有问题的异常] LambdaExpression.

话虽如此，问题是由不正确的 AutoMapper 配置引起的，特别是缺少 AddExpressionMapping()。您为 AutoMapper 全局配置执行了此操作，但您的代码正在使用依赖注入，因此您需要在那里执行此操作，例如

当前

services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());
// Auto Mapper Configurations
AutoMapper.Mapper.Initialize(cfg =>
{
    cfg.DisableConstructorMapping();
    cfg.AddExpressionMapping();
    cfg.AddProfile<CompanyProfile>();
});

应该是

services.AddAutoMapper(cfg =>
{
    cfg.DisableConstructorMapping();
    cfg.AddExpressionMapping();    
}, AppDomain.CurrentDomain.GetAssemblies());

Entity Framework "Code supposed to be unreachable" on agrigated include 表达式

Entity Framework "Code supposed to be unreachable" on agrigated include expression

c#

lambda

entity-framework

repository-pattern

entity-framework-core