具有 AutoMapper 抛出异常的通用工作单元和存储库模式 "another entity of the same type already has the same primary key value"

Question

我将以下 GitHub 项目用于通用存储库和 UoW 模式

https://genericunitofworkandrepositories.codeplex.com/

    [HttpPost]
    [Route("update")]
    public HttpResponseMessage Update(HttpRequestMessage request, ComponentViewModel component)
    {
        return CreateHttpResponse(request, () =>
        {
            HttpResponseMessage response = null;

            if (!ModelState.IsValid)
            {
                response = request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
            else
            {
                var componentDb = UnitOfWork.Repository<Component>().Find(component.ID);

                if (componentDb == null)
                    response = request.CreateErrorResponse(HttpStatusCode.NotFound, "Invalid component.");
                else
                {
                    componentDb = Mapper.Map<ComponentViewModel, Component>(component);
                    UnitOfWork.Repository<Component>().Update(componentDb); // <-- ERROR'S HERE

                    UnitOfWork.SaveChanges();
                    response = request.CreateResponse<ComponentViewModel>(HttpStatusCode.OK, component);
                }
            }

            return response;
        });
    }

我在 UnitOfWork.Repository<Component>().Update(componentDb);

得到以下异常

Attaching an entity of type 'Component' failed because another entity of the same type already has the same primary key value

我认为这是由于它之前的 AutoMapper Mapper.Map 代码造成的，但是，我不确定如何更正它。

请告知如何更正用法。

Answer 1

那是因为你使用的是Find方法。此方法会将返回的实体附加到您的上下文，稍后使用 Automapper 您将创建一个断开连接的 POCO 实体，稍后您将尝试使用通用存储库的 Update 方法将其附加到您的上下文，并且两个实体共享同样的Id。使用 Any 扩展方法而不是 Find 来检查您的 table 中是否存在具有 Id 的实体：

 if (UnitOfWork.Repository<Component>().Any(c=>c.Id==component.ID))// Call Any here
 {
       componentDb = Mapper.Map<ComponentViewModel, Component>(component);
       UnitOfWork.Repository<Component>().Update(componentDb); 
       UnitOfWork.SaveChanges();
       response = request.CreateResponse<ComponentViewModel>(HttpStatusCode.OK, component);
 }
 else
 {
      response = request.CreateErrorResponse(HttpStatusCode.NotFound, "Invalid component.");
 }

具有 AutoMapper 抛出异常的通用工作单元和存储库模式 "another entity of the same type already has the same primary key value"

Generic UnitofWork & Repository pattern with AutoMapper throwing exception "another entity of the same type already has the same primary key value"

c#

entity-framework

automapper

repository-pattern

unit-of-work