postgresql - EF Core 2.0 更新 - 跟踪问题

Question

我正在从前端获取更改的实体，将其映射到后端，并且只想在数据库中更新它。更新执行如下:

[HttpPut("{id}")]
    public IActionResult Update(string id, [FromBody]Worker worker)
    {
        using (var dbContext= new MyDbContext())
        {
            dbContext.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;

            var entity = dbContext.Workers.FirstOrDefault(r => r.Id == worker.Id);

            if (entity == null) return BadRequest();

            dbContext.Workers.Update(worker);
            dbContext.SaveChanges();
            return Ok();
        }}

在此操作之前，我正在获取用户列表并将其发送到前端。尽管我将 QueryTrackingBehavior 设置为 NoTracking，但出现异常:

System.InvalidOperationException: 'The instance of entity type 'Contract' cannot be tracked because another instance with the key value 'Id:4' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.'

Contract 是更新的 Worker 的相关实体...

知道我在这里做错了什么吗？

更新:

worker -契约(Contract)关系:

   public class Worker: IId
{
    public int Id { get; set; }
    public ICollection<Contract> Contracts{ get; set; }
}
 public class Contract: IId
{
    public int Id { get; set; }
    public int WorkerId { get; set; }
    public Worker Worker { get; set; }
}

Answer 1

好的!在您的代码中遇到问题。您没有将更新的实体映射到您从数据库中提取的现有实体。您必须将更新的实体映射到现有实体。为此，您可以使用 AutoMapper 或如下显式映射:

您可以按如下方式解决问题:

[HttpPut("{id}")]
public IActionResult Update(string id, [FromBody]Worker worker)
{
        using (var dbContext= new MyDbContext())
        {
            var entityToBeUpdated = dbContext.Workers.AsNoTracking().FirstOrDefault(r => r.Id == worker.Id);

            if (entity == null) return BadRequest();

            entityToBeUpdated.Property1 = worker.Property1;
            entityToBeUpdated.Property2 = worker.Property2;
            // Do the same for the other changed properties as well

            dbContext.Workers.Update(entityToBeUpdated);
            dbContext.SaveChanges();
            return Ok();
        }
 }

或者您可以尝试如下操作:

[HttpPut("{id}")]
public IActionResult Update(string id, [FromBody]Worker worker)
{
      using (var dbContext= new MyDbContext())
      {
           var entityToBeUpdated = dbContext.Workers.FirstOrDefault(r => r.Id == worker.Id);

           if (entity == null) return BadRequest();

           entityToBeUpdated.Property1 = worker.Property1;
           entityToBeUpdated.Property2 = worker.Property2;
           // Do the same for the other changed properties as well.

           dbContext.SaveChanges();
           return Ok();
      }
}