c# - EF Core 已跟踪具有相同 id 的实体

Question

我不知道如何消除该错误:

The instance of entity type 'Relation' cannot be tracked because another instance with the key value '{Id: 26}' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.

我尝试将实体与上下文分离，但即使这样也无法阻止此错误的发生。有人可以指出我做错了什么吗？

服务:

private async Task<int> EditAsync(RelationModel model)
{
    RelationEntity entity = _mapper.ToEntity(model);
    RelationEntity oldRelation = await _relationRepository.GetRelationAsync(entity.Id);
    _relationRepository.UpdateRelation(oldRelation, entity);
    await _relationRepository.SaveAsync();
    return entity.Id;
}

存储库:

    public void UpdateRelation(Relation oldRelation, Relation relation)
    {
        if (oldRelation != null)
        {
            // Detach
            Context.Entry(oldRelation).State = EntityState.Detached;

            // Delete childs
            if (oldRelation.Person != null && relation.Person == null)
            {
                Context.Persons.Remove(oldRelation.Person);
            }

            if (oldRelation.Customer != null && relation.Customer == null)
            {
                Context.Customers.Remove(oldRelation.Customer);
            }

            if (oldRelation.Supplier != null && relation.Supplier == null)
            {
                Context.Suppliers.Remove(oldRelation.Supplier);
            }

            if (oldRelation.Employee != null && relation.Employee == null)
            {
                Context.Employees.Remove(oldRelation.Employee);
            }

            // Update parent
            Context.Relations.Update(relation); // <-- error occurs
        }
    }

关系实体:

public class Relation : BaseEntity<int>
{
    public string Code { get; set; }

    public int? PersonId { get; set; }
    public Person Person { get; set; }

    public int? CompanyId { get; set; }
    public Company Company { get; set; }

    public int? CustomerId { get; set; }
    public Customer Customer { get; set; }

    public int? SupplierId { get; set; }
    public Supplier Supplier { get; set; }

    public int? EmployeeId { get; set; }
    public Employee Employee { get; set; }

    public ICollection<RelationRelations> ParentRelations { get; set; }
    public ICollection<RelationRelations> ContactPersons { get; set; }
    public ICollection<RelationContactMethod> ContactMethods { get; set; }
    public ICollection<RelationAddress> Addresses { get; set; }
}

更新

我尝试更换

Context.Relations.Update(relation); 

与

Context.Entry(oldRelation).CurrentValues.SetValues(relation);

但是 Relation 实体上的所有属性都没有得到更新。

更新2

运行以下代码时

Context.Entry(oldRelation).CurrentValues.SetValues(relation);
Context.SaveChanges();

我可以看到旧关系已使用新值进行更新，但它们并未应用于数据库...这是为什么？

Answer 1

我多年来一直使用此代码而不是“更新”，所有内容总是正确更新，并且从未出现过任何错误。

尝试对 EF 使用通用代码从来都不是一个好主意。如果您想更新多个类，请尝试选择这种方式:

 var oldrelation = Context.Relations
.Include(i=> i.Person)
.Include(i=> i.Company)
...
.FirstOrDefault(i=> i.Id=entity.Id);

替换

 Context.Relations.Update(relation); 

与

Context.Entry(oldRelation).CurrentValues.SetValues(relation);