我正在为一些看似基本的操作而苦苦挣扎。
假设我有一个名为 Master 的类：
public class Master
{
public Master()
{
Children = new List<Child>();
}
public int Id { get; set; }
public string SomeProperty { get; set; }
[ForeignKey("SuperMasterId")]
public SuperMaster SuperMaster { get; set; }
public int SuperMasterId { get; set; }
public ICollection<Child> Children { get; set; }
}
public class Child
{
public int Id { get; set; }
public string SomeDescription { get; set; }
public decimal Count{ get; set; }
[ForeignKey("RelatedEntityId")]
public RelatedEntity RelatedEntity { get; set; }
public int RelatedEntityId { get; set; }
[ForeignKey("MasterId")]
public Master Master { get; set; }
public int MasterId { get; set; }
}
我们有一个像这样的控制器操作：
public async Task<OutputDto> Update(UpdateDto updateInput)
{
// First get a real entity by Id from the repository
// This repository method returns:
// Context.Masters
// .Include(x => x.SuperMaster)
// .Include(x => x.Children)
// .ThenInclude(x => x.RelatedEntity)
// .FirstOrDefault(x => x.Id == id)
Master entity = await _masterRepository.Get(input.Id);
// Update properties
entity.SomeProperty = "Updated value";
entity.SuperMaster.Id = updateInput.SuperMaster.Id;
foreach (var child in input.Children)
{
if (entity.Children.All(x => x.Id != child.Id))
{
// This input child doesn't exist in entity.Children -- add it
// Mapper.Map uses AutoMapper to map from the input DTO to entity
entity.Children.Add(Mapper.Map<Child>(child));
continue;
}
// The input child exists in entity.Children -- update it
var oldChild = entity.Children.FirstOrDefault(x => x.Id == child.Id);
if (oldChild == null)
{
continue;
}
// The mapper will also update child.RelatedEntity.Id
Mapper.Map(child, oldChild);
}
foreach (var child in entity.Children.Where(x => x.Id != 0).ToList())
{
if (input.Children.All(x => x.Id != child.Id))
{
// The child doesn't exist in input anymore, mark it for deletion
child.Id = -1;
}
}
entity = await _masterRepository.UpdateAsync(entity);
// Use AutoMapper to map from entity to DTO
return MapToEntityDto(entity);
}
现在是存储库方法（MasterRepository）：
public async Task<Master> UpdateAsync(Master entity)
{
var superMasterId = entity.SuperMaster.Id;
// Make sure SuperMaster properties are updated in case the superMasterId is changed
entity.SuperMaster = await Context.SuperMasters
.FirstOrDefaultAsync(x => x.Id == superMasterId);
// New and updated children, skip deleted
foreach (var child in entity.Children.Where(x => x.Id != -1))
{
await _childRepo.InsertOrUpdateAsync(child);
}
// Handle deleted children
foreach (var child in entity.Children.Where(x => x.Id == -1))
{
await _childRepo.DeleteAsync(child);
entity.Children.Remove(child);
}
return entity;
}
最后，来自ChildrenRepository的相关代码：
public async Task<Child> InsertOrUpdateAsync(Child entity)
{
if (entity.Id == 0)
{
return await InsertAsync(entity, parent);
}
var relatedId = entity.RelatedEntity.Id;
entity.RelatedEntity = await Context.RelatedEntities
.FirstOrDefaultAsync(x => x.Id == relatedId);
// We have already updated child properties in the controller method
// and it's expected that changed entities are marked as changed in EF change tracker
return entity;
}
public async Task<Child> InsertAsync(Child entity)
{
var relatedId = entity.RelatedEntity.Id;
entity.RelatedEntity = await Context.RelatedEntities
.FirstOrDefaultAsync(x => x.Id == relatedId);
entity = Context.Set<Child>().Add(entity).Entity;
// We need the entity Id, hence the call to SaveChanges
await Context.SaveChangesAsync();
return entity;
}
The Context财产实际上是DbContext并且事务在操作过滤器中启动。如果操作引发异常，操作过滤器将执行回滚，如果没有，则调用 SaveChanges。
发送的输入对象如下所示：
{
"someProperty": "Some property",
"superMaster": {
"name": "SuperMaster name",
"id": 1
},
"children": [
{
"relatedEntity": {
"name": "RelatedEntity name",
"someOtherProp": 20,
"id": 1
},
"count": 20,
"someDescription": "Something"
}],
"id": 10
}
The Masters表当前有一条 ID 为 10 的记录。它没有子项。
抛出的异常是：
Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: Database operation expected to affect 1 row(s) but actually affected 0 row(s). Data may have been modified or deleted since entities were loaded.
这里发生了什么？我认为 EF 应该跟踪更改，其中包括知道我们在该内部方法中调用了 SaveChanges。
EDIT删除对 SaveChanges 的调用不会改变任何内容。另外，在观察 SQL Server Profiler 中发生的情况时，我找不到 EF 生成的任何 INSERT 或 UPDATE SQL 语句。
EDIT2调用 SaveChanges 时有 INSERT 语句，但仍然没有 Master 实体的 UPDATE 语句。
