我有一个包含图像实体集合的食谱实体。在我的控制器中，我尝试保存一个附有两个新图像的新配方：
_recipeService.Insert(recipe);
try
{
foreach (Image img in recipe.Images)
{
_imageService.Update(img);
}
_recipeService.Save();
在后台，我使用工作单元模式来确保所有服务都使用相同的 DbContext，并且在任何服务上调用 Save() 都会保存所有实体。因此，如果我在创建过程中将两个图像附加到我的食谱中，我会在尝试保存时收到以下错误：
AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges.
我确定这与两个图像实体的 ID 均为 0 的事实有关。这里的最佳做法是什么？
FWIW，这是我的初始迁移：
public override void Up()
{
CreateTable(
"dbo.Recipe",
c => new
{
ID = c.Int(nullable: false, identity: true),
CategoryId = c.Int(nullable: false),
Title = c.String(),
Summary = c.String(),
Directions = c.String(),
CookingTime = c.Int(nullable: false),
CreationDate = c.DateTime(nullable: false),
PostedDate = c.DateTime(),
LastModifiedDate = c.DateTime(nullable: false),
Visible = c.Boolean(nullable: false),
TagList = c.String(),
Ingredient_ID = c.Int(),
})
.PrimaryKey(t => t.ID)
.ForeignKey("dbo.Category", t => t.CategoryId, cascadeDelete: true)
.ForeignKey("dbo.Ingredient", t => t.Ingredient_ID)
.Index(t => t.CategoryId)
.Index(t => t.Ingredient_ID);
CreateTable(
"dbo.Image",
c => new
{
ID = c.Int(nullable: false, identity: true),
RecipeId = c.Int(nullable: false),
ImageUrl = c.String(nullable: false),
MainImage = c.Boolean(nullable: false),
})
.PrimaryKey(t => t.ID)
.ForeignKey("dbo.Recipe", t => t.RecipeId, cascadeDelete: true)
.Index(t => t.RecipeId);
谢谢，
克里斯
编辑：为配方服务添加代码
使用 Barbecurian.Data；使用 Barbecurian.Models；使用系统；使用 System.Collections.Generic；使用 System.Linq；使用 System.Web；
public class RecipeService : Service<Recipe>
{
private IService<Tag> _tagService;
public RecipeService(IUnitOfWork unitOfWork, IService<Tag> tagService)
{
_unitOfWork = unitOfWork;
_tagService = tagService;
_repo = _unitOfWork.RecipeRepository;
}
public override void Insert(Recipe recipeToCreate)
{
List<Tag> tags = new List<Tag>();
foreach (Tag tag in recipeToCreate.Tags)
{
if (_tagService.Get(filter: t => t.Name == tag.Name).Count() > 0)
{
tags.Add(_tagService.Get(filter: t => t.Name == tag.Name).SingleOrDefault());
}
else
{
Tag newTag = new Tag() {
Name = tag.Name
};
_tagService.Insert(newTag);
tags.Add(newTag);
}
}
recipeToCreate.Tags = tags;
// Validation logic
if(Validate(recipeToCreate))
_repo.Insert(recipeToCreate);
}
protected override bool Validate(Recipe recipeToValidate)
{
//Ensure recipe has a unique title
if (_repo.Get(r => r.Title == recipeToValidate.Title).Count() > 0)
_validationState.AddError("Title", "That title already exists.");
return _validationState.IsValid;
}
}
}
这继承自：
public abstract class Service<TEntity> : IService<TEntity> where TEntity : class, IModel
{
protected IRepository<TEntity> _repo;
protected IValidationDictionary _validationState;
protected IUnitOfWork _unitOfWork;
public virtual IEnumerable<TEntity> Get(Expression<Func<TEntity, bool>> filter = null,
Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
string includeProperties = ""){
return _repo.Get(filter, orderBy, includeProperties);
}
public virtual TEntity GetByID(int id, string includeProperties = ""){
return _repo.GetByID(id, includeProperties);
}
public virtual void Insert(TEntity entity){
_repo.Insert(entity);
}
public virtual void Delete(object id){
_repo.Delete(id);
}
public virtual void Delete(TEntity entity){
_repo.Delete(entity);
}
public virtual void Update(TEntity entity)
{
_repo.Update(entity);
}
public virtual void Save()
{
_unitOfWork.Save();
}
public virtual void Dispose()
{
_unitOfWork.Dispose();
}
protected abstract bool Validate(TEntity entity);
public IValidationDictionary ValidationState
{
get
{
return _validationState;
}
set
{
_validationState = value;
}
}
}
}