我在Generic Repository中插入和更新有问题，在通用插入或更新中它没有问题，但是在很多很多关系中我在插入时遇到错误：
IEntityChangeTracker的多个实例无法引用实体对象。
更新
无法定义两个对象之间的关系，因为它们附加到不同的ObjectContext对象。
我的代码是
接口
public interface IGenericRepository<TEntity>:IDisposable
{
void Insert(TEntity entity);
void Update(TEntity entity);
}
通用类
public class GenericRepository<TEntity> : IGenericRepository<TEntity> where TEntity : class
{
private ApplicationDbContext context=null;
private DbSet<TEntity> dbSet=null;
public GenericRepository()
{
this.context = new ApplicationDbContext();
this.dbSet = context.Set<TEntity>();
}
public GenericRepository(ApplicationDbContext context)
{
this.context = context;
this.dbSet = context.Set<TEntity>();
}
public virtual void Insert(TEntity entity)
{
Error is here---> this.context.Set<TEntity>().Add(entity);
// dbSet.Add(entity);
context.SaveChanges();
}
public virtual void Update(TEntity entity)
{
Error is here---> dbSet.Attach(entity);
context.Entry(entity).State = EntityState.Modified;
context.SaveChanges();
}
}
和控制代码
private IGenericRepository<Blog> _Repository = null;
private IGenericRepository<BlogTag> _RepositoryTag = null;
private IGenericRepository<BlogCategory> _RepositoryCategory = null;
public BlogsController()
{
this._Repository = new GenericRepository<Blog>(new DbContext());
this._RepositoryTag = new GenericRepository<BlogTag>(new DbContext());
this._RepositoryCategory = new GenericRepository<BlogCategory>(new DbContext());
}
public async Task<ActionResult> Create([Bind(Include = "BlogID,BlogTitle,BlogContent,VisitCount,Preview")] Blog blog
,string[] SelectedTags,string[] SelectedCategories, HttpPostedFileBase files)
{
if (SelectedTags != null)
{
blog.BlogTags = new List<BlogTag>();
foreach (var tag in SelectedTags)
{
var tagToAdd = _RepositoryTag.GetById(int.Parse(tag));
blog.BlogTags.Add(tagToAdd);
}
}
if (SelectedCategories != null)
{
blog.BlogCategories = new List<BlogCategory>();
foreach (var cat in SelectedCategories)
{
var catToAdd = _RepositoryCategory.GetById(int.Parse(cat));
blog.BlogCategories.Add(catToAdd);
}
}
if (ModelState.IsValid)
{
blog.DateTimeInsert = DateTime.UtcNow;
blog.DateTimeModify = DateTime.UtcNow;
blog.ImagePath= files != null ? Path.GetFileName(files.FileName) : "";
blog.BlogContent = HttpUtility.HtmlEncode(blog.BlogContent);
_Repository.Insert(blog);
return RedirectToAction("Index");
}
ViewBag.BlogTags = new SelectList(_RepositoryTag.Get(), "BlogTagID", "TagName");
ViewBag.BlogCategories = new SelectList(_RepositoryCategory.Get(), "BlogCategoryID", "CategoriesName");
return View(blog);
}
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Edit([Bind(Include = "BlogID,BlogTitle,BlogContent,VisitCount,Preview")] Blog blog
, string[] SelectedTags, string[] SelectedCategories, HttpPostedFileBase files)
{
if (Request["BlogID"] == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
int id = int.Parse(Request["BlogID"].ToString());
var blogsToUpdate = _Repository.Query(i => i.BlogID == id, null).Include(t => t.BlogTags).Include(t => t.BlogCategories).Single();
if (TryUpdateModel(blogsToUpdate, "",
new string[] { "BlogID", "BlogTitle", "BlogContent", "VisitCount","Preview" }))
{
try
{
UpdateInstructorCourses(SelectedTags, SelectedCategories, blogsToUpdate);
blogsToUpdate.DateTimeModify = DateTime.UtcNow;
blogsToUpdate.DateTimeInsert = DateTime.UtcNow;
blogsToUpdate.BlogContent = HttpUtility.HtmlEncode(blogsToUpdate.BlogContent);
await _Repository.UpdateAsync(blogsToUpdate, d => d.BlogTitle, d => d.VisitCount, d => d.BlogContent, d => d.ImagePath);
return RedirectToAction("Index");
}
catch (RetryLimitExceededException /* dex */)
{
//Log the error (uncomment dex variable name and add a line here to write a log.
ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists, see your system administrator.");
}
}
AssignedDDLCHKBoxValues(blogsToUpdate);
return View(blogsToUpdate);
}
private void UpdateInstructorCourses(string[] SelectedTags, string[] SelectedCategories, Blog blogsToUpdate)
{
if (SelectedTags == null)
{
blogsToUpdate.BlogTags = new List<BlogTag>();
return;
}
if (SelectedCategories == null)
{
blogsToUpdate.BlogCategories = new List<BlogCategory>();
return;
}
var SelectedTagsHS = new HashSet<string>(SelectedTags);
var SelectedCategoriesHS = new HashSet<string>(SelectedCategories);
var blogTags = new HashSet<int>(blogsToUpdate.BlogTags.Select(c => c.BlogTagID));
foreach (var tag in _RepositoryTag.Get())
{
if (SelectedTagsHS.Contains(tag.BlogTagID.ToString()))
{
if (!blogTags.Contains(tag.BlogTagID))
{
blogsToUpdate.BlogTags.Add(tag);
}
}//if
else
{
if (blogTags.Contains(tag.BlogTagID))
{
blogsToUpdate.BlogTags.Remove(tag);
}
}//else
}//foreach tag
var blogcategories = new HashSet<int>
(blogsToUpdate.BlogCategories.Select(c => c.BlogCategoryID));
foreach (var Category in _RepositoryCategory.Get())
{
if (SelectedCategoriesHS.Contains(Category.BlogCategoryID.ToString()))
{
if (!blogcategories.Contains(Category.BlogCategoryID))
{
blogsToUpdate.BlogCategories.Add(Category);
}
}//if
else
{
if (blogcategories.Contains(Category.BlogCategoryID))
{
blogsToUpdate.BlogCategories.Remove(Category);
}
}//else
}//foreach skill
}
答案 0 :(得分：0)
您的问题是您使用多个上下文来处理单个实体。 在您的控制器构造函数上，您有以下这些行：
this._Repository = new GenericRepository<Blog>(new DbContext());
this._RepositoryTag = new GenericRepository<BlogTag>(new DbContext());
this._RepositoryCategory = new GenericRepository<BlogCategory>(new DbContext());
在这里，您将创建3个应该一起工作的存储库9，具有3种不同的上下文。
之后，继续阅读RepositoryTag存储库，这里：
var tagToAdd = _RepositoryTag.GetById(int.Parse(tag));
执行此操作时，对象tagToAdd将附加到RepositoryTag内的上下文。如果您调试列表BlogTags，在其中添加此tagToAdd，您将看到您拥有动态代理，这意味着该对象已附加到上下文。
之后，您可以使用另一个上下文来填充存储库类别：
var catToAdd = _RepositoryCategory.GetById(int.Parse(cat));
blog.BlogCategories.Add(catToAdd);
现在，您的blog对象引用了2个不同的上下文：用于加载标记的上下文（RepositoryTag），以及用于加载博客类别的上下文（{{1} }）。
最后，您尝试将RepositoryCategory usgin用于第三个上下文：
blog这将引发异常，因为EF无法使用这样的多个上下文。
要解决此问题，只需在存储库之前实例化上下文，并将其传递给所有yout存储库，如下所示：
_Repository.Insert(blog);
现在，不要忘记你应该处理你的情境。这就是为什么最推荐和最常用的方法是使用这样的代码：
this.context = new DbContext(); // The context you need to use for all operations you are performing here.
this._Repository = new GenericRepository<Blog>(this.context);
this._RepositoryTag = new GenericRepository<BlogTag>(this.context);
this._RepositoryCategory = new GenericRepository<BlogCategory>(this.context);