通用庫代碼第一和更新文章用新的圖像

Question

我使用一個通用的存儲庫來管理數據庫方面如下：

public abstract class GenericRepository<C, T> : IGenericRepository<T> 
    where T : class 
    where C : ApplicationDbContext, new() 
    { 
    protected C _entities = new C(); 
    public C Context 
    { 
     get { return _entities; } 
     set { _entities = value; } 
    } 

    public void Add(T entity) 
    { 
     _entities.Set<T>().Add(entity); 
    } 

    public void Edit(T entity) 
    { 
     _entities.Entry(entity).State = System.Data.Entity.EntityState.Modified; 
    } 

    public void Save() 
    { 
     _entities.SaveChanges(); 
    } 

    public IQueryable<T> GetAll(string includes) 
    { 
     IQueryable<T> query = _entities.Set<T>(); 
     foreach (var item in includes.Split(new []{','},StringSplitOptions.RemoveEmptyEntries)) 
     query = query.Include(item); 

     return query; 
    } 

    // other methods 
    } 

在我的模型

我有NewsArticle實體：

public class NewsArticle 
    { 
    public int ID { get; set; } 

    public Image Image { get; set; } 

    // some other properties 
    } 

和圖像實體：

public class Image 
    { 
    public int ID { get; set; } 

    public string URL { get; set; } 

    // some other properties 
    } 

來管理NewsArticle我有以下的存儲庫：

public class NewsArticleRepository:GenericRepository<ApplicationDbContext,NewsArticle>,INewsArticleRepository 
    { 
    public NewsArticle Get(int id) 
    { 
     return GetAll("Image,Comments,Tags").FirstOrDefault(x => x.ID.Equals(id)); 

    } 
    } 

所以，當我創建一個新的文章，在NewsArticleController：

[Authorize] 
    [HttpPost] 
    [ValidateAntiForgeryToken] 
    public ActionResult Create([Bind(Include = "Title,Body,SubTitle,Published,ImageUpload,Priority")]GatorsWebSite.ViewModels.NewsArticleViewModel newsArticle) 
    { 
     if (ModelState.IsValid) 
     { 
     var article = new NewsArticle() 
     { 
      Title = newsArticle.Title, 
      SubTitle = newsArticle.SubTitle, 
      Date = DateTime.Now, 
      AuthorID = User.Identity.GetUserId(), 
      Body = newsArticle.Body, 
      Priority = newsArticle.Priority, 
      Published = newsArticle.Published 

     }; 

     if (Request.Files != null && Request.Files.Count > 0 && Request.Files[0].ContentLength > 0) 
      AttachPostedImage(article); 

     UpdateSlideShowQueue(article); 

     _repository.Add(article); 
     _repository.Save(); 
     return RedirectToAction("Index"); 
     } 

     return View(newsArticle); 
    } 

其中AttachPostedImage(article)是：

private void AttachPostedImage(NewsArticle article) 
    { 
     var urlFile = string.Empty; 
     var fileName = Guid.NewGuid().ToString(); 
     var basePath = Server.MapPath("~/Repository/"); 


     if (Request.Files[0].FileName != string.Empty) 
     fileName = Request.Files[0].FileName; 

     urlFile = string.Format("{0}{1}", basePath, fileName); 
     Request.Files[0].SaveAs(urlFile); 
     Image img = new Image() 
     { 
     Title = fileName, 
     URL = string.Format("/Repository/{0}", fileName), 
     Subtitle = string.Empty 
     }; 

     article.Image = img; 

    } 

一切都很好，但是當我嘗試更新與NewsArticle有圖像或沒有圖像的新圖像：

[Authorize] 
    [HttpPost] 
    [ValidateAntiForgeryToken] 
    public ActionResult Edit([Bind(Include = "ID,Title,Body,SubTitle,AuthorID,Date,Published,ImageUpload,Priority")] GatorsWebSite.ViewModels.NewsArticleViewModel newsArticle) 
    { 
     if (!ModelState.IsValid) 
     return View(newsArticle); 

      var article = new NewsArticle() 
     { 
     Title = newsArticle.Title, 
     SubTitle = newsArticle.SubTitle, 
     Date = DateTime.Now, 
     AuthorID = User.Identity.GetUserId(), 
     Body = newsArticle.Body, 
     Priority = newsArticle.Priority, 
     Published = newsArticle.Published 

     }; 

     if (Request.Files != null && Request.Files.Count > 0 && Request.Files[0].ContentLength > 0) 
     AttachPostedImage(article); 

     _repository.Edit(article); 
     _repository.Save(); 
     return RedirectToAction("Index"); 
    } 

在倉庫中的SaveChanges我：

類型的異常 'System.Data.Entity.Infrastructure.DbUpdateConcurrencyException' 發生在EntityFramework.dll但在用戶代碼中沒有處理

ADO.NET:Execute NonQuery "UPDATE [dbo].[NewsArticles] 
SET [Title] = @0, [Body] = @1, [SubTitle] = NULL, [AuthorID] = @2, [Date] = @3, [Published] = @4, [Priority] = @5 
WHERE ([ID] = @6) 
" 
The command text "UPDATE [dbo].[NewsArticles] 
SET [Title] = @0, [Body] = @1, [SubTitle] = NULL, [AuthorID] = @2, [Date] = @3, [Published] = @4, [Priority] = @5 
WHERE ([ID] = @6) 
" was executed on connection "Server=.\SQLEXPRESS;Database=Gators;Integrated Security=True;", returning the number of rows affected. 
Time: 9/12/2014 12:08:46 PM 
Thread:Worker Thread[8524] 

Exception:Thrown: "Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries." (System.Data.Entity.Core.OptimisticConcurrencyException) 
A System.Data.Entity.Core.OptimisticConcurrencyException was thrown: "Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries." 
Time: 9/12/2014 12:08:46 PM 
Thread:Worker Thread[8524] 

我在更新NewsArticle和相關圖像實體時做了什麼錯誤？

Answer 1

您正在將實體狀態設置爲已修改，然後試圖執行並更新，但您沒有爲ID設置值，該值大概是一個int值，因此它試圖對新聞文章進行更新ID爲0.您需要正確設置ID。