MVC EF - 更新导航属性 [英] MVC EF - Update navigation property

问题描述

您可以在下面看到我的数据库图。

Post.cs

  public partial class Post 
 {
 public Post（）
 {
 this.PostImages = new HashSet< PostImage>（）; 
 this.PostMappings = new HashSet< PostMapping>（）; 
} 
 
 public int ID {get;组; } 
 public string标题{get;组; } 
 public string TitleMenu {get;组; } 
 public string Preview {get;组; } 
 public string Content {get;组; } 
 public Nullable< bool>可见{get;组; } 
 public Nullable< int>显示{get;组; } 
 public Nullable< System.DateTime> DateAdded {get;组; } 
 public Nullable< System.DateTime> DateHide {get;组; } 
 public Nullable< int> PozitionMenu {get;组; } 
 public string Username {get;组; } 
 
 public virtual ICollection< PostImage> PostImages {get;组; } 
 public virtual ICollection< PostMapping> PostMappings {get;组; } 
} 
  

Category.cs

  public partial class Category 
 {
 public Category（）
 {
 this.CourseMappings = new HashSet< CourseMapping>（）; 
 this.PostMappings = new HashSet< PostMapping>（）; 
} 
 
 public int ID {get;组; } 
 public string Name {get;组; } 
 public Nullable< bool>可见{get;组; } 
 public string Color {get;组; } 
 public Nullable< int>显示{get;组; } 
 public Nullable< bool> IsBlog {get;组; } 
 
 public virtual ICollection< CourseMapping> CourseMappings {get;组; } 
 public virtual ICollection< PostMapping> PostMappings {get;组; } 
} 
  

PostMapping.cs

  public partial class PostMapping 
 {
 public System.Guid ID {get;组; } 
 public Nullable< int> PostID {get;组; } 
 public Nullable< int> CategoryID {get;组; } 
 
 public virtual Category Category {get;组; } 
 public virtual Post Post {get;组; 
} 
  

控制器

  public ActionResult Edit（Post post，string [] selectedCategories）
 {
 if（ModelState.IsValid）
 {
 db.Entry post）.State = EntityState.Modified; 
 
 db.SaveChanges（）; 
 return RedirectToAction（Index）; 
} 
 
 return View（post）; 
} 
  

我想用导航属性更新我的帖子 。
参数 selectedCategories 包含带有ids的列表。 （类别ID）

如何更新PostMapping 表？

---

编辑：

如何删除PostMapping对象？
我以这种方式尝试：

  [HttpPost] 
 [ValidateAntiForgeryToken] 
 public ActionResult编辑（Post post，int [] selectedCategories）
 {
 
 
 
 if（ModelState.IsValid）
 {
列表< PostMapping> list_already = db.PostMappings.Where（p => p.PostID == post.ID）.ToList（）; 
 
 
 post.PostMappings = list_already; 
 
 
 foreach（PostMapping pm in list_already）
 {
 int categoryId = pm.CategoryID.Value; 
 if（selectedCategories！= null）
 {
 if（selectedCategories.Contains（categoryId））
 {
 selectedCategories = selectedCategories.Where（val => val！ = categoryId）.ToArray（）; 
} 
} 
 else 
 {
 
 post.PostMappings.Remove（pm）; 
类别category = db.Categories.Where（c => c.ID == categoryId）.SingleOrDefault（）; 
 category.PostMappings.Remove（pm）; 
} 
} 
 
 foreach（selectedCategories中的var id）
 {
类别category = db.Categories.Where（c => c.ID == id）.SingleOrDefault（）; 
 PostMapping postMap = new PostMapping（）; 
 postMap.Category = category; 
 postMap.Post = post; 
 postMap.ID = Guid.NewGuid（）; 
 
 post.PostMappings.Add（postMap）; 
 
 
 category.PostMappings.Add（postMap）; 
 
} 
 
 db.Entry（post）.State = EntityState.Modified; 
 
 
 db.SaveChanges（）; 
 return RedirectToAction（Index）; 
} 
 return View（post）; 
} 
  

解决方案

您创建PostMapping对象：

  foreach（selectedCategories中的string categoryName）
 {
类别category = LoadCategoryForName（categoryName）; 
 PostMapping postMap = new PostMapping（）; 
 postMap.Category = category; 
 postMap.Post = post; 
 //将地图添加到cat和post 
 post.PostMaps.Add（postMap）; 
 category.PostMaps.Add（postMap）; 
} 
 
 //更新db。 
  

只有在创建PostMappimgs并将其放置在正确的位置时，才知道PostMappimgs。 p>

You can see my database diagram below.

Post.cs

public partial class Post
{
    public Post()
    {
        this.PostImages = new HashSet<PostImage>();
        this.PostMappings = new HashSet<PostMapping>();
    }

    public int ID { get; set; }
    public string Title { get; set; }
    public string TitleMenu { get; set; }
    public string Preview { get; set; }
    public string Content { get; set; }
    public Nullable<bool> Visible { get; set; }
    public Nullable<int> Display { get; set; }
    public Nullable<System.DateTime> DateAdded { get; set; }
    public Nullable<System.DateTime> DateHide { get; set; }
    public Nullable<int> PozitionMenu { get; set; }
    public string Username { get; set; }

    public virtual ICollection<PostImage> PostImages { get; set; }
    public virtual ICollection<PostMapping> PostMappings { get; set; }
}

Category.cs

public partial class Category
{
    public Category()
    {
        this.CourseMappings = new HashSet<CourseMapping>();
        this.PostMappings = new HashSet<PostMapping>();
    }

    public int ID { get; set; }
    public string Name { get; set; }
    public Nullable<bool> Visible { get; set; }
    public string Color { get; set; }
    public Nullable<int> Display { get; set; }
    public Nullable<bool> IsBlog { get; set; }

    public virtual ICollection<CourseMapping> CourseMappings { get; set; }
    public virtual ICollection<PostMapping> PostMappings { get; set; }
}

PostMapping.cs

public partial class PostMapping
{
    public System.Guid ID { get; set; }
    public Nullable<int> PostID { get; set; }
    public Nullable<int> CategoryID { get; set; }

    public virtual Category Category { get; set; }
    public virtual Post Post { get; set; }
}

Controller

public ActionResult Edit(Post post, string[] selectedCategories)
{
    if (ModelState.IsValid)
    {          
        db.Entry(post).State = EntityState.Modified;

        db.SaveChanges();
        return RedirectToAction("Index");
    }

    return View(post);
}

I want to update my Post with navigation properties. Parameter selectedCategories contains a list with ids. (category id).

How can I update PostMapping table?

---

Edit:

How can I delete an PostMapping object? I tried in this way:

        [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Edit(Post post, int[] selectedCategories)
    {



        if (ModelState.IsValid)
        {
            List<PostMapping> list_already = db.PostMappings.Where(p => p.PostID == post.ID).ToList();


            post.PostMappings = list_already;


            foreach (PostMapping pm in list_already)
            {
                int categoryId = pm.CategoryID.Value;
                if (selectedCategories != null)
                {
                    if (selectedCategories.Contains(categoryId))
                    {
                        selectedCategories = selectedCategories.Where(val => val != categoryId).ToArray();
                    }
                }
                else
                {

                    post.PostMappings.Remove(pm);
                    Category category = db.Categories.Where(c => c.ID == categoryId).SingleOrDefault();
                    category.PostMappings.Remove(pm);
                }
            }

            foreach (var id in selectedCategories)
            {
                Category category = db.Categories.Where(c => c.ID == id).SingleOrDefault();
                PostMapping postMap = new PostMapping();
                postMap.Category = category;
                postMap.Post = post;
                postMap.ID = Guid.NewGuid();

                post.PostMappings.Add(postMap);


                category.PostMappings.Add(postMap);

            }

            db.Entry(post).State = EntityState.Modified;


            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(post);
    }

解决方案

You create the PostMapping objects:

foreach (string categoryName in selectedCategories)
{
    Category category = LoadCategoryForName(categoryName);
    PostMapping postMap = new PostMapping();
    postMap.Category = category;
    postMap.Post = post;
    // Add the maps to cat and post
    post.PostMaps.Add(postMap);
    category.PostMaps.Add(postMap);
}

// update the db.

EF knows about the PostMappimgs only if you create them, and put them in their proper places.

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