无法使用实体框架和ASP.NET Core 2查询图像表

Question

我正在尝试通过ajax查询我的帖子表以显示在前端。

这是我的查询：

[HttpGet]
public JsonResult GetGalleryLocations()
{
    var data = _context.Posts
       .Include(c => c.Category)
       .ToList();

    return Json(data);
}

然后在我的前端，我得到这样的：

 $.ajax({
      url: "@Url.Action("GetGalleryLocations", "Home")",
      type: "GET",
      data: {
          title: '',
          lat: '',
          lng: '',
          images: []
      },
      success: function (data) {
          data.forEach(function (element) {
              $("#ajaxAppendDIV").append(
                 // Append HTML here
              );
          });
      }      
});

这就是我回复的内容：

每个帖子都有很多与之相关的图片，所以我需要做这样的查询;

[HttpGet]
public JsonResult GetGalleryLocations()
{
    var data = _context.Posts
       .Include(c => c.Category)       
       .Include(c => c.Images) 
       .ToList();

    return Json(data);
}

但是当我执行这个查询时，我会回来：qazxsw poi

这是我两个模型之间的关系：Post model

图像型号：

 public class Post
    {
        public int Id { get; set; }     
        public string Title { get; set; }
        public double Lat { get; set; }
        public double Lng { get; set; }
        public DateTime Created { get; set; }
        public Category Category { get; set; }
        public int CategoryId { get; set; }

        public IEnumerable<Image> Images { get; set; }

        // .....
    }

当我在查询中使用图像模型执行Include（）语句时，我不明白为什么它会破坏？

仅供参考，我将在我的视图中调用以获取帖子的第一张图片：

 public class Image
{
    public int Id { get; set; }
    public string FileName { get; set; }

    public Post Post { get; set; }
    public int PostId { get; set; }
}

每个循环的查询将与我显示的相同

/ *********更新*********** /

我将Post模型初始化为：

@foreach (var gallery in Model)
{
  <img src="@gallery.Images.First().FileName" />
}

这就是我现在试图加载它的方式：

public class Post
{

  public Post()
  {
      Images = new List<Image>();
  }

   public int Id { get; set; }   
   // .....

   public List<Image> Images { get; set; }

}

Answer 1

在我们讨论之后，我相信你的问题就是你在对象图中没有创建的参考类型。我希望这有效:)。它从一个post控制器开始，你的viewmodel开始模拟bind。

Answer 2

我弄清楚问题是什么。

我不得不在public void ConfigureServices方法中将它添加到我的Startup.cs类中：

 public IActionResult Post(PostViewModel pvm)
//objects to save in our db context
Post post = new Post()

//collection objects we will fill the list in below

Tag tag = new Tag();
Image img = new Image();

//these lists will pass the value of pvm.tags List and pvm.Images List
// To our post object

List<Images> ImgHolderList = new List<Images>();
List<Tags> TagHolderList = new List<Tags>();

//bind properties from vm if pvm is valid
if(!ModelState.IsValid){

return BadRequest("error");
}


//... Know add image and tag objects to to our empty holder Collections
ImgHolderList = pvm.Images;//---------> this is where I think the null was comming ftm
TagHolderList = pvm.Tagsl

//bind properties from vm if pvm is valid
if(ImgHolderList == null || TagHolderList == null){

return NoContent();
}

Post.Images = ImageHolderList;//---------> this is where I think the null was comming ftm
Post.Tags = TagHolderList;//---------> this is where I think the null was comming ftm

//---------better to use some design/mapper but for simplicity bind model here
//...add all other properties

post.primitives = pvm.Id;
post.primitives = pvm.Lat

//.......

// know our object graph is full hopefully

   context.Posts.Add(Image1);


                context.SaveChanges();

return Ok;
}




know you want to Get this collection very simple

[Produces("application/json")] //with this your api controller returns json with OK()
    [Route("api/GetAll")]
    public class GetAllController : Controller
    {
    private readonly ApiContext ctx = ApiContext.db; // OR use DI

   // GET api/values
        [HttpGet]
        public IActionResult Get()
        {
            var x = ctx.Posts.Include(x => x.Images).Include(x => x.Tags)ToList();
            return Ok(x.ToList());
        }

我从这个

public void ConfigureServices(IServiceCollection services)
{
    // Other services here.....

    services.AddMvc().AddJsonOptions(options => {
        options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
    });
}

得到了这个

我稍稍调整了我的模型：

post on stackoverflow

保持我的Image模型一样。

这是我为我的Images数组得到的，这就是我想要的：

public class Post
{
      public Post()
      {
          Images = new List<Image>();
      }

      // Other attributes here...

      public ICollection<Image> Images { get; set; }
}

然后，我只是将图像附加到：