Question

我想问一下如何在我的案例中包括数据。我创建了一个关联表，用于定义BusinessGlosItems之间的关系。在下一步中，我创建了BusinessGlosItems模型，并通过子级和父级关系包括了引用表。

最后，我需要显示BusinessGlosItems的详细信息及其所有关联数据。听起来很简单，但我不知道该如何解决。有人可以帮忙吗？

我的域类如下：

public class BusinessGlosItem
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public string BGIName { get; set; }

    [InverseProperty("ChildBGItem")]
    public ICollection<Reference> ChildReferences { get; set; }
    [InverseProperty("ParentBGItem")]
    public ICollection<Reference> ParentReferences { get; set; }
}

public class Reference
{
    public int Id { get; set; }
    [ForeignKey("ChildBGItem")]
    public int? ChildGlosItemId { get; set; }
    [ForeignKey("ParentBGItem")]
    public int? ParentGlosItemId { get; set; }

    public int ReferenceTypeId { get; set; }

    public virtual ReferenceType ReferenceType { get; set; }

    public virtual BusinessGlosItem ChildBGItem { get; set; }

    public virtual BusinessGlosItem ParentBGItem { get; set; }
}

我想做什么：

@page
@model BusinessGlosItem.DetailsModel

<div>
    <table class="table table-hover">
        <th>Reference Type</th>
        <th>Parent Item Name</th>
        <th>Child Item Name</th>

        @foreach (var item in Model.BusinessGlosItem.ParentReferences)
        {
            <tr>
                <td>@item.ReferenceType.ReferenceTypeName</td>
                <td>@item.ParentBGItem.BGIName</td>
                <td>@item.ChildGlosItemId</td> //Here I would like to see the ChildItem Name
            </tr>
        }
    </table>
</div>

我从视图中得到NullReferenceException: Object reference not set to an instance of an object. on the line。

我的方法是：

public BusinessGlosItem BusinessGlosItem { get; set; }

public async Task<IActionResult> OnGetAsync(int? id)
{
      if (id == null)
      {
                return NotFound();
      }

      BusinessGlosItem = await _context.businessGlosItem                 
                .Include(x => x.BusinessArea)
                .Include(x => x.BusinessGlosItemStatus)
                .Include(x => x.ChildReferences).ThenInclude(x=>x.ReferenceType)
                .Include(x => x.ParentReferences).ThenInclude(x=>x.ReferenceType)
                .Include(x=>x.businessGlosItemComments)
                .SingleOrDefaultAsync(m => m.Id == id);

      if (BusinessGlosItem == null)
      {
           return NotFound();
      }
      return Page();
 }

非常感谢！

Answer 1

您忘记为ThenInclude和ChildBGItem的{{1}}和ParentBGItem都提到ChildReferences。因此，您的查询应如下所示：

ParentReferences

现在应该可以了。

包括关联表中的数据

1 个答案: