.net - 当我得到一件商品时 $Expand 不起作用

Question

我为移动应用程序准备了 Odata API，但 $Expand 存在问题。当我使用这个查询时，一切正常。

查询: .../odata/forms?$expand=FormFields($expand=FormFieldRadios)&$filter=FormId eq 1

但是当我使用这个查询时:

.../odata/forms(1)?$expand=FormFields($expand=FormFieldRadios)

展开不起作用，项目集合为空。

我的 json 结果 Items coolection One item

My nugets

配置服务:

services.AddOData();
services.AddODataQueryFilter();
services.AddMvc(options =>
    {
        // https://blogs.msdn.microsoft.com/webdev/2018/08/27/asp-net-core-2-2-0-preview1-endpoint-routing/
        options.EnableEndpointRouting = false;
    }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

配置

app.UseMvc(routeBuilder =>
{
    routeBuilder.Select().Expand().Filter().Count().OrderBy().MaxTop(250).Expand(QueryOptionSetting.Allowed);
    routeBuilder.MapODataServiceRoute("odata", "odata", GetEdmModel(app.ApplicationServices));
});

模型构建器

 builder.EntitySet<Form>("Forms").EntityType.Filter().Count().Expand(OdataDefaults.MaxExpansionDepth).OrderBy().Page().Select();

表单实体

 public class Form
 {
     [Key, Required]
     public int FormId { get; set; }

     [Required]
     public int Order { get; set; }

     [Required]
     public bool Active { get; set; }

     [Required, MaxLength(255)]
     public string Name { get; set; }

     public int IsDeleted { get; set; }

     [MaxLength(255)]
     public string SuccessMessage { get; set; }

     public ICollection<FormField> FormFields { get; set; } = new List<FormField>();
 }

Odata Controller

public class FormsController : ODataController
{
    private VillageContext _db;

    public FormsController(VillageContext context)
    {
        _db = context;
    }

    [EnableQuery(AllowedFunctions = OdataDefaults.AllowedFunctions, MaxExpansionDepth = OdataDefaults.MaxExpansionDepth, PageSize = OdataDefaults.PageSize)]
    public IActionResult Get()
    {
        return Ok(_db.Forms);
    }


    [EnableQuery(AllowedFunctions = OdataDefaults.AllowedFunctions, MaxExpansionDepth = OdataDefaults.MaxExpansionDepth, PageSize = OdataDefaults.PageSize)]
    public IActionResult Get([FromODataUri] int key)
    {
        return Ok(_db.Forms.Find(key));
    }
}

Answer 1

EntityFramework 的 Find方法不返回 IQueryable<TEntity>而是TEntity本身。因此，OData 无法再对其进行扩展是合乎逻辑的，因为不再需要“修改”表达式树。 将您的功能更改为:

[EnableQuery(AllowedFunctions = OdataDefaults.AllowedFunctions, MaxExpansionDepth = OdataDefaults.MaxExpansionDepth, PageSize = OdataDefaults.PageSize)]
public IActionResult Get([FromODataUri] int key)
{
    return Ok(SingleResult.Create(_db.Forms.Where(form => form.FormId == key)));
}