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[英]C# Entity Framework 6 with ASP.Net web API returning empty array in JSON response
[英]ASP.NET Web API returns empty collection in json response
好的,我对ASP.NET Web API有问题。 我按照本教程讲解如何创建它。 我为自己的目的对本教程进行了修改。
我有一个修补程序类,其中包含下载URL的集合。 API返回的所有信息都很好,只有DownloadURLs的集合返回为null。 但是,当我逐步调试代码时,它正确地返回了集合。 我做错了什么。 我找不到我的错误。 这是模型:
public class Patch
{
[Key]
[Required]
[JsonProperty("PatchVersion")]
public string PatchVersion { get; set; }
[Required]
[JsonProperty("Length")]
public long Length { get; set; }
[JsonProperty("VersionToUpdateFrom")]
public string VersionToUpdateFrom { get; set; }
[JsonProperty("DownloadUris")]
public ICollection<DownloadUri> DownloadUris { get; set; }
}
public class DownloadUri
{
[Key]
[Required]
[JsonProperty("AbsolutePath")]
public string AbsolutePath { get; set; }
[Required]
[JsonProperty("IndirectDownload")]
public bool IndirectDownload { get; set; }
}
这是我的DataContext类:
public class PatchesContext : DbContext
{
public PatchesContext()
: base("name=PatchesContext")
{
}
public DbSet<Patch> Patches { get; set; }
public DbSet<DownloadUri> DownloadUris { get; set; }
}
这是ContextInitializer
public class PatchesContextInitializer : DropCreateDatabaseIfModelChanges<PatchesContext>
{
protected override void Seed(PatchesContext context)
{
var downloadUri = new List<DownloadUri>
{
new DownloadUri
{
AbsolutePath = "http://downloadUri1.test", IndirectDownload = false
},
new DownloadUri
{
AbsolutePath = "http://downloadUri2.test", IndirectDownload = false
}
};
var patches = new List<Patch>
{
new Patch
{
Length = 100000, PatchVersion = "1.0.0.0", VersionToUpdateFrom = string.Empty, DownloadUris = downloadUri
},
new Patch
{
DownloadUris = null, Length = 10000, PatchVersion = "1.1.0.0", VersionToUpdateFrom = "1.0.0.0"
}
};
patches.ForEach(p => context.Patches.Add(p));
context.SaveChanges();
}
}
最后是我的控制器类。 我遗漏了Post,Put和Delete方法,因为我还没有测试它们(如果get不能正常工作,那毫无意义):
public class AdminController : ApiController
{
private PatchesContext db = new PatchesContext();
// GET api/Admin
public IEnumerable<Patch> GetPatches()
{
return db.Patches.AsEnumerable();
}
// GET api/Admin/5
public Patch GetPatch(string version)
{
Patch patch = db.Patches.Find(version);
if (patch == null)
{
throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotFound));
}
return patch;
}
}
希望大家能帮助我,谢谢。
/ edit:标题看起来像这样:
Status Code: 200 OK
Cache-Control: no-cache
Content-Length: 291
Content-Type: application/json; charset=utf-8
Date: Fri, 25 Oct 2013 17:25:48 GMT
Expires: -1
Pragma: no-cache
Server: Microsoft-IIS/8.0
X-SourceFiles: =?UTF-8?B?RTpcVXNlcnNcUm9iZXJ0XERvY3VtZW50c1xWaXN1YWwgU3R1ZGlvIDIwMTJcUHJvamVjdHNcTjQ0V2Vic2l0ZVxONDRXZWJzaXRlXGFwaVxhZG 1pbg==?=
响应主体如下所示:
[
{
"$id": "1",
"PatchVersion": "1.0.0.0",
"Length": 100000,
"VersionToUpdateFrom": "",
"DownloadUris": null
},
{
"$id": "2",
"PatchVersion": "1.1.0.0",
"Length": 10000,
"VersionToUpdateFrom": "1.0.0.0",
"DownloadUris": null
}
]
您既没有显式加载Patch.DownloadUris属性,也不是虚拟属性,因此也不会延迟加载它。
通过以下行中的DownloadUris的Include显式加载它:
Patch patch = db.Patches.Find(version);
到(未经测试)
Patch patch = db.Patches.Find(version).Include("DownloadUris");
或将该属性设为虚拟,并确保在上下文中启用了延迟加载。
编辑说明:在代码示例中为Seed方法指定的情况下,只有补丁(1.0.0.0)才具有DownloadUris的值,因为在补丁(1.1.0.0)中,您将该属性设置为null
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