【发布时间】：2021-02-09 09:03:57
【问题描述】：
开发环境
- ASP.NET Core 3.1
- Microsoft.EntityFrameworkCore 3.1.9
- Microsoft.AspNetCore.OData 7.5.1
型号
public class Computer
{
public int Id { get; set; }
public string Name { get; set; }
public ICollection<Disk> Disks { get; set; }
}
public class Disk
{
public int Id { get; set; }
public string Letter { get; set; }
public float Capacity { get; set; }
public int? ComputerId { get; set; }
public virtual Computer Computer { get; set; }
}
Dtos
public class ComputerDto
{
public int Id { get; set; }
public string Name { get; set; }
public ICollection<DiskDto> Disks { get; set; }
}
public class DiskDto
{
public string Letter { get; set; }
public float Capacity { get; set; }
}
EF 核心上下文
public class ComputerContext : DbContext
{
public DbSet<Computer> Computers { get; set; }
public DbSet<Disk> Disks { get; set;}
public ComputerContext(DbContextOptions<ComputerContext> options)
: base(options)
{
}
}
OData EDM 模型
private static IEdmModel GetEdmModel()
{
var builder = new ODataConventionModelBuilder();
builder.EntitySet<Computer>("Computers");
builder.EntitySet<Disk>("Disks");
builder.ComplexType<ComputerDto>();
builder.ComplexType<DiskDto>();
return builder.GetEdmModel();
}
ASP.NET Core 控制器
[Route("api/[controller]")]
[ApiController]
public class ComputersController : ControllerBase
{
private readonly ComputerContext context;
public ComputersController(ComputerContext context)
{
this.context = context;
}
[HttpGet]
[EnableQuery]
public IQueryable<ComputerDto> GetComputers()
{
return this.context.Computers.Select(c => new ComputerDto
{
Id = c.Id,
Name = c.Name,
Disks = c.Disks.Select(d => new DiskDto
{
Letter = d.Letter,
Capacity = d.Capacity
}).ToList()
});
}
}
此查询有效，但磁盘已展开，因为我正在手动创建列表。
https://localhost:46324/api/computers?$filter=startswith(name,'t')
和输出
{
"@odata.context": "https://localhost:46324/api/$metadata#Collection(ODataPlayground.Dtos.ComputerDto)",
"value": [
{
"Id": 14,
"Name": "TestComputer1",
"Disks": [
{
"Letter": "C",
"Capacity": 234.40
},
{
"Letter": "D",
"Capacity": 1845.30
}
]
},
{
"Id": 15,
"Name": "TestComputer2",
"Disks": [
{
"Letter": "C",
"Capacity": 75.50
},
{
"Letter": "D",
"Capacity": 499.87
}
]
}
]
}
如果我尝试使用以下查询扩展“磁盘”，则会收到错误消息：
https://localhost:46324/api/computers?$filter=startswith(name,'t')&$expand=disks
错误
{
"error": {
"code": "",
"message": "The query specified in the URI is not valid. Property 'disks' on type 'ODataPlayground.Dtos.ComputerDto' is not a navigation property or complex property. Only navigation properties can be expanded.",
"details": [],
"innererror": {
"message": "Property 'disks' on type 'ODataPlayground.Dtos.ComputerDto' is not a navigation property or complex property. Only navigation properties can be expanded.",
"type": "Microsoft.OData.ODataException",
"stacktrace": "...really long stack trace removed for compactness..."
}
}
}
问题
- 我似乎能够将顶级类作为 dto 返回，只公开客户端可能需要的属性，但是否也可以公开并返回 dto 作为导航属性？
非dto输出
{
"@odata.context": "https://localhost:46324/api/$metadata#Collection(ODataPlayground.Dtos.ComputerDto)",
"value": [
{
"Id": 14,
"Name": "TestComputer1",
"Disks": [
{
"Id": 16,
"ComputerId": 14,
"Letter": "C",
"Capacity": 234.40
},
{
"Id": 17,
"ComputerId": 14,
"Letter": "D",
"Capacity": 1845.30
}
]
}
]
}
所需的输出（使用上面的 $filter 和 $expand 查询）
{
"@odata.context": "https://localhost:46324/api/$metadata#Collection(ODataPlayground.Dtos.ComputerDto)",
"value": [
{
"Id": 14,
"Name": "TestComputer1",
"Disks": [
{
"Letter": "C",
"Capacity": 234.40
},
{
"Letter": "D",
"Capacity": 1845.30
}
]
}
]
}
更新 #1
如果我将 Automapper 添加到组合中并尝试使用带有以下代码的 ProjectTo 方法：
//// Inject context and mapper
public ComputersController(ComputerContext context, IMapper mapper)
{
this.context = context;
this.mapper = mapper;
}
[HttpGet]
[EnableQuery]
public IQueryable<ComputerDto> GetComputers()
{
return this.context.Computers.ProjectTo<ComputerDto>(mapper.ConfigurationProvider);
}
我得到一个不同的错误：
InvalidOperationException: When called from 'VisitLambda', rewriting a node of type
'System.Linq.Expressions.ParameterExpression' must return a non - null value of the same type.
Alternatively, override 'VisitLambda' and change it to not visit children of this type.
【问题讨论】：
-
disks != Disks，可能是错误？ -
很遗憾，
$expand=Disks不会产生不同的结果。 -
OData 无法识别 ComputerDto > Disks 作为导航属性，因为这是一个复杂类型，您需要使用 builder.ComplexType
() 告诉 OData Disks 是一个关系（可扩展）属性.HasMany(c => c.Disks); // 这只有在 DiskDto 有 Id 时才有效 -
@RodrigoGRodrigues 是否无法将 OData 查询应用到 Computer，然后将结果映射到 ComputerDto？
-
您可能需要考虑为此使用存储过程。
标签： c# asp.net-core entity-framework-core odata