微风投影：选择非标量导航属性时出错 [英] breeze projection : error selecting non scalar navigation properties

问题描述

大家好。下面您可以看到在我的数据库中进行的EF Power Tools逆向工程的部分结果。

  public partial class Articoli { 
 public decimal Id_Articolo {get;组; } 
 public string Codice {get;组; } 
 public virtual ICollection< Udc_Dettaglio> FK_Udc_Dettaglio_Articoli {get;组; } 
} 
 
 public partial class Udc_Dettaglio {
 public decimal Id_Udc {get;组; } 
 public decimal Id_Articolo {get;组; } 
 public virtual Articoli FK_Udc_Dettaglio_Articoli {get;组; } 
} 
 
 public Udc_DettaglioMap（）{
 //主键
 this.HasKey（t => new {t.Id_Udc，t.Id_Articolo}） ; 
 
 //关系
 this.HasRequired（t => t.FK_Udc_Dettaglio_Articoli）
 .WithMany（t => t.FK_Udc_Dettaglio_Articoli）
 .HasForeignKey（d = d.Id_Articolo）; 
} 
  

如果通过使用微风，我尝试执行此查询

  breeze.EntityQuery.from（Articoli）。expand（FK_Udc_Dettaglio_Articoli）
  pre> 
 
 
或这一个
  breeze.EntityQuery.from（ Articoli）选择（Codice，FK_Udc_Dettaglio_Articoli）
  
一切正常，但如果我尝试这个
  breeze.EntityQuery.from（Articoli）。select（Codice，FK_Udc_Dettaglio_Articoli.Id_Udc）
  
它抛出一个exeption：
 
 
 
无法找到属性 Id_Udc'类型'System.Collections.Generic.ICollection`1 [AWM.Models.Udc_Dettaglio]'。
 
 
 
我在EF模型定义中缺少某些东西？不是因为扩展实用程序正在工作... 
解决方案
我相信您正在尝试构建EF不支持的查询（和OData查询语法d也不支持。
 
 
 
您的 FK_Udc_Dettaglio_Articoli 是 Articoli的集合导航属性。通过尝试在该集合中的每个元素的 Id_Udc 属性后，您实际上正在尝试在投影中创建投影而EF不支持我所知道的。
 
 
 
要验证，尝试在服务器端构建一个执行所需操作的LINQ查询。像
  dbContext.Articoli.Select（
a => new {a.Codice，a.FK_Udc_Dettaglio_Articoli.Select （f => new {f.Id_Udc}））; 
  
您将很快发现该查询无法编译。您会收到一条消息，如匿名类型投影初始化程序应该是简单的名称或成员访问扩展。
 
Ho to everybody. Below you can see the partial result of the EF Power Tools reverse engineering made on the database of mine.
public partial class Articoli {        
    public decimal Id_Articolo { get; set; }
    public string Codice { get; set; }
    public virtual ICollection<Udc_Dettaglio> FK_Udc_Dettaglio_Articoli { get; set; }
}

public partial class Udc_Dettaglio {
    public decimal Id_Udc { get; set; }
    public decimal Id_Articolo { get; set; }
    public virtual Articoli FK_Udc_Dettaglio_Articoli { get; set; }
}

public Udc_DettaglioMap() {
    // Primary Key
    this.HasKey(t => new { t.Id_Udc, t.Id_Articolo });

    // Relationships
    this.HasRequired(t => t.FK_Udc_Dettaglio_Articoli)
        .WithMany(t => t.FK_Udc_Dettaglio_Articoli)
        .HasForeignKey(d => d.Id_Articolo);        
}
If, by using breeze, i try to perform this query
breeze.EntityQuery.from("Articoli").expand("FK_Udc_Dettaglio_Articoli")
or this one 
breeze.EntityQuery.from("Articoli").select("Codice,FK_Udc_Dettaglio_Articoli")
everything works fine, but if i try with this 
breeze.EntityQuery.from("Articoli").select("Codice,FK_Udc_Dettaglio_Articoli.Id_Udc")
it throw an exeption : 

Unable to locate property 'Id_Udc' on type 'System.Collections.Generic.ICollection`1[AWM.Models.Udc_Dettaglio]'."

Am I missing something in EF model definition ? i guess not because expand utility is working ...
解决方案
I believe you are trying to build a query that EF doesn't support (and that OData query syntax doesn't support either).

Your FK_Udc_Dettaglio_Articoli is a collection navigation property of Articoli. By trying to go after just the Id_Udc property of each element in that collection, you are actually trying to create a projection within a projection ... and EF doesn't support that as far as I know.

To verify, try to construct a LINQ query on the server side that does what you want. Something like
dbContext.Articoli.Select(
    a => new {a.Codice, a.FK_Udc_Dettaglio_Articoli.Select(f => new {f.Id_Udc}));
You'll quickly discover that that query does not compile. You get a message something like "anonymous type projection initializer should be simple name or member access expansion".

                        
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