实体或复合类型“FPSDB_newModel.Form_Attachment”不能在LINQ to Entities查询中构建 [英] The entity or complex type 'FPSDB_newModel.Form_Attachment' cannot be constructed in a LINQ to Entities query

问题描述

我正在使用Entity Framework DB的第一种方法。当我想从数据库中提取数据时，我使用方法 GetForm_AttachmentByAppID 。当我从我的代码调用这个方法时，我得到以下运行时错误：

  EntityFramework.SqlServer.dll中发生了类型System.NotSupportedException的异常，但在用户代码中未处理
 
附加信息：不能在LINQ to Entities查询中构造实体或复合类型FPSDB_newModel.Form_Attachment。 
  

  public partial class Form_Attachment 
 {
 public int Form_AttachmentID {get;组; } 
 public Nullable< int> AttachmentCategoryID {get;组; } 
 public int ApplicationID {get;组; } 
 public string EmployeeID {get;组; } 
 public string DocumentName {get;组; } 
 public string DocumentSize {get;组; } 
 public Nullable< byte> RoleID {get;组; } 
 public string描述{get;组; } 
 public Nullable< bool> SelectionForExtRev {get;组; } 
 
 public virtual Application Application {get;组; } 
 public virtual AttachmentCategory AttachmentCategory {get;组; } 
 public virtual Employee Employee {get;组; } 
 public virtual Role Role {get;组; } 
} 
  

上述文件是自动生成的，代码存在于 FPSModel.cs ，而下面是我的代码来拉取数据

  public List< Form_Attachment> GetForm_AttachmentByAppID（int applicationID）
 {
 var context = new FPSDB_newEntities（）; 
 var data =（from f in context.Form_Attachment 
其中
（
 f.ApplicationID == applicationID 
）
选择新Form_Attachment 
 {
 Form_AttachmentID = f.Form_AttachmentID，
 AttachmentCategoryID = f.AttachmentCategoryID，
 EmployeeID = f.EmployeeID，
 ApplicationID = f.ApplicationID，
 DocumentName = f.DocumentName ，
 DocumentSize = f.DocumentSize，
 RoleID = f.RoleID，
描述= f.Description，
 SelectionForExtRev = f.SelectionForExtRev 
}）ToList（） ; 
返回数据; 
} 
  

这里也是我的表格的数据库定义 Form_Attachments

  CREATE TABLE [dbo]。[Form_Attachment]（
 [Form_AttachmentID] [int] IDENTITY ）NOT NULL，
 [AttachmentCategoryID] [int] NULL，
 [ApplicationID] [int] NOT NULL，
 [EmployeeID] [varchar]（10）NOT NULL，
 [文件名] [nvarchar]（500）NULL，
 [DocumentSize] [nvarchar]（50）NULL，
 [RoleID] [tinyint] NULL，
 [描述] [ntext] b $ b [SelectionForExtRev] [bit] NULL，
 CONSTRAINT [PK_Form_AttachmentID] PRIMARY KEY CLUSTERED 
（
 [Form_AttachmentID] ASC 
）WITH（PAD_INDEX = OFF，STATISTICS_NORECOMPUTE = OFF， $ PR $ ON ON ON $ $ ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON $ $ 
 $ b 
我已经阅读了这个 Proj ection不应该被映射到实体 
所以如果我创建一个类 Form_Attachments1 ，就像自动生成的 Form_Attachments 一样，它将成为一个数据转移对象DTO是一种正确的方法。
解决方案
您可以尝试以下方式：
  public List< Form_Attachment> GetForm_AttachmentByAppID（int applicationID）
 {
 var context = new FPSDB_newEntities（）; 
 var data =（from f in context.Form_Attachment 
 where 
（
 f.ApplicationID == applicationID 
）
 select f）.ToList（） ; 
返回数据; 
} 
  
或此：
  data = context.Form_Attachment.Where（p => p.ApplicationID == applicationID）.ToList（）; 
  
我现在无法测试，但这应该可以工作。你不需要映射，因为'f'意味着你的'Form_Attachment'实体类已经。如果您使用像Form_AttachmentDto这样的DTO类，那么您需要像这样映射：
  public List< Form_AttachmentDto> ; GetForm_AttachmentByAppID（int applicationID）
 {
 var context = new FPSDB_newEntities（）; 
 var data =（from f in context.Form_Attachment 
 where 
（
 f.ApplicationID == applicationID 
）
 select f）.Select（p => new Form_AttachmentDto（）
 {
 // ... 
 //这里映射代码
 // .. 
} 
） .ToList（）; 
返回数据; 
} 
  
 
I am using Entity Framework DB first approach. When I want to pull the data from DB I use the method GetForm_AttachmentByAppID.I get the following run time error when I call this method  from my code:

An exception of type 'System.NotSupportedException' occurred in     EntityFramework.SqlServer.dll but was not handled in user code

Additional information: The entity or complex type 'FPSDB_newModel.Form_Attachment' cannot be constructed in a LINQ to Entities query.

public partial class Form_Attachment
{
public int Form_AttachmentID { get; set; }
public Nullable<int> AttachmentCategoryID { get; set; }
public int ApplicationID { get; set; }
public string EmployeeID { get; set; }
public string DocumentName { get; set; }
public string DocumentSize { get; set; }
public Nullable<byte> RoleID { get; set; }
public string Description { get; set; }
public Nullable<bool> SelectionForExtRev { get; set; }

public virtual Application Application { get; set; }
public virtual AttachmentCategory AttachmentCategory { get; set; }
public virtual Employee Employee { get; set; }
public virtual Role Role { get; set; }
}    
The above file is auto-generated and the code is present in FPSModel.cs while below is my code to pull data 
public List<Form_Attachment> GetForm_AttachmentByAppID(int applicationID)
{
    var context = new FPSDB_newEntities();
    var data = (from f in context.Form_Attachment
                where
                (
                f.ApplicationID== applicationID
                )
                select new Form_Attachment
                {
                    Form_AttachmentID = f.Form_AttachmentID,
                    AttachmentCategoryID = f.AttachmentCategoryID,
                    EmployeeID = f.EmployeeID,
                    ApplicationID = f.ApplicationID,
                    DocumentName = f.DocumentName,
                    DocumentSize = f.DocumentSize,
                    RoleID = f.RoleID,
                    Description = f.Description,
                    SelectionForExtRev = f.SelectionForExtRev
                }).ToList();
    return data;
}
Also here is the DB definition of my table Form_Attachments
CREATE TABLE [dbo].[Form_Attachment](
[Form_AttachmentID] [int] IDENTITY(1,1) NOT NULL,
[AttachmentCategoryID] [int] NULL,
[ApplicationID] [int] NOT NULL,
[EmployeeID] [varchar](10) NOT NULL,
[DocumentName] [nvarchar](500) NULL,
[DocumentSize] [nvarchar](50) NULL,
[RoleID] [tinyint] NULL,
[Description] [ntext] NULL,
[SelectionForExtRev] [bit] NULL,
 CONSTRAINT [PK_Form_AttachmentID] PRIMARY KEY CLUSTERED 
(
[Form_AttachmentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,     ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
I have read this The Projection should not be on to a mapped entity
So if i make a class Form_Attachments1 just like auto-generated  Form_Attachments so will it be a Data Transfer object DTO and is it a right approach.
解决方案
You can try this:
public List<Form_Attachment> GetForm_AttachmentByAppID(int applicationID)
{
    var context = new FPSDB_newEntities();
    var data = (from f in context.Form_Attachment
                where
                (
                f.ApplicationID== applicationID
                )
                select f).ToList();
    return data;
}
or this:
data = context.Form_Attachment.Where(p => p.ApplicationID == applicationID).ToList();
I can't test it now, but this should work. You don't need to map because 'f' means your 'Form_Attachment' entity class already. If you were using a DTO class like 'Form_AttachmentDto', then you would need to map it like this:
public List<Form_AttachmentDto> GetForm_AttachmentByAppID(int applicationID)
    {
        var context = new FPSDB_newEntities();
        var data = (from f in context.Form_Attachment
                    where
                    (
                    f.ApplicationID== applicationID
                    )
                    select f).Select(p=>new Form_AttachmentDto() 
                        { 
                        //...
                        // here comes the mapping code
                        //..
                        }
                    ).ToList();
        return data;
    }


                        
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