LINQ to Entities无法识别方法'System.Collections.Generic.Dictionary`2 [System.Int32，System.String] ToDictionary [英] LINQ to Entities does not recognize the method 'System.Collections.Generic.Dictionary`2[System.Int32,System.String] ToDictionary

问题描述

我正在尝试从数据库中检索存储在Employee表中的EmployeeDTO列表.每个员工可以拥有一个或多个专业.专业存储在OrganizationSpecialtyType中. Employee和OrganizationSpecialtyType通过EmployeeSpecialty表与多对多"相关.

I am trying to retrieve list of EmployeeDTO from DB which are stored in Employee table. Every employee can have one or more specialty. Specialty are stored in OrganizationSpecialtyType. Employee and OrganizationSpecialtyType are related with "many-to-many" via EmployeeSpecialty table.

我正在使用以下查询，但出现了类似于标题中的异常:

I'm using the following query for that, and got an exception like in title:

var q = _context.Employee.Where(p => employeeEMIIDs.Contains(p.EmployeeID))
            .Select(p => new EmployeeDTO
                                    {
                                        EmployeeID = p.EmployeeID,
                                        GenderTypeID = p.GenderTypeID,
                                        FirstName = p.FirstName,
                                        LastName = p.LastName,
                                        Name = p.Name,
                                        MiddleName = p.MiddleName,
                                        DOB = p.DOB,
                                        Suffix = p.Suffix,
                                        Title = p.Title,
                                        Specialty = p.EmployeeSpecialty
                                                            .ToDictionary(d => d.OrganizationSpecialtyType.SpecialtyTypeID, d => d.OrganizationSpecialtyType.Name)
                                    }
                        );

在EmployeeDTO类中，属性Specialty键入public Dictionary<int, string>.

如果执行此查询，则一切正常:

If I execute this query, everything works normally:

var spec = _context.Employee.Where(p => p.EmployeeID == -9070).FirstOrDefault()
    .EmployeeSpecialty.ToDictionary(d =>
         d.OrganizationSpecialtyType.SpecialtyTypeID,
         d => d.OrganizationSpecialtyType.Name);

如何解决我的第一个查询以获得具有特殊性的EmployeeDTO?

How I can solve my first query to obtain EmployeeDTO with specialties?

谢谢.

推荐答案

您可以先选择匿名类型，然后再设置字典.

You can select to anonymous type first, then set the dictionary later.

var q = _context.Employee.Where(p => employeeEMIIDs.Contains(p.EmployeeID))
    .Select(p => new
    {
        Employee = new EmployeeDTO
        {
             EmployeeID = p.EmployeeID,
             GenderTypeID = p.GenderTypeID,
             FirstName = p.FirstName,
             LastName = p.LastName,
             Name = p.Name,
             MiddleName = p.MiddleName,
             DOB = p.DOB,
             Suffix = p.Suffix,
             Title = p.Title
         },
         Specialty = p.EmployeeSpecialty
             .Select(d => new 
             {
                 d.OrganizationSpecialtyType.SpecialtyTypeID,
                 d.OrganizationSpecialtyType.Name
             })
    })                    
    .AsEnumerable()
    .Select(a => 
    {
        a.Employee.Specialty = a.Specialty
            .ToDictionary(d => d.SpecialtyTypeID, d => d.Name);
        return a.Employee;
    });

这篇关于LINQ to Entities无法识别方法'System.Collections.Generic.Dictionary`2 [System.Int32，System.String] ToDictionary的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！