错误：无法隐式转换为System.linq.iqueryable< System.Linq.IGrouping< string，AnonymousType＃1>> to system.Collection.List<>，并且显式转换存在..你错过了演员吗？ [英] Error: Cannot Implicitly Convert to To System.linq.iqueryable<System.Linq.IGrouping<string,AnonymousType#1>> to system.Collection.List<>, and explicit conversion exist..are you missing a cast ?

问题描述

我对asp.net不是很熟悉。简要解释为什么em遇到这个错误。



这是我的代码

  public  List< Department> getDeptNames（）{
 使用（
 RailwayElectricBillingDBEntities context =  new  RailwayElectricBillingDBEntities（）） 
 {
  var  obj = context.Departments.ToList（）; 
列表<部门> dic =（ from  p  in  context.Departments 
 选择  new  {p.DepartmentId，p.DepartmentName}）。GroupBy（o = >  o.DepartmentName）; 
  return  obj; 
 
}} 

解决方案

假设您的部门课程是什么

  public   class  department 
 { 
  public   int  DepartmentId { get ;  set ; } 
  public   string  DepartmentName { get ;  set ; } 
} 

然后你需要像这样编写你的查询... < br $> b $ b

  public 列表< Department> getDeptNames（）
 {
 使用（RailwayElectricBillingDBEntities context =  new  RailwayElectricBillingDBEntities（）） 
 {
 List< Department> dic =（ from  p  in  context.Departments 
 选择  new 部门
 {
 DepartmentId = p.DepartmentId，
 DepartmentName = p.DepartmentName 
 } 
）.ToList（）; 
  return  obj; 
} 
} 

（来自上下文中的p.Departments 
 select new {p。 DepartmentId，p.DepartmentName}）。GroupBy（o => o.DepartmentName）; 

您选择匿名类型，因此无法将其强制转换为列表< department>< / department>





尝试：

（来自 p   context.Departments 
  select  p）。 GroupBy（o = >  o.DepartmentName）。ToList（）; 

试试这个< br $> b $ b

列表< department> dic =（List< department>）（ from  p  in  context.Departments 
 选择  new  {p.DepartmentId，p.DepartmentName}）。GroupBy（o = >  o.DepartmentName）; < /   department  >  < /   department  >  

hy i am not very much familiar to asp.net . Explain briefly why em encountering this error.

here is my code

public List<Department> getDeptNames(){
using (
RailwayElectricBillingDBEntities context = new RailwayElectricBillingDBEntities())
{
var obj = context.Departments.ToList();
List<Department> dic = (from p in context.Departments
select new { p.DepartmentId, p.DepartmentName }).GroupBy( o=> o.DepartmentName);
return obj;

}}

解决方案

suppose your Department class is something

public class department
   {
       public int DepartmentId { get; set; }
       public string DepartmentName  { get; set; }
   }

then you need to write your query like this...

public List<Department> getDeptNames()
    {
        using (RailwayElectricBillingDBEntities context = new RailwayElectricBillingDBEntities())
        {
            List<Department> dic = (from p in context.Departments
                                    select new Department
                                        {
                                            DepartmentId = p.DepartmentId,
                                            DepartmentName = p.DepartmentName
                                        }
                                    ).ToList();
            return obj;
        }
    }

(from p in context.Departments
select new { p.DepartmentId, p.DepartmentName }).GroupBy( o=> o.DepartmentName);

You are selecting an Anonymous type, hence will not be able to cast it to List<department></department>


Try:

(from p in context.Departments
select p).GroupBy( o=> o.DepartmentName).ToList();

Try this

List<department> dic =(List<department>) (from p in context.Departments
select new { p.DepartmentId, p.DepartmentName }).GroupBy( o=> o.DepartmentName);</department></department>

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