出现无法隐式转换类型泛型列表的错误

Posted 2023-04-13

【中文标题】出现无法隐式转换类型泛型列表的错误

【英文标题】：getting error of can not implicit convert type generic list

【发布时间】：2021-03-15 07:05:17

【问题描述】：

我有课。

 public partial class RecentlyViewedReport
  
    public int Id  get; set; 
    public string Email  get; set; 
    public int ReportId  get; set; 
    public DateTime DateTime  get; set; 

    public virtual Report Report  get; set; 

我有一个从 sql 表中检索数据的方法。

        public List<RecentlyViewedReport> GetRecentlyViewedReports(string userEmailId)
    
        var result = (from pd in _context.RecentlyViewedReports
                 join od in _context.Reports on pd.ReportId equals od.Id
                 orderby pd.DateTime descending
                 select 
                 new
                 
                     Id= pd.Id,
                     Email= pd.Email,
                     ReportId=pd.ReportId,
                     DateTime=pd.DateTime,
                     Report= od as Report //This lines giving me error
                 ).ToList();

        return result;
    

获取Report数据的正确方法是什么

【问题讨论】：

od 是一个列表。如果您只期待一份报告，那么您可以尝试“od.First() as Report”

我得到了解决方案。

select new RecentViewedReport() Id = pd.Id, Email = pd.Email, ReportId = pd.ReportId, DateTime = pd.DateTime, Report = od ).ToList();跨度>

【参考方案1】：

试试这个...

 var result = _context.RecentlyViewedReports.Include(c => c.Report)
                       .OrderByDescending(c => c.DateTime)
                       .Select(c => new
                         
                           Id = c.Id,
                           Email = c.Email,
                           ReportId = c.ReportId,
                           DateTime = c.DateTime,
                           Report = c.Report
                         ).ToList();

【讨论】：

未来的读者会真正受益于解释为什么您的代码解决了问题以及 OP 首先在他们的方法中做错了什么。