Question

我需要来自2个不同数据库的数据。我试过以下

var User = (from U in _db.TblUsers
                        where U.IsAdmin == false
                        select U).ToList();

var AspNewsUser = (from A in _dbAspNet.aspnet_Users                        
                   select A).ToList();


var result = (from U in User
              join A in AspNewsUser
              on U.UserID equals A.UserId
              select U);

但是我收到以下错误消息

join子句中某个表达式的类型不正确。调用“加入”时类型推断失败。

Answer 1

正如您在table schema of aspnet_Users中看到的那样，Userid是uniqueidentifier（映射到实体框架中的GUID）。我敢打赌TblUsers.UserID有不同的类型（如int）。

Answer 2

使用投影，使它们成为相同的匿名类型。

    var Users = (from U in _db.TblUsers
                    where U.IsAdmin == false
                    select new { UserID = U.UserID }).ToList();

    var AspNewsUsers = (from A in _dbAspNet.aspnet_Users                        
                    select new { UserID = A.UserID }).ToList();


    var result = (from i in Users join o in AspNewUsers on i.UserID equals o.UserID).ToList();

由于类型不匹配，LINQ加入失败

2 个答案: