Question

我正在尝试加入两列，但其中一列是Varchar，另一列是NVarchar

我的LINQ代码：

private BrattleHubEntities officeInfo = new BrattleHubEntities();
private BrattlecubesEntities empInfo = new BrattlecubesEntities();

var employeeOfficeInfo = from t1 in officeInfo.DimOffices
                                     join t2 in empInfo on t1.OfficeCode equals t2.EmployeeOffice
                                     select new { t1.OfficeCode, t1.MainPhone, t1.MainFax }

这会显示错误消息：

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。

从研究中我了解到这是因为empInfo.EmployeeOffice是NVarchar(30)而officeInfo.OfficeCode是Varchar(20)

如何投射这些字符串以执行加入？

提前谢谢

更新即使使用以下代码，我也收到同样的错误

var employeeOfficeInfo = from t1 in officeInfo.DimOffices
                                     join t2 in empInfo on 1 equals 1
                                     select new { t1.OfficeCode, t1.MainPhone, t1.MainFax }

Answer 1

您可以使用嵌套linq查询返回的anon对象在子查询中显式转换两种类型的值，然后连接两个子查询的结果以返回所需的对象。问题在技术上不是一个SQL服务器，它是一个.NET服务器。 LINQ不知道如何将映射对象的这两种数据类型连接在一起。所以你需要明确地告诉链接这两种类型是如何相关的。或者，您可以使用tsql执行此查询并将varchar转换为nvarchar。 JOIN t2 ON (CONVERT(NVARCHAR(30), t1.OfficeCode, 0) = t2.EmployeeOffice)

Answer 2

我解决了这个问题，对不起，我排除了罪魁祸首。

原始代码（完整）

private BrattleHubEntities officeInfo = new BrattleHubEntities();
private BrattlecubesEntities empInfo = new BrattlecubesEntities();

        // GET: DimOffices
        public ActionResult Index()
        {

            string currentUser = System.Security.Principal.WindowsIdentity.GetCurrent().Name;
            string currentUserLogin = currentUser.Substring(10);
            var employee = from e in empInfo.DimEmployees//Method 1 to pull current user
                           select e;
            employee = employee.Where(e => e.UserLogin.Contains(currentUser) && e.EmployeeOffice.Contains("BOS"));

            var employeeOfficeInfo = from t1 in officeInfo.DimOffices
                                     join t2 in empInfo on t1.OfficeCode equals t2.EmployeeOffice
                                     select new { t1.OfficeCode, t1.MainPhone, t1.MainFax };

            return View(employeeOfficeInfo);
        }

运行代码

private BrattleHubEntities officeInfo = new BrattleHubEntities();
private BrattlecubesEntities empInfo = new BrattlecubesEntities();

        // GET: DimOffices
        public ActionResult Index()
        {

            string currentUser = System.Security.Principal.WindowsIdentity.GetCurrent().Name;
            string currentUserLogin = currentUser.Substring(10);
            var employee = from e in empInfo.DimEmployees//Method 1 to pull current user
                           select e;
            employee = employee.Where(e => e.UserLogin.Contains(currentUser));

            var employeeOfficeInfo = from t1 in officeInfo.DimOffices
                                     join t2 in employee on t1.OfficeCode equals t2.EmployeeOffice
                                     select new { t1.OfficeCode, t1.MainPhone, t1.MainFax };

            return View(employeeOfficeInfo);
        }

问题在于我已经在EmpInfo上生成了一个数据集并重命名了它。如果我注释掉var员工逻辑，我得到了我发布的问题，我不知道为什么EmpInfo需要LINQ选择

LINQ使用VARCHAR加入NVARCHAR

2 个答案: