Question

 Expression<Func<Employee, bool>> employeeWhere = R => true;
 employeeWhere = R => R.PositionCode == "M";
 employeeWhere = R => R.IsActive; //want only ones which are true

以上是否构建了对此的查询：

SELECT * FROM EMPLOYEE 
WHERE POSITIONCODE = "M" && IsActive = 1

这就是我要归还的内容

 var result = _db.Employees
              .Where(employeeWhere)
              .Select(p => new { p.EmployeeID, p.FName, p.MName, p.LName })
              .AsEnumerable()
              .ToDictionary(kvp => kvp.EmployeeID, kvp => kvp.FName + " " + kvp.MName + " " + kvp.LName);

        return new SelectList(result, "Key", "Value");

Answer 1

上面的代码不构建您发布的SQL查询，如果这就是您所要求的。

除非我弄错了，否则你会两次覆盖employeeWhere的价值。我想你需要：

Expression<Func<Employee, bool>> employeeWhere = R => R.PositionCode == "M" && R.IsActive;

如果你有输入参数（例如 bool myBoolParam 和十进制myDecimalParam ），那么你可以这样做：

Expression<Func<Employee, bool>> employeeWhere =
    (R => R.PositionCode == "M" && R.IsActive && myBoolParam && R.Salary > myDecmialParam);

Answer 2

我想你想要这样的东西：

var query = from e in _db.Employees
            where e.PositionCode == "M" && e.IsActive
            select new { e.EmployeeID, 
                Value = e.FName + " " + e.MName + " " + e.LName                 
            };

return new SelectList(query.ToDictionary(x => x.EmployeeID, "Key", "Value");

where子句中的bool列 - linq / c＃

2 个答案: