bool column in where clause - linq/c#

Question

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

Will the above build me a query of this :

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

This is what I want to return

 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

The code above does not build the SQL query you posted, if that's what you're asking.

Unless I'm mistaken, you overwrite the value of employeeWhere twice. I think you need:

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

If you had input parameters (say bool myBoolParam and decimal myDecimalParam) to whatever method this is in, you could do something like this:

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

Answer 2

I think you want something like this:

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");