Hierarchy from Flat Data

Question

I have an employee class that has an employeeId (int), parent(int) and children property List. I get the employee list from the database in the

Answer 1

You can start by creating a list of all the employee objects and setting the EmployeeId and ParentId properties. If you also put them in a dictionary, keyed by EmployeeId, you can retrieve the parent of each afterward to add to the Children collection:

List employees = new List();
Dictionary dict = new Dictionary();

foreach(result from database query)
{
   Employee employee = new Employee();
   employee.EmployeeId = result["EmployeeId"];
   employee.ParentId = result["ParentId"];
   employees.Add(employee);
   dict.Add(employee.EmployeeId, employee);
}

foreach(Employee e in employees)
{ 
  dict[e.ParentId].Children.Add(e);
}