Linq to SQL query to get all the descendats in c#

This has been modified by me from a earlier question that was answered by the knowledgeable developer VULPES, This answer should satisfy you needs,


Note a couple of problems exist in your table it would be easy to create a circular relationship referring to one person reports to another and the other reports back to the person, in the following example level keeps this from happening if you only want to go 3 levels deep then pass in 3,  This example was written using linq to objects however it really easy for you to take it and build a linq to sql dll to reference,

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output  when you want to see the first 3 levels that report to Gandhi

Gandhi-Gandhi
Gobind-Gobind
Gobind-Gobind
JK-JK
KP-KP
KP-KP
Prem-Prem

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void main()
{
 
List employees = new List
{

new Employee("Gandhi", "Gandhi", null),
new Employee("Prem", "Prem", "Gandhi"),
new Employee("JK", "JK", "Gandhi"),
new Employee("Gobind", "Gobind", "Prem"),
new Employee("KP", "KP", "Prem"),
new Employee("Venkat", "Venkat", "Goind"),
new Employee("Niyam", "Niyam", "Goind"),
new Employee("Aashiq", "Aashiq", "KP"),
new Employee("James", "James", "KP"),
new Employee("Linu", "Linu", "Venkat"),
new Employee("Mathi", "Mathi", "Niyam"),
new Employee("Karthik", "Karthik", "Niyam"),

new Employee("Vignesh", "Vignesh", "Aashiq"),
new Employee("Gobind", "Gobind", "Prem"),
new Employee("KP", "KP", "Prem"),
new Employee("Venkat", "Venkat", "Goind"),
new Employee("Niyam", "Niyam", "Goind"),
new Employee("Aashiq", "Aashiq", "KP"),
new Employee("James", "James", "KP"),
new Employee("Linu", "Linu", "Venkat"),
new Employee("Karthik", "Karthik","Niyam"),
new Employee("Vignesh", "Vignesh","Aashiq"),

new Employee("KK", "KK","Aashiq"),
new Employee("Antony", "Antony","James"),
new Employee("Dhanesh", "Dhanesh","Aashiq"),
new Employee("Anitha", "Anitha","Linu"),
new Employee("Manu", "Manu","Mathi"),
new Employee("Babu", "Babu","Mathi"),
new Employee("Kavya", "Kavya","Karthik"),
new Employee("Subbu", "Subbu","Karthik"),
new Employee("Sanjeev", "Sanjeev","KK"),
new Employee("Periyannan", "Periyannan","Antony"),
new Employee("Karthi", "Karthi","Antony"),
new Employee("Prakash", "Prakash","Dhanesh"),
new Employee("XXXX", "XXXX", "Prakash"),
new Employee("YYYY", "YYYY", "Prakash")
};
var children = GetChildren(employees, "Gandhi", 3);
foreach(Employee child in children)
{
Console.WriteLine("{0}-{1}", child.Id, child.Name);
}
Console.Read();
}
static IEnumerable GetChildren(IEnumerable persons, string id, int level)
{
if (level < 1) level = 1;
var parent = persons.Where(p => p.Id.Equals(id));

if (parent.Count() == 0) return Enumerable.Empty();

if (level == 1) return parent;

var children = GetChildren2(persons, parent.First().Id, level - 1);

if (children.Count() == 0) return parent;
return parent.Union(children).OrderBy(p => p.Id);
}
static IEnumerable GetChildren2(IEnumerable persons, string id, int level)
{
var children = persons.Where(p =>p.ParentId != null && p.ParentId.Equals( id));
if (children.Count() == 0) return Enumerable.Empty();
if (level == 1) return children;
IEnumerable results = children;

foreach(Employee c in children)
{
var grandChildren = GetChildren2(persons, c.Id, level - 1);
if(grandChildren.Count() > 0)
{
results = results.Union(grandChildren);
}
}
return results;

}

public class Employee
{
public string Id {get; set;}
public string Name {get; set;}
public string ParentId {get; set;}

public Employee(string id, string name, string parentId)
{
Id = id;
Name = name;
ParentId = parentId;
}


}
// Define other methods and classes here