public static List getChildId(int Parentid)
{
using (dbEntities dbcontext = new dbEntities())
{

List childid = new List(dbcontext.employee.Where(w => w.ParentId == Parentid).Select(w => w.Id));
foreach (var id in childid.ToList())
{
List childs = getChildId(id);
childid.AddRange(childs);
}
return childid;
}

}

CTE in SQL server is the result set like table.

e.g.
WITH Sales_CTE (SalesPersonID, NumberOfOrders)
AS
(
SELECT SalesPersonID, COUNT(*)
FROM Sales.SalesOrderHeader
WHERE SalesPersonID IS NOT NULL
GROUP BY SalesPersonID
)
SELECT AVG(NumberOfOrders) AS “Average Sales Per Person”
FROM Sales_CTE;
GO

ALTER TABLE [tablename] NOCHECK CONSTRAINT [FK_idconstraint]

ALTER TABLE [tablename] WITH CHECK CHECK CONSTRAINT [FK_idconstraint]

ALTER TABLE [tablename] DROP CONSTRAINT [FK_idconstraint]

ALTER TABLE [tablename] WITH NOCHECK ADD CONSTRAINT [FK_idconstraint] FOREIGN KEY(columnname)
REFERENCES <parent table here> (<parent column here>)
ON DELETE CASCADE