C# Recursive Query

Since you have this data in your SQL Server database, one possible approach would be CTE's with recursion. This explanation looks a little confusing at first, but I think if you scroll down to the example it will be clear how to do this.

Without repeating the entire explanation here, this is an example of such a query:

USE AdventureWorks2008R2;
GO
WITH DirectReports (ManagerID, EmployeeID, Title, DeptID, Level)
AS
(
-- Anchor member definition
    SELECT e.ManagerID, e.EmployeeID, e.Title, edh.DepartmentID, 
        0 AS Level
    FROM dbo.MyEmployees AS e
    INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
        ON e.EmployeeID = edh.BusinessEntityID AND edh.EndDate IS NULL
    WHERE ManagerID IS NULL
    UNION ALL
-- Recursive member definition
    SELECT e.ManagerID, e.EmployeeID, e.Title, edh.DepartmentID,
        Level + 1
    FROM dbo.MyEmployees AS e
    INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
        ON e.EmployeeID = edh.BusinessEntityID AND edh.EndDate IS NULL
    INNER JOIN DirectReports AS d
        ON e.ManagerID = d.EmployeeID
)
-- Statement that executes the CTE
SELECT ManagerID, EmployeeID, Title, DeptID, Level
FROM DirectReports
INNER JOIN HumanResources.Department AS dp
    ON DirectReports.DeptID = dp.DepartmentID
WHERE dp.GroupName = N'Sales and Marketing' OR Level = 0;
GO

You could create a dictionary with RequestedUrl as the key and RedirectedUrl as the value. So once you find the requestedUrl you could find its redirectedURL and if that redirectedURL has a redirectedURL, you could find that too.

If I get you right, you want a neat small C# function to find the last redirection, right? In that case this should do it:

string GetRedirectionFromDatabase(string requestUrl)
{
  // Fetch redirect form DB, or if none exists return null
}

string GetFinalUrl(string requestUrl)
{
  var redirection = GetRedirectionFromDatabase(requestUrl);
  return redirection != null ? GetFinalUrl(redirection) : requestUrl;
}