using System;

using System.Globalization;

​

public class Program

{

    public static Uri CanonicalAuthority;

    public static void Main()

    {

        Uri uri = new Uri("https://dummy.b2clogin.com/dummy.onmicrosoft.com/b2c_1a_signup_signin_staging/oauth2/authorize/where/did/you/go");

        GetAuthority(uri);

        Console.WriteLine(CanonicalAuthority);

    }

​

    private static string[] GetPathSegments(string absolutePath)

    {

        string[] pathSegments = absolutePath.Substring(1).Split(new[]{'/'}, StringSplitOptions.RemoveEmptyEntries);

        return pathSegments;

    }

​

    private static void GetAuthority(Uri authorityUri)

    {

        string[] pathSegments = GetPathSegments(authorityUri.AbsolutePath);

        if (pathSegments.Length < 3)

        {

            throw new ArgumentException("B2C 'authority' Uri should have at least 3 segments in the path (i.e. https://<host>/tfp/<tenant>/<policy>/...). ");

        }

​

        CanonicalAuthority = new Uri(string.Format(CultureInfo.InvariantCulture, "https://{0}/{1}/{2}/{3}/", authorityUri.Authority, pathSegments[0], pathSegments[1], pathSegments[2]));

    }

}