using System;

public class Program

{

    public static string ForceRelativeUrl(this Uri uri) => uri.IsAbsoluteUri?uri.PathAndQuery:uri.OriginalString;

    public static void Main()

    {   

        var loginUri_abs = new Uri("https://trader.iforex.com/webpl3/Account/Login?ReturnUrl=%2Fwebpl3%2FHandlers%2FClientState%2FClientState.ashx%3FmethodName%3DGetData%26requestMode%3D1%26csmg%3D5536520f-151e-469c-b294-6473d79c44de%26rnd%3D0.1387103519768451");

        var loginUri_rel = new Uri("/webpl3/Account/Login?ReturnUrl=%2Fwebpl3%2FHandlers%2FClientState%2FClientState.ashx%3FmethodName%3DGetData%26requestMode%3D1%26csmg%3D5536520f-151e-469c-b294-6473d79c44de%26rnd%3D0.1387103519768451");

        Console.WriteLine(loginUri_abs.PathAndQuery);

        Console.WriteLine(loginUri_rel.PathAndQuery);

    }

}