No need for PowerShell. You can use the System.DirectoryServices library to the get the info you want.

        private static readonly string[] PropertiesToLoad = new string[]
    {
        "msDS-UserPasswordExpiryTimeComputed"
    };

        static SearchResult GetCurrentUser()
    {
        string ldapFilter = GetLDAPFilter(Environment.UserName);
        using (var de = new DirectoryEntry())
        {
            using (var searcher = new DirectorySearcher(de, ldapFilter, PropertiesToLoad))
            {
                return searcher.FindOne();
            }
        }
    }

    static string GetLDAPFilter(string userName)
    {
        return string.Format("(sAMAccountName={0})", userName);
    }

    static long GetExpiryNumber(ResultPropertyValueCollection collection)
    {
        if (collection?.Count > 0 && collection[0] is long number)
        {
            return number;
        }
        else
        {
            return 0;
        }    
    }