public override void Validate(string input, string field)
{
if (String.IsNullOrEmpty(input) || String.IsNullOrWhiteSpace(input))
{
throw new Exception($"The field '{field}' may not be empty.");
}
if (Feed.CheckIfChannelURLExist(input, FeedList))
{
throw new Exception($"Channel with that URL is already added");
}
if (!Uri.IsWellFormedUriString(input, UriKind.Absolute))
{
throw new Exception($"Entry of field '{field}' is not a valid RSS URL.");
}
}