song-of-the-day/song_of_the_day/SongValidators/UriBasedSongValidatorBase.cs

using System.Text.RegularExpressions;

public abstract class UriBasedSongValidatorBase : SongValidatorBase
{
    public abstract string UriValidatorRegex { get; }

    public override bool CanValidateUri(Uri songUri)
    {
        var regexp = new Regex(UriValidatorRegex, RegexOptions.IgnoreCase);
        return regexp.Match(songUri.ToString()).Success;
    }
}