Parse URL using Regex

Question

I have Youtube and Dailymotion Video URL as follows:

For Youtube

• http://www.youtube.com/v/0PsnoiwMrhA
• http://www.youtube.com/watch?v=ok_VQ8I7g6I
• http://www.youtube.com/watch?v=1taai0d1FXw&list=PL1uGXsv9VLdCm_LYVa9c7Rv8DPdflJZfT

For Dailymotion

• http://www.dailymotion.com/video/x21a1i8_brazil-1-7-germany-a-world-cup-2014-brick-by-brick-video-animation_news
• http://www.dailymotion.com/video/x2148xg_brazil-1-7-germany-brazil-player-ratings-from-a-shocking-defeat_sport

I want to get the Preview image of these video, So i have to parse these link as follows:

For Youtube

• http://img.youtube.com/vi/0PsnoiwMrhA/default.jpg
• http://img.youtube.com/vi/ok_VQ8I7g6I/default.jpg
• http://img.youtube.com/vi/1taai0d1FXw/default.jpg

For Dailymotion

• http://www.dailymotion.com/thumbnail/video/x21a1i8_brazil-1-7-germany-a-world-cup-2014-brick-by-brick-video-animation_news
• http://www.dailymotion.com/thumbnail/video/x2148xg_brazil-1-7-germany-brazil-player-ratings-from-a-shocking-defeat_sport

Please help me. I'm newbie in regex...

Answer 1

YouTube:

ResultString = Regex.Replace(SubjectString, "http.*?v[=/]([^\s&#]+)\S+", "http://img.youtube.com/vi/$1/default.jpg", RegexOptions.IgnoreCase)

DailyMotion:

A simple string replace would do, but here is the regex:

ResultString = Regex.Replace(SubjectString, "http://www\.dailymotion\.com/video/", "http://www.dailymotion.com/thumbnail/video/", RegexOptions.IgnoreCase)