Assalam O Alikum Sir i am facing error to watching videos and they cannot play, error giving below

System.ArgumentOutOfRangeException: startIndex cannot be larger than length of string. Parameter name: startIndex at PlayVideo.GetVidID(String rawURL) in D:\LMS\CourseNavigation\PlayVideo.aspx.vb:line 510 at PlayVideo.LoadVideo(String strVideoId) in D:\LMS\CourseNavigation\PlayVideo.aspx.vb:line 114