Ashley Tisdale recently tied the knot with musician Christopher French at a private estate in Santa Barbara, California on September 8. Several celebrities attended the intimate wedding, but Tisdale's close friend and fellow 'High School Musical' star Zac Efron was absent from the milestone event.

Aside from the 'Charlie St. Cloud' actor, almost the entire cast of Disney's 'High School Musical' was in attendance at the wedding where Efron's former girlfriend for five years Vanessa Hudgens served as a bridesmaid.

Zac Efron was apparently unable to attend Tisdale's wedding because he's been away filming a most recent project.

Despite his absence, he did send her a congratulatory tweet that read, "Congrats Ash and Chris!."

Tisdale's fans were reportedly disappointed with Efron's nonattendance. Some fans criticized Efron for not taking some time off to attend a friend's wedding and support his once long-time girlfriend.

In August, Efron was also absent from a small 'High School Musical' dinner reunion in Los Angeles. The dinner was dodged because he was filming 'We Are Your Friends'; it was attended by Tisdale, Hudgens, Monique Coleman, Corbin Bleu, director Kenny Ortega and choreographer Chucky Klapow.

Although he missed off-camera 'High School Musical' cast reunions, Efron stated that we will be more than willing to work with his fellow actors in a future Disney movie.

"We're all thinking about it. I continue to see all the guys from High School. Every time we do...there's just this look between us. It's so cool because we never forget a single moment of that experience. It brings you right back to those days," Efron said in an interview with E! News.

Meanwhile, talk of a 'High School Musical' reunion excites "Zanessa" fans, since the possible reunion is another opportunity for Hudgens and the recently single Efron to reunite once again.

On a side note, Efron recently ended his relationship with 'Fast & Furious' actress Michelle Rodriguez who is 10 years his senior.