I have to say there is a lot of confusing information out there. Here is the deal, I have gone through it.
About 5 years ago I was on the wrong end and with a bad person and was charged with a misdemeanor. Did my probation, paid my fines and went to court. In the end my attorney requested dismissal of the charges due to me fulfilling my obligation and she requested change of plea to not guilty.
1. Charged
2. Paid my time
3. Request for changed of plea to innocent
4. Requested for dismissal

So the deal is that if you are a first timer and do what they ask, then they can change plea after and have dismissed. Then you get a paper from courts and your attorney stating that you have the legal right to say no on an application to :have you ever been convicted of a felony or misdemeanor?

Now down to the LIVESCAN/background check,
I applied for a job that just did a basic background...nothing there.
I applied for a childcare job that used LIVESCAN (which goes through a county agency) DOJ (dept. Of justice, FBI, etc) BANG there is was.
So there are many factors to the equations. Even if it is dismissed, expunged, the LIVE SCAN will show it. They will send you a packet to fill out regarding the charges and have you ask that it be excluded from consideration.

But, even though I was convicted and then plea changed and dismissed..IT STILL SHOWED UP> the jist of it, is be honest with your employer