Am I inadmissible to Canada?

You really should speak with an experienced attorney, but based upon a basic reading of the CIC website, it seems very likely that you will be deemed criminally inadmissible.  See http://www.cic.gc.ca/english/visit/faq-inadmissibility.asp for a description of the basics of this.

The attorney's advice is probably as definitive as it gets . . . except if you have a certified copy of the court's record of disposition clearly showing that the charge has been dismissed, that will work best.

If the charge is still in a conditional status, such as it is dismissed pending the occurrence of certain events, such as the completion of a period of good behavior, that is problematic. That amounts to a pending charge. Inadmissibility is primarily based on what the offence is (and its Canadian equivalent in particular) for which one was convicted, but pending charges for which the equivalent is an indictable offence in Canada (remembering that even though the charge can be and usually is charged as a summary offence in Canada, if it can be charged as an indictable offence, for immigration purposes it is an indictable offence) then there is a significant chance of being turned back at the border.

Actual admission to Canada is discretionary. The officer at the POE may allow entry even with something like this on your record. The officer at the POE may decide to not allow entry based on a variety of reasons even if you are not technically inadmissible. So no one can give you an absolute, oh yes, for sure you will be allowed into Canada answer.

But if you have a copy of the court's record of disposition, and especially if that is a certified copy (something that is worth having in your records anyway), and that shows the charge as dismissed, probably no problem related to this.

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