IF Statement multiple conditions, same statement

Question

Hey all, looking to reduce the code on my c# if statements as there are several repeating factors and was wondering if a trimmer solution is possible.

I currently have 2

Answer 1

if (columnname != a 
  && columnname != b 
  && columnname != c
  && (checkbox.checked || columnname != A2))
{
   "statement 1"
}

Should do the trick.