how can we put multiple else statements in c# code example

Example 1: multiple if statements c#

//the same rules that are in math, applies also in programming - 
 //the computer checks the statements surrounded with parentheses first
  //just like you do calculations with parentheses first :)
if((a == 0 || b == 0) && (x == 0 || y == 0))
{
  //if one of a or b equals 0 AND one of x or y equals 0 then this runs
}

Example 2: c# if statement with 2 conditions

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