example.cs

if (condition 1)
{
  if (condition 2)
  {
     // executed if conditions 1 & 2 are true
  }
  else
  {
    // executed if condition 1 is true & condition 2 is false
  }
}
else
{
  if (condition 3)
  {
    // executed if condition 1 is false & condition 3 is true
  }
  else
  {
    // executed if condition 1 is false & condition 3 is false
  }