I have a drop down list contain "Add" and "Subtract". When user select either one, it will call a function Calculate()

private int Calculate(string sAction)
{
   int iTotal = 0;
   if(sAction == "Add")
   {
       iTotal = X + Y;
   }
   else if(sAction == "Subtract")
   {
      iTotal = X-Y;
   }       
   return iTotal;
}

I do not wish to hard coded it to compare the action. It seem like not fulfill Open Closed Principle. If I change the text in the drop down list, I need to change the function as well. May I know how I can improve this code? Thanks.

I have a drop down list contain "Add" and "Subtract". When user select either one, it will call a function Calculate()

private int Calculate(string sAction)
{
    int iTotal = 0; 

    if(sAction == "Add")
    {
        iTotal = X + Y;
    }
    else if(sAction == "Subtract")
    {
       iTotal = X-Y;
    }      

    return iTotal;
}

I do not wish to hard coded it to compare the action. It seem like not fulfill Open Closed Principle. If I change the text in the drop down list, I need to change the function as well. May I know how I can improve this code?