Create an array of your MenuStrip
MenuStrip[] mstrip = new MenuStrip[]
{
msO1,msO2, msO3, msP1, msP2, msP3 // add other menus here when needed
};
now you could work on the array as a Whole to make visible or not your menus
for(int x = 0; x < menus.Length; x++)
mstrip[x].Visible = false;
and your code could be simplified with
for (int x = 0; x < splt.Length; x++)
{
int menuIndex;
if(Int32.TryParse(splt[x], out menuIndex))
{
menuIndex--;
if(menuIndex >= 0 && menuIndex < mstrip.Length)
mstrip[menuIndex].Visible = true;
}
}
Remember, arrays indexes start at zero (while your user will probably start counting a 1).