How can i multiply value from notepad.txt file through c#

Question

 Hi, 

 

I want to do multiply with below code but where value i have fixed like 0.50 there i want to pick value from notepad.txt file so i can i do this.. please see below code.. and help me about that.. thanks.. 

 

int TotalSale = Convert.ToInt32(Total_sale_lbl.Text);

int Perc = Convert.ToInt32(Eighty_txt.Text);

if (Perc >= 95 && Perc <= 99)

{

bounus_txt.ForeColor = Color.Green;

bounus_txt.Text = (TotalSale / 100 * 0.50).ToString("0");

}