public partial class frmHesapMakinesi : Form 
      { 
          public frmHesapMakinesi() 
          { 
              InitializeComponent(); 
          } 
   
          private void IslemiSec(object sender, System.EventArgs e) 
          { 
               
              Button btnIslem = (Button)sender; 
              string Islem = btnIslem.Text; 
   
              try 
              { 
                  if (IsValidData())      
                  { 
                      double sayi1 = Convert.ToDouble(txtsayi1.Text); 
                      double sayi2 = Convert.ToDouble(txtsayi2.Text); 
                      double sonuc = Hesapla(sayi1, Islem, sayi2); 
                      sonuc = Math.Round(sonuc, 4); 
                      this.lblsonuc.Text = sonuc.ToString(); 
                  } 
              } 
              catch (Exception ex) 
              { 
                  MessageBox.Show(ex.Message + "\n\n" + ex.GetType().ToString() + "\n" + 
                          ex.StackTrace, "Exception"); 
                  txtsayi2.Focus(); 
              } 
          } 
   
          private double Hesapla(double sayi1, string Islem, double sayi2) 
          { 
              double sonuc = 0; 
               
              
   
              switch (Islem) 
              { 
                  case "+": 
                      sonuc = sayi1 + sayi2; 
                      break; 
                  case "-": 
                      sonuc = sayi1 - sayi2; 
                      break; 
                  case "*": 
                      sonuc = sayi1 * sayi2; 
                      break; 
                  case "/": 
                      if (sayi2 == 0) 
                          throw new Exception("Gecersiz islem. Sifira bolemezsiniz!"); 
                      else 
                          sonuc = sayi1 / sayi2; 
                      break; 
                  default: 
                      break; 
              } 
              return sonuc; 
   
          } 
   
          public bool IsValidData() 
          { 
              return 
                  // Validate the Score text box 
                  Validator.IsPresent(txtsayi1, "Operand 1") && 
                  Validator.IsDouble(txtsayi1, "Operand 1") && 
                  Validator.IsWithinRange(txtsayi1, "Operand 1", 0, 1000000) && 
                  // Validate the sayi2 text box 
                  Validator.IsPresent(txtsayi2, "Operand 2") && 
                  Validator.IsDouble(txtsayi2, "Operand 2") && 
                  Validator.IsWithinRange(txtsayi2, "Operand 2", 0, 1000000); 
          } 
   
   
          private void btnExit_Click(object sender, System.EventArgs e) 
          { 
              this.Close(); 
          } 
   
          
          private void Clearsonuc(object sender, System.EventArgs e) 
          { 
              this.lblsonuc.Text = ""; 
          } 
      }