RadioButton sorunu

<table class="style1"> 
                              <tr> 
                                  <td> 
                                      Şekil :</td> 
                                  <td> 
                                      <asp:RadioButton ID="RadioButton1" runat="server"  
                                          Text="Dikdörtgen (veya Kare)" /> 
   <asp:RadioButton ID="RadioButton2" runat="server" Text="Üçgen" /> 
                                  </td> 
                              </tr> 
                              <tr> 
                                  <td> 
                                      Taban Uzunluğu (a) :</td> 
                                  <td> 
                                      <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> 
                                  </td> 
                              </tr> 
                              <tr> 
                                  <td> 
                                      Yükseklik (h) :</td> 
                                  <td> 
                                      <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox> 
                                  </td> 
                              </tr> 
                              <tr> 
                                  <td> 
                                       </td> 
                                  <td> 
                                      <asp:Button ID="Button1" runat="server" Text="Hesapla" /> 
   <asp:Label ID="Label1" runat="server"></asp:Label> 
                                  </td> 
                              </tr> 
                          </table>

Public Partial Class alan_hesaplama 
      Inherits System.Web.UI.Page 
   
      Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
   
      End Sub 
   
      Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click 
          If RadioButton1.Checked Then 
              Label1.Text = "<strong>Dikdörtgenin Alanı = " & Val(TextBox1.Text) * Val(TextBox2.Text) & " cm²</strong>" 
          ElseIf RadioButton2.Checked Then 
              Label1.Text = "<strong>Üçgenin Alanı = " & Val(TextBox1.Text) * Val(TextBox2.Text) / 2 & " cm²</strong>" 
          End If 
      End Sub 
  End Class