Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
   Label1.Text="You clicked a button"
End Sub

public void Button1_Click (object sender, System.EventArgs e)
{
   Label1.Text="You clicked a button.";
}

Private Sub Page_Load(ByVal Sender As System.Object, ByVal e _
    As System.EventArgs) Handles MyBase.Load
    If Not IsPostback Then
        ' This is called the first time the page has loaded.
        ' The user will not have been able to click any buttons yet.
    Else
        ' This is called if the form has been posted back, possibly
        ' by a button click.
        Me.Label1.Text = "You clicked a button."
    End If
End Sub

private void Page_Load(object sender, System.EventArgs e)
{
   if (!IsPostBack)
   {
      // Evals true first time browser hits the page.
   }
   else
   {
      // This is called if the form has been posted back, possibly
      // by a button click.
      this.Label1.Text = "You clicked a button.";
   }
}

' Set the CommandName property of the buttons to "Add", 
' "Subtract", "Multiply", and "Divide".
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
   AddHandler Me.btnAdd.Click, AddressOf Calculate
   AddHandler Me.btnSubtract.Click, AddressOf Calculate
   AddHandler Me.btnMultiply.Click, AddressOf Calculate
   AddHandler Me.btnDivide.Click, AddressOf Calculate
End Sub

Public Sub Calculate(ByVal sender As Object, ByVal e As System.EventArgs)
   Dim op1 As Integer = CType(Me.TextBox1.Text, Integer)
   Dim op2 As Integer = CType(Me.TextBox2.Text, Integer)
   Dim result As Integer
   Select Case CType(sender, Button).CommandName
      Case "Add"
         result = op1 + op2
      Case "Subtract"
         result = op1 - op2
      Case "Multiply"
         result = op1 * op2
      Case "Divide"
         ' Divide two numbers and return an integer result.
         If op2 > 0 Then
               result = op1 \ op2
         Else
               result = 0
         End If
      Case Else
         ' Error handling code here.
   End Select
   Label1.Text = result.ToString()     
End Sub

// Set the CommandName property of the buttons to "Add", _
// "Subtract", "Multiply", and "Divide".
protected void Page_Load(object sender, EventArgs e)
{
   btnAdd.Click += new System.EventHandler(this.Calculate);
   btnSubtract.Click += new System.EventHandler(this.Calculate);
   btnMultiply.Click += new System.EventHandler(this.Calculate);
   btnDivide.Click += new System.EventHandler(this.Calculate);
}

protected void Calculate (object sender, System.EventArgs e)
{
   int op1 = Convert.ToInt16(TextBox1.Text);
   int op2 = Convert.ToInt16(TextBox2.Text);
   int result = 0;
   switch(((Button)sender).CommandName)
   {
      case "Add" :
         result = op1 + op2;
         break;
      case "Subtract" :
         result = op1 - op2;
         break;
      case "Multiply" :
         result = op1 * op2;
         break;
      case "Divide" :
         // Integer division.
         if (op2 > 0) 
               result = op1 / op2;
         else
               result = 0;
         break;
      default:
         // Error handling code here.
         break;
   }
   Label1.Text = result.ToString();
}