title: Why does my event run twice?
body: <p>I have a button </p>
  
  <pre><code> &lt;asp:Button ID="Button1" runat="server" Text="Button"  onclick="Button1_Click" UseSubmitBehavior="False" /&gt;
  </code></pre>
  
  <p>and my event is </p>
  
  <pre><code>Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
          Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("Document_RecordConnectionString1").ToString())
          con.Open()
          Dim del As New SqlCommand(" delete from TableA where RefNo = '" &amp; Request.QueryString("RefNo") &amp; "'", con)
          del.ExecuteNonQuery()
          For i As Integer = 0 To displayCBL.Items.Count - 1
  
              If displayCBL.Items(i).Selected Then
                  Dim cmd As New SqlCommand("Insert into TableA (RefNo,Text,InsertDate) values('" &amp; Request.QueryString("RefNo") &amp; "','" &amp; displayCBL.Items(i).Value &amp; "',getdate())", con)
                  cmd.ExecuteNonQuery()
  
              End If
          Next
          con.Close()
  End Sub
  </code></pre>
  
  <p>I notice my sub routine run twice hence insert data twice(Both debugger and SQL Server profiler confirm this). Is there something I miss?</p>