Page is loading internally autometically on button click

Dim chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
       Dim random = New Random()
       Dim result = New String(Enumerable.Repeat(chars, 5).[Select](Function(s) s(random.[Next](s.Length))).ToArray())
       'TextBox1.Text = result.ToString()
       Dim flag As Integer = 0
       Dim con As SqlConnection = New SqlConnection("Initial Catalog = ibs;Data Source = localhost;Persist Security Info=True;Integrated Security = True;")
       con.Open()
       Dim cmd As SqlCommand = New SqlCommand("insert into t1 values ('" + result + "','" + flag + "')", con)
       Dim i As Integer = cmd.ExecuteNonQuery()
       If i > 0 Then
           Response.Write("<script LANGUAGE='JavaScript'>alert('" + result + "')</script>")
       End If