<asp:Button ID="ServerCredentials" runat="server" Text="Server Credentials" Font-Names="Verdana" Font-Size="12px" OnClick="Credential_Click" Width="135px"/>

Protected Sub Credential_Click(ByVal sender As Object, ByVal e As System.EventArgs)
        Response.Redirect("~/WebPage/Booking/ExchangeServer.aspx")
    End Sub

<asp:Button ID="ServerCredentials" runat="server" Text="Server Credentials" Font-Names="Verdana" Font-Size="12px" OnClientClick="return CheckDateVonBis()"  OnClick="Credential_Click" Width="135px"/>

Server.TransferRequest("~/WebPage/Booking/ExchangeServer.aspx")

<asp:Button ID="ServerCredentials" runat="server" Text="Server Credentials" Font-Names="Verdana" Font-Size="12px" CausesValidation="False" OnClick="Credential_Click" Width="135px"/>