AsyncFileUpload does not partial postback even using update panel?

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ASP.NET

Ajax

C#3.5

C#5.0

//My problem is the two asyncFileUpload Control can't get partial postback ?
//How should i solve this?
//Thanks

<table>
<tr>
<td>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<contenttemplate> <asp:TextBox ID="txtID1" runat="server" AutoPostBack="True" />
<asp:RequiredFieldValidator ID="ValitxtID1 runat="server" ID" ControlToValidate="txtID1" Display="None" />
</contenttemplate>

</td>
</tr>
<tr>
<td>
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
<contenttemplate>
<ajax:AsyncFileUpload ID="fileUpload1"  runat="server" />
</contenttemplate>

</td>
</tr>

<tr>
<td>
<asp:UpdatePanel ID="UpdatePanel3" runat="server">
<contenttemplate>
<ajax:AsyncFileUpload ID="fileUpload2"  runat="server" />
</contenttemplate>

</td>
</tr>


</table>