Hi,
I have page with fields and upload button. First field is Id, which is for new records 0. After first save I update it's value to real Id. It works fine until I Add FileUploadField.

I create sample, to reproduce a problem try click save button multiple times. Value should change only first time. 

<script runat="server">
    protected void SaveData(object sender, Ext.Net.DirectEventArgs e)
    {
        if (Id.Text == "0" || this.Id.Text == string.Empty)
        {
            Id.Value = DateTime.Now.Ticks;
        }
    }
</script>

<!DOCTYPE html>
<html>
<head runat="server">
    <title>Field persistence test</title>
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <ext:ResourcePlaceHolder runat="server" Mode="ScriptFiles" />
	<ext:ResourcePlaceHolder runat="server" Mode="Style" />    
</head>
<body>
    <form runat="server">
    <ext:ResourceManager runat="server" locale="cs-CZ" 
        viewstatemode="Disabled" ajaxviewstatemode="Disabled" enableviewstate="false" />    
    <ext:Window 
        id="mainWindow"
        runat="server" 
        maximized="true"
        maximizable="false"
        closable="false"
        plain="true"
        border="false"
        BodyBorder="false"
        Resizable="false"
        autoscroll="true"
        modal="true">        
        <topbar>
            <ext:Toolbar runat="server">
                    <Items>
                        <ext:TabStrip runat="server" id="tabs">
                            <Items>
                                <ext:TabStripItem actionitemid="pnlSummary" title="Souhrn" icon="BookOpen" />                                
                            </Items>
                        </ext:TabStrip>
                        <ext:ToolbarFill runat="server" />                       
                        <ext:button runat="server" icon="Disk" ondirectclick="SaveData" />
                        <ext:FileUploadField runat="server" ButtonOnly="true" id="ImportFile" 
                            buttontext="Import" Icon="PageWhiteGet" visible="true" />                                                 
                    </Items>
                </ext:Toolbar>
        </topbar>
        <items>                        
            <ext:Panel ID="pnlSummary" runat="server" Header="false" frame="true">
                <items>
                    <ext:tablelayout runat="server" columns="2" >                        
                        <cells>
                            <ext:cell rowspan="2">
                                <ext:fieldset runat="server" >
                                    <items>
                                        <ext:numberfield id="Id" fieldlabel="Id" runat="server" hidden="false" 
                                            width="300" allowdecimals="false" disabled="true"
                                            IndicatorIcon="Information" Anchor="-20" IndicatorTip="Filled automatically"  />
                                        <ext:textfield id="Description" runat="server" fieldlabel="Popis" width="350" />
                                    </items>                            
                                </ext:fieldset>
                            </ext:cell>                          
                        </cells>
                    </ext:tablelayout>                                           
                </items>                     
            </ext:Panel>
        </items>
    </ext:Window>
    </form>
</body>
</html>