让 FileUpload 文本框只读

让 FileUpload 文本框只读

<asp:FileUpload runat="server" style="height:20px;" unselectable="on" ID="fileUpdate" />

<asp:FileUpload runat="server" style="height:20px;" unselectable="on" ID="fileUpdate" />

<input type="file" id="fileUpdate" unselectable="on" size="20" >