c# - FileUpload 在多 View 和更新面板中不起作用

Question

<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel runat="server">
<Triggers>
<asp:PostBackTrigger ControlID="Button1" />
</Triggers>
    <ContentTemplate>

<asp:MultiView ID="MultiView1" runat="server" 
                 ActiveViewIndex="0">           
    <asp:View ID="View1" runat="server">
        <asp:Button Text="next"
            runat="server" onclick="Unnamed1_Click" />
    </asp:View>
    <asp:View ID="View2" runat="server">
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" 
        style="width: 56px" />
    <asp:FileUpload ID="fileupload2" runat="server" />
    </asp:View>
</asp:MultiView>
 </ContentTemplate>
</asp:UpdatePanel>

后面的代码是

 protected void Button1_Click(object sender, EventArgs e)
    {
        if (fileupload2.HasFile)
        {
            //code..
        }
    }
    protected void Unnamed1_Click(object sender, EventArgs e)
    {
        MultiView1.ActiveViewIndex = 1;
    }

当我第一次点击 Button1 上传图片时，fileupload2.HasFile 返回“false”

在不刷新页面的情况下再次尝试上传相同的图片，然后 fileupload2.HasFile 返回“true”

在 View1 中正常工作。问题出在 View 2

上传文件有什么问题？

Answer 1

尝试使用 RegisterPostBackControl 注册按钮控件在页面生命周期的早期:

   protected void Page_Init(object sender, EventArgs e)
   {
       ScriptManager1.RegisterPostBackControl(Button1);
   }

另请参阅:

FileUpload and UpdatePanel: ScriptManager.RegisterPostBackControl works the second time.