DropDownList的SelectedValue的disapperaing上提交（未发行的IsPostBack！） [英] dropdownlist selectedvalue disapperaing on Submit (not IsPostBack issue!)

问题描述

我有状态的一个DropDownList当页面最初被加载（ddl_state）得到填充。我选择一个状态，然后点击提交按钮。我对btn_submit_Click方法的第一行一个断点。在Page_Load方法没有得到在此之前运行。在btn_submit_Click方法的第一行，ddl_state.SelectedValue的值是空字符串。我尝试设置的AutoPostBack将DropDownList为true（读这地方，并认为这可能有所作为），但随后在DropDownList的值只得到立即清除！

任何想法？

 ＆LT; ASP：DropDownList的ID =ddl_state=服务器
                                        元：获取ResourceKey =ddl_stateResource1＆GT;
                                    ＆LT; / ASP：DropDownList的＆GT;保护无效的Page_Load（对象发件人，EventArgs的发送）
    {
        如果（的IsPostBack）回报;        lbl_errors.Text =的String.Empty;
        lblVoucherRequired.Text =的String.Empty;        tb_name_addr_1.Focus（）;
        PopulateStates（）;
        PopulateFormFromSessionData（）;
    }保护无效btn_submit_Click（对象发件人，EventArgs的发送）
    {
        如果（！ValidateInput（））// ddl_state.SelectedValue这里是一个空字符串！
        {
            返回;
        }        SetSessionVariables（）;
 

解决方案

您的问题是，的ViewState 是禁用的。

这表明您的两个症状：

• 的DropDownList 与回传的AutoPostBack 已启用
之后清除

• 服务器不知道是什么的SelectedValue 的的DropDownList 是

检查web.config，页面和控件来检查，没有张师傅禁用ViewState中。

DISABLE VIEWSTATE

I have a DropDownList of states getting populated when the page initially gets loaded (ddl_state). I select a state, then click the Submit button. I have a breakpoint on the first line of the btn_submit_Click method. The Page_Load method is not getting run prior to this. On the first line of the btn_submit_Click method, the value of ddl_state.SelectedValue is an empty string. I tried setting AutoPostBack of the dropdownlist to true (read this somewhere and thought it might make a difference), but then the values in the dropdownlist just get cleared immediately!

Any ideas?

<asp:DropDownList ID="ddl_state" runat="server" 
                                        meta:resourcekey="ddl_stateResource1">
                                    </asp:DropDownList>

protected void Page_Load(object sender, EventArgs e)
    {
        if (IsPostBack) return;

        lbl_errors.Text = string.Empty;
        lblVoucherRequired.Text = string.Empty;

        tb_name_addr_1.Focus();
        PopulateStates();
        PopulateFormFromSessionData();
    }

protected void btn_submit_Click(object sender, EventArgs e)
    {
        if (!ValidateInput()) // ddl_state.SelectedValue is an empty string here!!!
        {
            return;
        }

        SetSessionVariables();

解决方案

Your issue is that ViewState is disabled.

This is indicative of both of your symptoms:

• DropDownList clears after postback with AutoPostBack is enabled
• Server does not know what the SelectedValue of the DropDownList is

Check the web.config, page, and control to check that none of them are disabling viewstate.

DISABLE VIEWSTATE

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