C# 如何在视图状态下维护用户控件值？

我想在视图状态下维护用户控件值

我试过文本框，下拉值在视图状态下保持不变

但BasicDatePicker值未在视图状态下维护，我得到的是null值

代码：

.aspx

在下图中，当我给出文本框、下拉列表和日期选择器时，我单击添加按钮控件添加文本框，下拉列表值在那里，但日期选择器值消失

---

有什么想法吗？提前感谢

您可以将该值存储在一个隐藏控件中，并在回发时将该值恢复到相应的控件中，如果涉及jquery（我猜是这样的），那么它在回发时通常会忘记它的值，而不管是否启用了viewstate等

查看如何使用隐藏字段值将datapicker值设置为ready

以下是上述博客文章中的代码：

<table>
<tr>
    <td>
        <asp:CheckBox ID="chkEnableMonthlyNotifications" runat ="server" CssClass="cell-Text" Text="Enable monthly notifications." />
        <br/>
    </td>
</tr>
<tr>
    <td>
        <label for="txtMonthStartDate">Specify start date for monthly notification</label>
        <br />
        <br />
        <asp:TextBox ID="txtMonthStartDate" runat="server" Enabled="true"></asp:TextBox>
        <asp:HiddenField ID="hdnMonthStartDate" runat="server" />
    </td>
</tr>
<tr>
    <td>
        <label for="txtMonthEndDate">Specify end date for monthly notification, or leave blank if no end date.</label>
        <br />
        <br />
        <asp:TextBox ID="txtMonthEndDate" runat="server" Enabled="true" > </asp:TextBox>
        <asp:HiddenField ID="hdnMonthEndDate" runat="server" />
    </td>
</tr>
</table>

用于在document.ready上再次设置日期选择器日期的jQuery代码

$(document).ready(function ()
{
  //Initializing the datepicker

  $("[id$=_txtMonthStartDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnMonthStartDate]' });

  //Code to set the datepicker's date again after post back
  if(!($("[id$=_txtMonthStartDate]").attr("Value") == undefined))
  {
    if($("[id$=_txtMonthStartDate]").attr("Value").length > 0)
    {
        $("[id$=_txtMonthStartDate]").datepicker("setDate",new Date($("[id$=_txtMonthStartDate]").val($("[id$=_txtMonthStartDate]").attr("Value"))));
    }
  }
}

---

所以，这段代码会和你的有点不同，但我知道它是有效的。我已经在这里工作了好几个星期了。我已经完成了预渲染、创建viewstate和加载viewstate。每当我的某个值发生更改时，我都会将其保存到已设置的私有属性中

    //Global ViewState Variables
    private DataTable networksInfo;
    private string HHmm;
    private string Window;
    private string ZoomFactorTop;
    private string ZoomFactorBottom;
    protected Boolean autoRefresh; 

    /// <summary>
    /// This page prerender allows me to save viewstate objects before anything bad
    /// happens. It's going to save any data that needs to persist across postbacks,
    /// since the page refreshes with an autorefresh. Whenever updated, the ViewState
    /// will also need to be updated.
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    void Page_PreRender(object sender, EventArgs e)
    {
        // Save the ViewStateObjects before the page is rendered.
        ViewState.Add("networksListVS", networksInfo);
        ViewState.Add("HHmmVS", HHmm);
        ViewState.Add("WindowVS", Window);
        ViewState.Add("ZoomFactorTopVS", ZoomFactorTop);
        ViewState.Add("ZoomFactorBottomVS", ZoomFactorBottom);
        ViewState.Add("AutoRefresh", autoRefresh);
    }

    protected void Create_ViewState(DateTime now)
    {
        //Populate Dropdown handles the initial value for networksInfo, but none of the others are

        //Set ViewState Vars' initial values
        if (ViewState["HHmmVS"] == null)
        {
            int HH = now.Hour;
            int mm = now.Minute;

            Change_Time(HH, mm);

        }
        if (ViewState["WindowVS"] == null)
        {
            //The default time window to view is 6 hours
            Window = "6";
        }
        if (ViewState["ZoomFactorTopVS"] == null)
        {
            //The default zoom factor is Window + 0
            ZoomFactorTop = "0";
        }
        if (ViewState["ZoomFactorBottomVS"] == null)
        {
            //The default zoom factor is Window + 0
            ZoomFactorBottom = "0";
        }
        if(ViewState["AutoRefresh"] == null)
        {
            autoRefresh = true;
        }
    }

    protected void Load_ViewState()
    {
        //Before updating the charts, we know that this is a postback and that the viewstate shouldn't
        //be null, but check anyways, just to be sure
        if (ViewState["networksListVS"] != null)
        {
            networksInfo = (DataTable)ViewState["networksListVS"];
        }
        if (ViewState["HHmmVS"] != null)
        {
            HHmm = (String)ViewState["HHmmVS"];
        }
        if (ViewState["WindowVS"] != null)
        {
            Window = (String)ViewState["WindowVS"];
        }
        if (ViewState["ZoomFactorTopVS"] != null)
        {
            ZoomFactorTop = (String)ViewState["ZoomFactorTopVS"];
        }
        if (ViewState["ZoomFactorBottomVS"] != null)
        {
            ZoomFactorBottom = (String)ViewState["ZoomFactorBottomVS"];
        }
        if (ViewState["AutoRefresh"] != null)
        {
            autoRefresh = (Boolean)ViewState["AutoRefresh"];
        }
    }

---

希望对你有所帮助

是的，我以前也做过。不过，这不是最安全或最佳的做法。一旦我最终让viewstate工作起来，它就简单多了。

protected void Page_Load(object sender, EventArgs e)
{
    txtUser.Text = Request.Form[txtUser.UniqueID];
    dropCountry.SelectedValue = Request.Form[dropCountry.UniqueID];
    dropVisa.SelectedValue = Request.Form[dropVisa.UniqueID];
    dropEntry.SelectedValue = Request.Form[dropEntry.UniqueID];
    //Here I'm getting null value  
    basicdate.SelectedValue = Request.Form[basicdate.UniqueID];
}

public string TextVisaNumber
{
    get { return txtUser.Text; }
    set { txtUser.Text = value; }
}

public DateTime ExpiryDate
{
    get
    {
        return basicdate.SelectedDate;
    }
    set
    {
        basicdate.SelectedDate = value;
    }
}

<table>
<tr>
    <td>
        <asp:CheckBox ID="chkEnableMonthlyNotifications" runat ="server" CssClass="cell-Text" Text="Enable monthly notifications." />
        <br/>
    </td>
</tr>
<tr>
    <td>
        <label for="txtMonthStartDate">Specify start date for monthly notification</label>
        <br />
        <br />
        <asp:TextBox ID="txtMonthStartDate" runat="server" Enabled="true"></asp:TextBox>
        <asp:HiddenField ID="hdnMonthStartDate" runat="server" />
    </td>
</tr>
<tr>
    <td>
        <label for="txtMonthEndDate">Specify end date for monthly notification, or leave blank if no end date.</label>
        <br />
        <br />
        <asp:TextBox ID="txtMonthEndDate" runat="server" Enabled="true" > </asp:TextBox>
        <asp:HiddenField ID="hdnMonthEndDate" runat="server" />
    </td>
</tr>
</table>

$(document).ready(function ()
{
   $("[id$=_txtMonthStartDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnMonthStartDate]' });
   $("[id$=_txtMonthEndDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnMonthEndDate]' });
   $("[id$=_txtQuarterStartDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnQuarterStartDate]' });
   $("[id$=_txtQuarterEndDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnQuarterEndDate]' });
   $("[id$=_txtHalfYearStartDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnHalfYearStartDate]' });
   $("[id$=_txtHalfYearEndDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnHalfYearEndDate]' });
   $("[id$=_txtYearStartDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnYearStartDate]' });
   $("[id$=_txtYearEndDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnYearEndDate]' });
}

$(document).ready(function ()
{
  //Initializing the datepicker

  $("[id$=_txtMonthStartDate]").datepicker({ showOn: 'button', buttonImageOnly: true, buttonImage: '/icon_cal.png', altField: '[id$=_hdnMonthStartDate]' });

  //Code to set the datepicker's date again after post back
  if(!($("[id$=_txtMonthStartDate]").attr("Value") == undefined))
  {
    if($("[id$=_txtMonthStartDate]").attr("Value").length > 0)
    {
        $("[id$=_txtMonthStartDate]").datepicker("setDate",new Date($("[id$=_txtMonthStartDate]").val($("[id$=_txtMonthStartDate]").attr("Value"))));
    }
  }
}

    //Global ViewState Variables
    private DataTable networksInfo;
    private string HHmm;
    private string Window;
    private string ZoomFactorTop;
    private string ZoomFactorBottom;
    protected Boolean autoRefresh; 

    /// <summary>
    /// This page prerender allows me to save viewstate objects before anything bad
    /// happens. It's going to save any data that needs to persist across postbacks,
    /// since the page refreshes with an autorefresh. Whenever updated, the ViewState
    /// will also need to be updated.
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    void Page_PreRender(object sender, EventArgs e)
    {
        // Save the ViewStateObjects before the page is rendered.
        ViewState.Add("networksListVS", networksInfo);
        ViewState.Add("HHmmVS", HHmm);
        ViewState.Add("WindowVS", Window);
        ViewState.Add("ZoomFactorTopVS", ZoomFactorTop);
        ViewState.Add("ZoomFactorBottomVS", ZoomFactorBottom);
        ViewState.Add("AutoRefresh", autoRefresh);
    }

    protected void Create_ViewState(DateTime now)
    {
        //Populate Dropdown handles the initial value for networksInfo, but none of the others are

        //Set ViewState Vars' initial values
        if (ViewState["HHmmVS"] == null)
        {
            int HH = now.Hour;
            int mm = now.Minute;

            Change_Time(HH, mm);

        }
        if (ViewState["WindowVS"] == null)
        {
            //The default time window to view is 6 hours
            Window = "6";
        }
        if (ViewState["ZoomFactorTopVS"] == null)
        {
            //The default zoom factor is Window + 0
            ZoomFactorTop = "0";
        }
        if (ViewState["ZoomFactorBottomVS"] == null)
        {
            //The default zoom factor is Window + 0
            ZoomFactorBottom = "0";
        }
        if(ViewState["AutoRefresh"] == null)
        {
            autoRefresh = true;
        }
    }

    protected void Load_ViewState()
    {
        //Before updating the charts, we know that this is a postback and that the viewstate shouldn't
        //be null, but check anyways, just to be sure
        if (ViewState["networksListVS"] != null)
        {
            networksInfo = (DataTable)ViewState["networksListVS"];
        }
        if (ViewState["HHmmVS"] != null)
        {
            HHmm = (String)ViewState["HHmmVS"];
        }
        if (ViewState["WindowVS"] != null)
        {
            Window = (String)ViewState["WindowVS"];
        }
        if (ViewState["ZoomFactorTopVS"] != null)
        {
            ZoomFactorTop = (String)ViewState["ZoomFactorTopVS"];
        }
        if (ViewState["ZoomFactorBottomVS"] != null)
        {
            ZoomFactorBottom = (String)ViewState["ZoomFactorBottomVS"];
        }
        if (ViewState["AutoRefresh"] != null)
        {
            autoRefresh = (Boolean)ViewState["AutoRefresh"];
        }
    }

                ZoomFactorTop = "0";
                ZoomFactorBottom = "0";

                //Save the changes just made to the objects the ViewState needs access to
                SaveViewState();