jQuery修改后的“隐藏字段值”发布回服务器后为空

Question

Summary: I have a web control that is dynamically added to the page. The control has a HiddenField child control. I am passing the control's ClientID to a jquery widget that is setting the value to a string (json converted to string). When the form is posted back to the server, the value of the HiddenField is a blank string. I value is in the Request.Form[ UniqueID ] object. The value is making it back to the server. The problem is that, I don't have access to the Request object when I need the value without modifying a lot of legacy code.

The strange thing is that the selectmany control is the one I am having a problem with, but it inherits from the SelectOne that is working properly. I think I am doing something wrong in the selectmany class because even if I try to push a value into the SelectOneHiddenValue it does not work ,but it works properly when the SelectOne uses it.

SelectOne:

[ToolboxData("<{0}:SelectOne runat=server></{0}:SelectOne>")]
public class SelectOne : Panel, IControl,ISelectOne
{
    #region structure

    private readonly Panel _selectOneTextboxContainer = new Panel();
    protected readonly TextBox SelectOneTextbox = new TextBox();
    protected readonly HiddenField SelectOneHiddenValue = new HiddenField();
    private readonly Panel _selectOneDropdownImageContainer = new Panel();
    private readonly Image _selectOneDropDownImage = new Image();

    #endregion

    private readonly IList<LookupItem> _selectedItems = new List<LookupItem>();

    #region properties
    public IList<LookupItem> SelectedItems { get { return _selectedItems; } }

    public bool MultiSelect { get; set; }
    public DisplayOption Display { get; set; }
    public string Name { get; set; }

    [DefaultValue(0)]
    public int LookupValueOrgID
    {
        get
        {
            EnsureChildControls();
            return Convert.ToInt32(String.IsNullOrEmpty(SelectOneHiddenValue.Value) ? "0" : SelectOneHiddenValue.Value);
        }

        set
        {
            EnsureChildControls();
            SelectOneHiddenValue.Value = value.ToString();
        }
    }

    [Bindable(true)]
    [Category("Appearance")]
    [DefaultValue("")]
    [Localizable(true)]
    public string Text
    {
        get
        {
            EnsureChildControls();
            return SelectOneTextbox.Text;
        }

        set
        {
            EnsureChildControls();
            SelectOneTextbox.Text = value;
        }
    }

    /// <summary>
    /// The minimum number of characters a user has to type before the autocompleter activates.
    /// </summary>
    [Bindable(true)]
    [Category("Appearance")]
    [DefaultValue(1)]
    [Localizable(true)]
    public int MinChars
    {
        get
        {
            int b = (ViewState["MinChars"] == null ? 1 : (int)ViewState["MinChars"]);
            return b;
        }
        set
        {
            ViewState["MinChars"] = value;
        }
    }

    /// <summary>
    /// The number of backend query results to store in cache. If set to 1 (the current result), no caching will happen. Must be >= 1.
    /// </summary>
    [Bindable(true)]
    [Category("Appearance")]
    [DefaultValue(10)]
    [Localizable(true)]
    public int CacheLength
    {
        get
        {
            int b = (ViewState["CacheLength"] == null ? 10 : (int)ViewState["CacheLength"]);
            return b;
        }
        set
        {
            ViewState["CacheLength"] = value;
        }
    }

    public string OuterMarkupClientID
    {
        get { return "SelectOne_Container" + ClientID; }
    }

    /// <summary>
    /// If true, target input text is appended to
    /// If false, target input text is replaced
    /// </summary>
    public bool AppendSelectedTextToInput { get; set; }

    public virtual string ContainerClass
    {
        get { return "SelectOneContainer"; }
    }

    #endregion

    #region constructor
    public SelectOne()
    {
        SetCssClasses();
    }

    #endregion
    #region lifecycle overrides

    protected override void CreateChildControls()
    {
        base.CreateChildControls();
        AddChildrenToControlCollection();
    }

    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);

        SetupClientEvents();
        ControlHelper.AddRequiredControl(this);

        var resourceName = string.Empty;

        var cs = Page.ClientScript;
        resourceName = "UI.Controls.resources.images.DropDownButton.gif";
        _selectOneDropDownImage.ImageUrl = cs.GetWebResourceUrl(GetType(), resourceName);

        SelectOneTextbox.Attributes.Add("lookupOrgID", LookupOrgID.ToString());
        SelectOneTextbox.Attributes.Add("cacheLength", CacheLength.ToString());
        SelectOneTextbox.Attributes.Add("service", Service);
        SelectOneTextbox.Attributes.Add("selectOneTextboxId", SelectOneTextbox.ClientID);
        SelectOneTextbox.Attributes.Add("selectOneHiddenValueId",SelectOneHiddenValue.ClientID);

    }

    #endregion

    #region private helpers
    private void SetCssClasses()
    {
        this.CssClass = ContainerClass + " AutocompleteContainer";
        _selectOneDropDownImage.CssClass = "SelectOneDropDownImage";
        SelectOneTextbox.CssClass = "SelectOneTextbox QuantifiTextBox";
        _selectOneTextboxContainer.CssClass = "SelectOneTextboxContainer";
        _selectOneDropdownImageContainer.CssClass = "SelectOneDropDownImageContainer";

    }

    private void SetupClientEvents()
    {
        ControlHelper.RegisterAutoCompleteScript(this);
        var resourceName = "UI.Controls.resources.scripts.SelectOne.js";

        string js;
        using (var sr = new StreamReader(GetType().Assembly.GetManifestResourceStream(resourceName)))
        {
            js = sr.ReadToEnd();
            sr.Close();
        }
        ClientScriptProxy.Current.RegisterStartupScript(this, typeof(SelectOne), "SelectOneJS", js, true);

        _selectOneDropDownImage.Attributes.Add("onclick", "SelectOne_ImageClick('" + SelectOneTextbox.ClientID + "');");
    }

    private void AddChildrenToControlCollection()
    {
        _selectOneTextboxContainer.Controls.Add(SelectOneTextbox);
        this.Controls.Add(_selectOneTextboxContainer);

        _selectOneDropdownImageContainer.Controls.Add(_selectOneDropDownImage);
        this.Controls.Add(_selectOneDropdownImageContainer);
        this.Controls.Add(SelectOneHiddenValue);
    }
    #endregion
}

Select Many:

[ToolboxData("<{0}:SelectMany runat=server></{0}:SelectMany>")]
public class SelectMany : SelectOne, ISelectMany
{
    #region structure

    private readonly Panel _selectedItemsPanel = new Panel();
    private readonly HiddenField _selectManyHiddenField = new HiddenField();

    public override string ContainerClass
    {
        get
        {
            return "SelectManyControlContainer";
        }
    }

    #endregion
    public SelectMany()
    {
        MultiSelect = true;
    }

    #region lifecycle overrides
    protected override void CreateChildControls()
    {
        base.CreateChildControls();


        _selectManyHiddenField.ID = "SelectedItemsHiddenValue";

        this.Controls.Add(_selectedItemsPanel);
        this.Controls.Add(_selectManyHiddenField);

        SelectOneTextbox.Attributes.Add("data-multiselect", MultiSelect.ToString());
    }

    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);
        var resourceName = "jquery.SelectedItemCollection.js";

        ClientScriptProxy.Current.RegisterClientScriptInclude(this, Page.ClientScript.GetWebResourceUrl(this.GetType(),resourceName));
        var serializer = new JavaScriptSerializer();
        var startupScript = String.Format("\n$('#{0}').each(function(){{" +
                                          "var selectedPlugin = $(this).SelectedItemCollection(" +
                                          "       {{" +
                                          "          itemData: {1}," +
                                          "          deleteImageUrl: '{2}'," +
                                          "          selectedTextId: '{3}', " +
                                          "          hiddenTextFieldId: '{4}' " +
                                          "       }});}});\n",
            this.ClientID, 
            serializer.Serialize(SelectedItems),
            GetDeleteImageUrl(),
            SelectOneTextbox.ClientID,
            _selectManyHiddenField.ClientID
            );
        ClientScriptProxy.Current.RegisterStartupScript(this,this.GetType(),"SelectedItemsJs_" + this.ClientID,startupScript,true);
    }
    #endregion

    #region public api
    public void BindForm()
    {
        EnsureChildControls();
        this.DataBind();
        var jsonString = _selectManyHiddenField.Value;

        SelectedItems.Clear();
        if (!jsonString.IsNullOrEmpty())
        {
            Json.Decode<IEnumerable<LookupItem>>(jsonString).ForEach(li => SelectedItems.Add(li));    
        }

    }
    #endregion

    private string GetDeleteImageUrl()
    {
        var cs = Page.ClientScript;
        const string resourceName = "UI.Controls.resources.images.close.gif";
        return cs.GetWebResourceUrl(this.GetType(), resourceName);
    }


}

Answer 1

Well, it was something stupid. And it took me forever to find. Basically, don't misuse the EnsureChildControls() method. The base class was calling that before some of it's properties were accessed. This called RecreateChildControls() after ViewState was restored, but before I could check the values.

To correct this, I added EnsureChildControls() in the OnInit override for both the base class and the derived class. That way, all my controls will be created properly and ViewState is restored after their creation.

    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);
        EnsureChildControls();
    }