public string jQueryScriptPath
{
    get { return (string)ViewState["jQueryScriptPath"]; }
    set { ViewState["jQueryScriptPath"] = value; }
}

public string CollapseControlID
{
    get { return (string)ViewState["CollapseControlID"]; }
    set { ViewState["CollapseControlID"] = value; }
}
public string ExpandControlID
{
    get { return (string)ViewState["ExpandControlID"]; }
    set { ViewState["ExpandControlID"] = value; }
}
public string ImageControlID
{
    get { return (string)ViewState["ImageControlID"]; }
    set { ViewState["ImageControlID"] = value; }
}
public string ExpandedImage
{
    get { return (string)ViewState["ExpandedImage"]; }
    set { ViewState["ExpandedImage"] = value; }
}
public string CollapsedImage
{
    get { return (string)ViewState["CollapsedImage"]; }
    set { ViewState["CollapsedImage"] = value; }
}        
public bool Collapsed
{
    get { return (bool)(ViewState["Collapsed"] ?? false); }
    set { ViewState["Collapsed"] = value; }
}
public bool SuppressPostBack
{
    get { return (bool)(ViewState["SuppressPostBack"] ?? false); }
    set { ViewState["SuppressPostBack"] = value; }
}

public string OnExpand
{
    get { return (string)(ViewState["OnExpand"] ?? string.Empty); }
    set { ViewState["OnExpand"] = value; }
}
public string OnExpanded
{
    get { return (string)ViewState["OnExpanded"] ?? string.Empty; }
    set { ViewState["OnExpanded"] = value; }
}        
public string OnExpandComplete
{
    get { return (string)ViewState["OnExpandComplete"] ?? string.Empty; }
    set { ViewState["OnExpandComplete"] = value; }
}
public string OnCollapse
{
    get { return (string)ViewState["OnCollapse"] ?? string.Empty; }
    set { ViewState["OnCollapse"] = value; }
}
public string OnCollapsed
{
    get { return (string)ViewState["OnCollapsed"] ?? string.Empty; }
    set { ViewState["OnCollapsed"] = value; }
}
public string OnCollapseComplete
{
    get { return (string)ViewState["OnCollapseComplete"] ?? string.Empty; }
    set { ViewState["OnCollapseComplete"] = value; }
}

protected override void OnInit(EventArgs e)
{
    //Create Client State Hidden Field and add to Controls collection
    CreateClientStateField();
    Page.PreLoad += Page_PreLoad;
    base.OnInit(e);
}
protected override void OnLoad(EventArgs e)
{
    if (!_loadedClientStateValues)
    {
        LoadClientStateValues();
    }
    base.OnLoad(e);
}
protected override void OnPreRender(EventArgs e)
{
    //Must Call base class OnPreRender
    base.OnPreRender(e);
    //Saves Client State
    SaveClientStateValues();
}
protected override void Render(HtmlTextWriter writer)
{
    // Use ASP.NET's mechanism for ensuring Controls are within a form
    // (since unexpected behavior can occur when ExtenderControls are not)
    if (null != Page)
    {
        Page.VerifyRenderingInServerForm(this);
    }
    base.Render(writer);
}
private void Page_PreLoad(object sender, EventArgs e)
{
    // Needs to happen sometime after ASP.NET populates the control
    // values from the postback but sometime before Load so that
    // the values will be available to controls then. PreLoad is
    // therefore the obvious choice.
    LoadClientStateValues();
}        
/// <summary>
/// Creates or form ClientStateFiledID
/// </summary>
/// <returns>Client State Field Control ID</returns>
private string GetClientStateFieldID()
{
    return string.Format(System.Globalization.CultureInfo.InvariantCulture, "{0}_ClientState", ID);
}
/// <summary>
/// Creates HiddenField that is used to main client state
/// </summary>
/// <returns>ASP.NET HiddenField instance</returns>
private HiddenField CreateClientStateField()
{
    // add a hidden field so we'll pick up the value
    //
    HiddenField field = new HiddenField();
    field.ID = GetClientStateFieldID();
    Controls.Add(field);
    ClientStateFieldID = field.ID;
    field.Value = this.Collapsed.ToString().ToLower();
    return field;
}
/// <summary>
/// Loads client state and store it on ClientState Property.
/// It also fires ClientStateValuesLoaded if an event handler attached
/// </summary>
private void LoadClientStateValues()
{
    if (!string.IsNullOrEmpty(ClientStateFieldID))
    {
        HiddenField hiddenField = (HiddenField)NamingContainer.FindControl(ClientStateFieldID);

        if ((hiddenField != null) && !string.IsNullOrEmpty(hiddenField.Value))
        {
            ClientState = bool.Parse(hiddenField.Value);
        }
    }

    if (null != ClientStateValuesLoaded)
    {
        ClientStateValuesLoaded(this, EventArgs.Empty);
    }

    _loadedClientStateValues = true;
}
/// <summary>
/// Saves Client State value into the HiddenField (ClientState Field)
/// </summary>
private void SaveClientStateValues()
{
    HiddenField hiddenField = null;

    // if we don't have a value here, this properties
    // object may have been created dynamically in code
    // so we create the field on demand.
    if (string.IsNullOrEmpty(ClientStateFieldID))
    {
        hiddenField = CreateClientStateField();
    }
    else
    {
        hiddenField = (HiddenField)NamingContainer.FindControl(ClientStateFieldID);
    }

    if (hiddenField != null)
    {
        hiddenField.Value = ClientState.ToString().ToLower();
    }
}

[Browsable(false)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public bool ClientState
{
    get
    {
        return _clientState;
    }
    set
    {
        _clientState = value;
    }
}

protected override IEnumerable<ScriptDescriptor>
        GetScriptDescriptors(System.Web.UI.Control targetControl)
{
    ScriptBehaviorDescriptor descriptor = new ScriptBehaviorDescriptor("jQueryASPNetAjaxControls.jQueryCollapsiblePanelExtender", targetControl.ClientID);

    descriptor.AddProperty("ClientStateFieldID", this.ClientStateFieldID);
    descriptor.AddProperty("CollapseControlID", this.CollapseControlID);
    descriptor.AddProperty("ExpandControlID", this.ExpandControlID);
    descriptor.AddProperty("ImageControlID", this.ImageControlID);
    descriptor.AddProperty("ExpandedImage", Page.ResolveClientUrl(this.ExpandedImage));
    descriptor.AddProperty("CollapsedImage", Page.ResolveClientUrl(this.CollapsedImage));
    descriptor.AddProperty("Collapsed", this.Collapsed);
    descriptor.AddProperty("SuppressPostBack", this.SuppressPostBack);
    if (!String.IsNullOrEmpty(this.OnExpand))
    {
        descriptor.AddEvent("expanding", this.OnExpand);
    }
    if (!String.IsNullOrEmpty(this.OnExpanded))
    {
        descriptor.AddEvent("expanded", this.OnExpanded);
    }
    if (!String.IsNullOrEmpty(this.OnExpandComplete))
    {
        descriptor.AddEvent("expandComplete", this.OnExpandComplete);
    }
    if (!String.IsNullOrEmpty(this.OnCollapse))
    {
        descriptor.AddEvent("collapsing", this.OnCollapse);
    }
    if (!String.IsNullOrEmpty(this.OnCollapsed))
    {
        descriptor.AddEvent("collapsed", this.OnCollapsed);
    }
    if (!String.IsNullOrEmpty(this.OnCollapseComplete))
    {
        descriptor.AddEvent("collapseComplete", this.OnCollapseComplete);
    }
    yield return descriptor;
}

protected override IEnumerable<ScriptReference>GetScriptReferences()
{
 string jqueryPath = jquery126Live;
 if (this.jQueryScriptPath != null)
 {
     jqueryPath = Page.ResolveClientUrl(this.jQueryScriptPath);
 }

 ScriptReference[] scripts = 
                   { new ScriptReference(jqueryPath), 
                     new ScriptReference("jQueryASPNetAjaxControls.jQueryCollapsiblePanelExtender.js", 
                     this.GetType().Assembly.FullName) };
    return scripts;
}

<cc1:jQueryCollapsiblePanelExtender ID="collapsiblePanelEx" 
    TargetControlID="childPanel"
    CollapseControlID="parentLink" 
    ExpandControlID="parentPanel" 
    ImageControlID="imgExpandCollapse"
    CollapsedImage="~/images/plus.png"
    ExpandedImage="~/images/minus.png" 
    Collapsed="false"
    OnCollapsed="collapsed" 
    OnExpanded="expanded" 
    runat="server"/>