如果你想要一个简单的面板，而不是重新发明轮子，你可以使用可折叠面板控件：
http://www.asp.net/AJAX/AjaxControlToolkit/Samples/CollapsiblePanel/CollapsiblePanel.aspx
可能是获得您所追求的功能的最简单方法？

哦，怎么会-我解决了这个问题：

public sealed class CollapsableArea : Control
{
    private const string ViewStateKeyCollapsableContentClientID = "collapsableContentClientID";

    private string CollapsableContentClientID
    {
        get
        {
            var obj = this.ViewState[ViewStateKeyCollapsableContentClientID];
            if (obj == null)
            {
                var collapsableContentClientID = Guid.NewGuid().ToString();
                this.ViewState[ViewStateKeyCollapsableContentClientID] = collapsableContentClientID;
                return collapsableContentClientID;
            }
            return (string)obj;
        }
    }

    /// <summary>
    /// Gets or sets the header text.
    /// </summary>
    /// <value>The header text.</value>
    public string HeaderText
    {
        get
        {
            this.EnsureChildControls();
            return this._collapseControl.Text;
        }
        set
        {
            this.EnsureChildControls();
            this._collapseControl.Text = value;
        }
    }

    public override ControlCollection Controls
    {
        get
        {
            // redirect controls
            return this._collapsableContent.Controls;
        }
    }

    #region child controls

    private readonly Panel _collapsableContent = new Panel();
    private readonly CollapsableControl _collapseControl = new CollapsableControl();

    #endregion

    public override Control FindControl(string id)
    {
        // need to redirect
        if (string.Equals(id, this._collapsableContent.ID))
        {
            return this._collapsableContent;
        }
        return this._collapsableContent.FindControl(id);
    }

    protected override void CreateChildControls()
    {
        base.Controls.Clear();

        var collapsableContentClientID = this.CollapsableContentClientID;
        this._collapsableContent.ID = collapsableContentClientID;
        this._collapseControl.AssociatedControlID = collapsableContentClientID;
        base.Controls.Add(this._collapseControl);
        base.Controls.Add(this._collapsableContent);
    }

    protected override void RenderChildren(HtmlTextWriter writer)
    {
        this._collapseControl.RenderControl(writer);
        // hack for code blocks
        if (!this.Controls.IsReadOnly)
        {
            this._collapsableContent.RenderControl(writer);
        }
        else
        {
            this._collapsableContent.RenderBeginTag(writer);
            base.RenderChildren(writer);
            this._collapsableContent.RenderEndTag(writer);
        }
    }
}

你的控件应该有一个Template控件属性来定义可折叠的内容。正如你所说的，还有一个AssociatedControlID属性来获取Label控件的id。

public class CollapsableArea : WebControl, INamingContainer
{
    public string AssociatedControlID { get; set; }
    public ITemplate ContentTemplate { get; set; }
}

您必须向页面的启动脚本注册一个jquery。

$("#The AssociatedControlID client control id").click(function(e) {
    $("#The CollapsableArea client control id").toggle();
}