C# – How to extend the OOTB Content Editor Web Part in Sharepoint 2010

I need a webpart that has a plaintext field for a title, an image for a thumbnail and a HTML content-editable block, so I thought the best way to do this would be to try and extend the existing Content Editor Web Part. Unfortunately, the CEWP is marked as sealed so I can't subclass it. I've reflected and tried to recreate the functionality in my own custom webpart (see the end of the question for code), but the content of my custom version of the CEWP is not persisted.

Does anyone know how I can:

• safely subclass the ContentEditableWebPart, or
• include a rich text block (including the RTE Ribbon) in a custom web part, or
• host multiple web parts in one "wrapper" web part?

Thanks in advance!

code follows below (stuff that was stopping it compiling that was copied from reflector has been commented out/altered/removed)

using System;
using System.ComponentModel;
using System.Security.Permissions;
using System.Web;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml;
using System.Xml.Serialization;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Security;
using Microsoft.SharePoint.Utilities;
using Microsoft.SharePoint.WebControls;
using Microsoft.SharePoint.WebPartPages;

namespace Public.Webparts
{
    [ToolboxItemAttribute(false)]
    [XmlRoot(Namespace="Webparts/ProductItem")]
    public class ProductItemWebPart :System.Web.UI.WebControls.WebParts.WebPart
    {


     // Fields
    private string _content;
    private bool _contentHasToken;
    private string _contentLink;
    private string _partContent;
    private string _partStorage;
    private HtmlGenericControl editableRegion = new HtmlGenericControl();
    private HtmlGenericControl emptyPanel = new HtmlGenericControl();
    private const string EmptyPanelHtmlV4 = "<A href=\"#\" title=\"{0}\" style=\"padding:8px 0px\" class=\"ms-toolbar ms-selectorlink\" >{0}</A>";
    internal const string InputContentClientId = "content";

    // Methods
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    public ProductItemWebPart()
    {
        //base.PreRender += new EventHandler(this.OnPreRender);
        if (this.Title.Length == 0)
        {
            this.Title = "Product Item Webpart";
        }
        if (this.Description.Length == 0)
        {
            this.Description = "This web part contains a title, content and image for a product item.";
        }
    }

    private string GetContent()
    {

        if (this._partContent != null)
        {
            return SPHttpUtility.NoEncode(ReplaceTokens(this._partContent));
        }
        return "";
    }

    protected internal string ReplaceTokens(string input)
    {
        string str = string.Empty;
        if (this.WebPartManager != null)
        {
            return SPWebPartManager.ReplaceTokens(HttpContext.Current, SPContext.Current.Web, this, input);
        }
        if (input != null)
        {
            str = input;
        }
        return str;
    }


    private string getEmptyPanelHtml()
    {
        return "<A href=\"#\" title=\"Click to enter content.\" style=\"padding:8px 0px\" class=\"ms-toolbar ms-selectorlink\" >Click to enter content.</A>";
    }



    //private void HttpAsyncCallback(object state)
    //{
    //    ULS.SendTraceTag(0x38393969, ULSCat.msoulscat_WSS_WebParts, ULSTraceLevel.Medium, "ASYNC: Http Callback: UniqueID={0}", new object[] { this.UniqueID.ToString() });
    //    if ((HttpStatusCode.OK != base.GetHttpWebResponse(this._contentLink, out this._partContent)) && (this._content == null))
    //    {
    //        this._partContent = "<p class=\"UserGeneric\">" + SPHttpUtility.HtmlEncode(WebPartPageResource.GetString("CannotRetrieveContent", new object[] { WebPartPageResource.GetString("ContentLinkLiteral") })) + "</p>";
    //    }
    //}

    private bool inEditMode()
    {
        SPWebPartManager currentWebPartManager = (SPWebPartManager) WebPartManager.GetCurrentWebPartManager(this.Page);
        return (((currentWebPartManager != null) && !base.IsStandalone) && currentWebPartManager.GetDisplayMode().AllowPageDesign);
    }

    //[SharePointPermission(SecurityAction.Demand, ObjectModel=true)]
    //public override string LoadResource(string id)
    //{
    //    string str = WebPartPageResource.GetString(id);
    //    if (str != null)
    //    {
    //        return str;
    //    }
    //    return id;
    //}

    [SharePointPermission(SecurityAction.Demand, ObjectModel=true)]
    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);
        if (this.ShowContentEditable())
        {
            SPRibbon current = SPRibbon.GetCurrent(this.Page);
            if (current != null)
            {
                current.MakeTabAvailable("Ribbon.EditingTools.CPEditTab");
                current.MakeTabAvailable("Ribbon.Image.Image");
                current.MakeTabAvailable("Ribbon.EditingTools.CPInsert");
                current.MakeTabAvailable("Ribbon.Link.Link");
                current.MakeTabAvailable("Ribbon.Table.Layout");
                current.MakeTabAvailable("Ribbon.Table.Design");
                //if (!(this.Page is WikiEditPage))
                //{
                //    current.TrimRTEWikiControls();
                //}
            }
        }
    }

    [SharePointPermission(SecurityAction.Demand, ObjectModel=true)]
    protected override void OnLoad(EventArgs e)
    {
        this.Controls.Add(this.editableRegion);
        this.Controls.Add(this.emptyPanel);
        this.editableRegion.Visible = false;
        this.emptyPanel.Visible = false;
        base.OnLoad(e);
        string str = this.Page.Request.Form[this.ClientID + "content"];
        if ((str != null) && (this._content != str))
        {
            this._content = str;
            try
            {
                SPWebPartManager currentWebPartManager = (SPWebPartManager) WebPartManager.GetCurrentWebPartManager(this.Page);
                Guid storageKey = currentWebPartManager.GetStorageKey(this);
                currentWebPartManager.SaveChanges(storageKey);
            }
            catch (Exception exception)
            {
                Label child = new Label();
                child.Text = exception.Message;
                this.Controls.Add(child);
            }
        }
        if (this.ShowContentEditable())
        {
            string str2;
            //if (this.ContentHasToken)
            //{
            //    str2 = ReplaceTokens(this._content);
            //}
            //else
            //{
            //    str2 = this._content;
            //}

            str2 = this._content;

            this.Page.ClientScript.RegisterHiddenField(this.ClientID + "content", str2);
            this.editableRegion.Visible = true;
            this.emptyPanel.Visible = true;
            this.emptyPanel.TagName = "DIV";
            this.emptyPanel.Style.Add(HtmlTextWriterStyle.Cursor, "hand");
            this.emptyPanel.Controls.Add(new LiteralControl(this.getEmptyPanelHtml()));
            this.emptyPanel.Style.Add(HtmlTextWriterStyle.TextAlign, "center");
            base.Attributes["RteRedirect"] = this.editableRegion.ClientID;
            ScriptLink.RegisterScriptAfterUI(this.Page, "SP.UI.Rte.js", false);
            ScriptLink.RegisterScriptAfterUI(this.Page, "SP.js", false);
            ScriptLink.RegisterScriptAfterUI(this.Page, "SP.Runtime.js", false);
            this.editableRegion.TagName = "DIV";
            this.editableRegion.InnerHtml = str2;
            this.editableRegion.Attributes["class"] = "ms-rtestate-write ms-rtestate-field";
            this.editableRegion.Attributes["contentEditable"] = "true";
            this.editableRegion.Attributes["InputFieldId"] = this.ClientID + "content";
            this.editableRegion.Attributes["EmptyPanelId"] = this.emptyPanel.ClientID;
            this.editableRegion.Attributes["ContentEditor"] = "True";
            this.editableRegion.Attributes["AllowScripts"] = "True";
            this.editableRegion.Attributes["AllowWebParts"] = "False";
            string script = "RTE.RichTextEditor.transferContentsToInputField('" + SPHttpUtility.EcmaScriptStringLiteralEncode(this.editableRegion.ClientID) + "');";
            this.Page.ClientScript.RegisterOnSubmitStatement(base.GetType(), "transfer" + this.editableRegion.ClientID, script);
            if (string.IsNullOrEmpty(this._content))
            {
                this.emptyPanel.Style["display"] = "";
                this.editableRegion.Style["display"] = "none";
            }
            else
            {
                this.emptyPanel.Style["display"] = "none";
                this.editableRegion.Style["display"] = "";
            }
        }
    }

    //private void OnPreRender(object sender, EventArgs e)
    //{
    //    Uri fullURLPath = base.GetFullURLPath(this._contentLink);
    //    if ((fullURLPath != null) && !base.TryToGetFileFromDatabase(fullURLPath, out this._partContent))
    //    {
    //        ULS.SendTraceTag(0x38393968, ULSCat.msoulscat_WSS_WebParts, ULSTraceLevel.Medium, "ASYNC: Begin Fetch: UniqueID={0}", new object[] { this.UniqueID.ToString() });
    //        base.RegisterWorkItemCallback(new WaitCallback(this.HttpAsyncCallback), null);
    //    }
    //}

    [SharePointPermission(SecurityAction.Demand, ObjectModel=true)]
    //protected override void RenderWebPart(HtmlTextWriter writer)
    protected override void Render(HtmlTextWriter writer)
    {
        //if (this.ShowContentEditable() && base.WebPartManager.IsAllowedToScript(this))
        if (this.ShowContentEditable())
        {
            base.Render(writer);
        }
        else
        {
            writer.Write(this.GetContent());
        }
    }

    //[SharePointPermission(SecurityAction.Demand, ObjectModel=true)]
    //protected internal override bool RequiresWebPartClientScript()
    //{
    //    return true;
    //}

    //public bool ShouldSerializeContent()
    //{
    //    if (!base.SerializeAll)
    //    {
    //        return (this.WebPartDefault._content != this._content);
    //    }
    //    return true;
    //}

    //public bool ShouldSerializeContentHasToken()
    //{
    //    return ((this.WebPartDefault._contentHasToken != this._contentHasToken) && !base.SerializeAll);
    //}

    //public bool ShouldSerializeContentLink()
    //{
    //    if (!base.SerializeAll)
    //    {
    //        return (this.WebPartDefault._contentLink != this._contentLink);
    //    }
    //    return true;
    //}

    public bool ShouldSerializePartStorage()
    {
        //if (!base.SerializeAll)
        //{
            //return (this.WebPartDefault._partStorage != this._partStorage);
        //}
        return true;
    }

    internal bool ShowContentEditable()
    {
        return (((SPContext.Current.Web.UIVersion > 3) && (this._partContent == null)) && this.inEditMode());
    }


    //[XmlElement("ContentHasToken", IsNullable=false), Browsable(false), WebPartStorage(Storage.Shared)]
    //public bool ContentHasToken
    //{
    //    get
    //    {
    //        return this._contentHasToken;
    //    }
    //    set
    //    {
    //        this._contentHasToken = value;
    //    }
    //}



    //private string EncodedInvalidContentError
    //{
    //    get
    //    {
    //        string str2;
    //        string str = "<a id=\"" + this.ID + "HelpLink\" href=\"javascript:HelpWindowUrl('" + SPHttpUtility.NoEncode("sts/html/dpvwpabt.htm") + "');\">" + SPHttpUtility.HtmlEncode(WebPartPageResource.GetString("InvalidContentErrorHelpLink")) + "</a>";
    //        if ((this.Context != null) && Utility.BrowserIsIE(this.Context.Request.Browser))
    //        {
    //            str2 = "InvalidContentError";
    //        }
    //        else
    //        {
    //            str2 = "InvalidContentErrorDL";
    //        }
    //        return ("<p><div class=\"UserGeneric\">" + string.Format(CultureInfo.InvariantCulture, SPHttpUtility.HtmlEncodeAllowSimpleTextFormatting(WebPartPageResource.GetString(str2)), new object[] { str }) + "</div></p>");
    //    }
    //}

    [Resources("PartStorageLiteral", "Advanced", "PartStorage"), WebPartStorage(Storage.Personal), XmlElement("PartStorage", IsNullable=false)]
    public string PartStorage
    {
        get
        {
            //return Utility.GetMemberString(this._partStorage);
            return this._partStorage ?? String.Empty;
        }
        set
        {           
            //Utility.SetMemberString(ref this._partStorage, value);

            if (value != null && value.Length > 0)
            {
                this._partStorage = value;
            }
            else
            {
                this._partStorage = null;
            }
        }
    }

    //internal ContentEditorWebPart WebPartDefault
    //{
    //    get
    //    {
    //        return (ContentEditorWebPart) base.WebPartDefault;
    //    }
    //}


    }
}