How to use SharePoint RichTextBox within a Visual webPart

Ascx

<%@ Assembly Name="$SharePoint.Project.AssemblyFullName$" %> <%@ Assembly Name="Microsoft.Web.CommandUI, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Register Tagprefix="asp" Namespace="System.Web.UI" Assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" %> <%@ Import Namespace="Microsoft.SharePoint" %> <%@ Register Tagprefix="WebPartPages" Namespace="Microsoft.SharePoint.WebPartPages" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Control Language="C#" AutoEventWireup="true" CodeBehind="SPRTBoxUserControl.ascx.cs" Inherits="SPRTBox.SPRTBox.SPRTBoxUserControl" %> <table> <tr> <td> <SharePoint:InputFormTextBox  runat="server" ID="rtTest" ValidationGroup="CreateCase" Rows="8" Columns="40" RichText="true" RichTextMode="Compatible" AllowHyperlink="true" TextMode="MultiLine" /> </td> </tr> <tr><td><asp:Button ID="btnSave" runat="server" Text="Save"         onclick="btnSave_Click" /></td></tr> </table>

Ascx.Cs

using System; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using Microsoft.SharePoint; using System.Security; namespace SPRTBox.SPRTBox {     public partial class SPRTBoxUserControl : UserControl     {         protected void Page_Load(object sender, EventArgs e)         {         }         protected void btnSave_Click(object sender, EventArgs e)         {             try             {                 SPSecurity.RunWithElevatedPrivileges(delegate()                 {                     SPListItemCollection myColl = SPContext.Current.Web.Lists["RT Test"].Items;                     SPListItem item = myColl.Add();                     item["Title"] = "New Record";                     item["Test"] = rtTest.Text;                     item.Update();                 });             }             catch (Exception Ex)             {                 Response.Write(Ex.ToString());             }         }     } }