GridView with Edit Form (Template)

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections.Specialized;

namespace TemplateGridView
{
    public class TemplateGridView : GridView
    {
        #region EditItemTemplate

        private IBindableTemplate _EditItemTemplate;

        private bool _EnableTemplateEditing;

        public bool EnableTemplateEditing
        {
            get { return _EnableTemplateEditing; }
            set { _EnableTemplateEditing = value; }
        }

        [PersistenceMode(PersistenceMode.InnerProperty), TemplateContainer(typeof(GridViewRow), System.ComponentModel.BindingDirection.TwoWay)]
        public IBindableTemplate EditItemTemplate
        {
            set { _EditItemTemplate = value; }
            get { return _EditItemTemplate; }
        }

        protected override void ExtractRowValues(System.Collections.Specialized.IOrderedDictionary fieldValues, GridViewRow row, bool includeReadOnlyFields, bool includePrimaryKey)
        {
            if (_EnableTemplateEditing)
            {
                IOrderedDictionary dict = _EditItemTemplate.ExtractValues(row.Cells[0]);
                foreach (string s in dict.Keys)
                    fieldValues.Add(s, dict[s]);
            }
            else
                base.ExtractRowValues(fieldValues, row, includeReadOnlyFields, includePrimaryKey);
        }

        protected override void InitializeRow(GridViewRow row, DataControlField[] fields)
        {
            DataControlRowState state = row.RowState & DataControlRowState.Edit;
            if (row.RowType == DataControlRowType.DataRow && state != DataControlRowState.Normal && _EnableTemplateEditing == true)
            {
                int ColSpan = fields.Length;
                row.Cells.Clear();

                TableCell cell = new TableCell();
                cell.ColumnSpan = ColSpan;

                _EditItemTemplate.InstantiateIn(cell);
                row.Cells.Add(cell);
            }
            else
                base.InitializeRow(row, fields);
        }

        #endregion

        protected override void OnInit(EventArgs e)
        {
            if (_EnableTemplateEditing && _EditItemTemplate == null)
                throw new Exception("You have to enter EditItemTemplate to use TemplateEditing!");
            base.OnInit(e);
        }
    }
}