DataGRidView with DropDown style Combobox in Editmode

Question

hi

I have requirement to implement DropDown style combobox in DataGridView, Where i can Select value from Dropdown even can type new value. Here is the code that i have added for the same:

#region dgv_TETV_T_Display_EditingControlShowing
    private void dgv_TETV_T_Display_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
    {
        /// This event has been added to make Topics combo editable.
        /// 
        var cbo = e.Control as ComboBox;
        if (cbo == null) { return; }

        this.dgv_TETV_T_Display.NotifyCurrentCellDirty(false);

        cbo.DropDownStyle = ComboBoxStyle.DropDown;

        cbo.TextChanged -= new EventHandler(cbo_TextChanged);
        cbo.TextChanged += new EventHandler(cbo_TextChanged);

        cbo.Validating -= HandleComboBoxValidating;
        cbo.Validating += HandleComboBoxValidating;
    }
    #endregion

    #region cbo_TextChanged
    void cbo_TextChanged(object sender, EventArgs e)
    {
        this.dgv_TETV_T_Display.NotifyCurrentCellDirty(true);
    }
    #endregion

    #region HandleComboBoxValidating
    private void HandleComboBoxValidating(object sender, CancelEventArgs e)
    {
        var combo = sender as DataGridViewComboBoxEditingControl;
        string errorMessage = "";

        if (combo == null)
        { return; }

        if (combo.Text.Length > 0)
        {
            combo.Text = combo.Text.Trim();
        }

        if (!combo.Items.Contains(combo.Text)) //check if item is already in drop down, if not, add it to all           
        {
            var comboColumn = this.dgv_TETV_T_Display.Columns[this.dgv_TETV_T_Display.CurrentCell.ColumnIndex] as DataGridViewComboBoxColumn;

            if ((combo.Text != "") && (Validation.IsValidGroupName(combo.Text.ToString(), ref errorMessage) == true))
            {
                combo.Items.Add(combo.Text);
                comboColumn.Items.Add(combo.Text);
                this.dgv_TETV_T_Display.CurrentCell.Value = combo.Text;
            }
            else
            {
                this.dgv_TETV_T_Display.CurrentCell.Value = "";
            }
        }

        //else
        //{
        //    this.dgv_TETV_T_Display.CurrentCell.Value = combo.Text;
        //}
    }
    #endregion

With This code, whenever i type new value in comboboxcolumn, on cell validation new value gets added to dropdownlist. I want user to type new value and just want to display it , once user clicks on accept button , i want diaplyed item to add into Dropdown item list.

Please let me know, how i can achieve this.