protected override void CreateChildControls()
{
base.CreateChildControls();
Controls.Clear();
RockControlHelper.CreateChildControls( this, Controls );
_mfpMergeFields = new MergeFieldPicker();
_mfpMergeFields.ID = string.Format( "mfpMergeFields_{0}", this.ID );
_mfpMergeFields.SelectItem += MergeFields_SelectItem;
Controls.Add( _mfpMergeFields );
}