protected override void CreateChildControls()
{
base.CreateChildControls();
Controls.Clear();
RockControlHelper.CreateChildControls( this, Controls );
_tbLowerValue = new NumberBox();
_tbLowerValue.ID = this.ID + "_lower";
_tbLowerValue.CssClass = "input-width-md js-number-range-lower";
Controls.Add( _tbLowerValue );
_tbUpperValue = new NumberBox();
_tbUpperValue.ID = this.ID + "_upper";
_tbUpperValue.CssClass = "input-width-md js-number-range-upper";
Controls.Add( _tbUpperValue );
}