[DefaultValueAttribute(RenderModeEnum.Auto)]
public RenderModeEnum RenderMode { get; set; }

<DefaultValueAttribute(RenderModeEnum.Auto)> _
Public Property RenderMode As RenderModeEnum

Use this property to determine what type of rendering you want applied to your control. For example, each render type performs the following type of behavior: If the rendering mode is Auto, then the control renders using JSON(JavaScript Object Notation) mode, where the page updates the control in partial rendering mode. While in partial rendering mode, it renders using Html mode to prevent the page from flickering. If the rendering mode is JSON, the control renders as an empty control, where javascript is used to create all of its child elements on the client-side. If the rendering mode is Html, the control renders as a regular control where the HTML code of all its child elements render on the server-side.