ChtmlTextWriter Class

Compact HTML, or cHTML, is a subset of HTML 2.0, HTML 3.2, and HTML 4.0, and is designed to render on devices with limited memory and CPU power, along with small display screens, limited formatting capabilities, and a limited number of input options (such as a cell phone touch pad). Therefore, cHTML does not support the following:

• JPEG images.

• Tables.

• Image maps.

• Multiple character fonts and styles.

• Background colors and images.

• Frames.

• Style sheets.

The ChtmlTextWriter class derives from the Html32TextWriter class and much of its functionality is provided by the Html32TextWriter and the base class for all markup text writers, which is the HtmlTextWriter class.

The following code example demonstrates how to create a class named CustomChtmlTextWriter that is derived from the ChtmlTextWriter class. It creates two constructors and overrides the OnAttributeRender method to prevent the bgcolor style attribute from being written to the output stream of the ChtmlTextWriter object. It also creates a class named ChtmlCustomPageAdapter that defines one method, CreateCustomChtmlTextWriter, which creates and returns an instance of the CustomChtmlTextWriter class. The CustomChtmlTextWriter then renders cHTML content for a page to devices with browsers that use cHTML markup.

// Create a class that derives from the
// ChtmlTextWriter class.
using System;
using System.IO;
using System.Web.UI;
using System.Web.UI.WebControls.Adapters;

namespace AspNet.Samples.CS
{
	public class CustomChtmlTextWriter : ChtmlTextWriter
	{
		// Create two constructors for the new
		// text writer.
		public CustomChtmlTextWriter(TextWriter writer) : base(writer, DefaultTabString)
		{
		}

		public CustomChtmlTextWriter(TextWriter writer, String tabString)
			: base(writer, tabString)
		{
		}
		
		// Override the OnAttributeRender method to
		// not render the bgcolor attribute, which is
		// not supported in CHTML.
		protected override bool OnAttributeRender(string name, string value, HtmlTextWriterAttribute key)
		{
			if (String.Equals("bgcolor", name))
			{
				return false;
			}
			
			// Call the ChtmlTextWriter version of the
			// the OnAttributeRender method.
			return base.OnAttributeRender(name, value, key);
		}
	}

	// Derive from the WebControlAdapter class,
	// provide a CreateCustomChtmlTextWriter
	// method to attach to the custom writer.
	public class ChtmlCustomPageAdapter : WebControlAdapter
	{
		protected internal ChtmlTextWriter CreateCustomChtmlTextWriter(
			TextWriter writer)
		{
			return new CustomChtmlTextWriter(writer);
		}
	}
}

.NET Framework

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference