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HtmlTextWriter.AddAttribute Method (HtmlTextWriterAttribute, String)

Adds the markup attribute and the attribute value to the opening tag of the element that the HtmlTextWriter object creates with a subsequent call to the RenderBeginTag method.

Namespace: System.Web.UI
Assembly: System.Web (in system.web.dll)

public virtual void AddAttribute (
	HtmlTextWriterAttribute key,
	string value
public void AddAttribute (
	HtmlTextWriterAttribute key, 
	String value
public function AddAttribute (
	key : HtmlTextWriterAttribute, 
	value : String
Not applicable.



An HtmlTextWriterAttribute that represents the markup attribute to add to the output stream.


A string containing the value to assign to the attribute.

Use the AddAttribute overload of the AddAttribute(HtmlTextWriterAttribute,String) method to render a standard markup attribute.

For an instance of any given markup element, the HtmlTextWriter class maintains a list of attributes for that element. When the RenderBeginTag method is called, any attributes that are added by the AddAttribute method are rendered to the opening tag of the element. The list of attributes is then cleared from the HtmlTextWriter.

The coding pattern for rendering markup elements is as follows:

  • Use the AddAttribute method to add any attributes to the element.

  • Use the RenderBeginTag method.

  • Use other methods as needed to render the content found between the element's opening and closing tags.

  • Use the RenderEndTag method.

The following code example shows how to use the AddAttribute overload of the AddAttribute(HtmlTextWriterAttribute,String) method to add an Onclick attribute to a markup element, and then set its value to the following ECMAScript code:

writer.AddAttribute(HtmlTextWriterAttribute.Onclick, "alert('Hello');");

writer.AddAttribute(HtmlTextWriterAttribute.Onclick, "alert('Hello');");

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0