HtmlTextWriter.FilterAttributes Method

Definition

Namespace:

System.Web.UI

Assembly:

System.Web.dll

Removes all the markup and style attributes on all properties of the page or Web server control.

C#

protected virtual void FilterAttributes();

Examples

The following code example shows how to use a custom class, derived from the HtmlTextWriter class, that overrides the FilterAttributes method. When called, the FilterAttributes override checks whether the text writer renders any <label> or <a> elements:

• If a <label> element is being rendered, the FilterAttributes method checks whether a style attribute is rendered on the element and, if not, creates a style attribute and sets it to color: blue.

• If an <a> element is being rendered, the FilterAttributes method determines whether an href attribute is included and, if not, adds an href to the URL http://www.cohowinery.com.

C#

// Override the FilterAttributes method to check whether 
// <label> and <anchor> elements contain specific attributes.      
protected override void FilterAttributes()
{
    // If the <label> element is rendered and a style
    // attribute is not defined, add a style attribute 
    // and set its value to blue.
    if (TagKey == HtmlTextWriterTag.Label)
    {
        if (!IsAttributeDefined(HtmlTextWriterAttribute.Style))
        {
            AddAttribute("style", EncodeAttributeValue("color:blue", true));
            Write(NewLine);
            Indent = 3;
            OutputTabs();
        }
    }

    // If an <anchor> element is rendered and an href
    // attribute has not been defined, call the AddAttribute
    // method to add an href attribute
    // and set it to http://www.cohowinery.com.
    // Use the EncodeUrl method to convert any spaces to %20.
    if (TagKey == HtmlTextWriterTag.A)
    {
        if (!IsAttributeDefined(HtmlTextWriterAttribute.Href))
        {
            AddAttribute("href", EncodeUrl("http://www.cohowinery.com"));
        }
    }
    // Call the FilterAttributes method of the base class.
    base.FilterAttributes();
}

Remarks

Before attributes are rendered on a markup element, the FilterAttributes method is called. In turn, the FilterAttributes method calls the OnAttributeRender and OnStyleAttributeRender methods for each attribute and style to render.

Applies to

See also

• TextWriter
• OnAttributeRender(String, String, HtmlTextWriterAttribute)
• OnStyleAttributeRender(String, String, HtmlTextWriterStyle)