HtmlTextWriter::IsAttributeDefined Method (HtmlTextWriterAttribute)

 

Determines whether the specified markup attribute and its value are rendered during the next call to the RenderBeginTag method.

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

protected:
bool IsAttributeDefined(
	HtmlTextWriterAttribute key
)

Parameters

key
Type: System.Web.UI::HtmlTextWriterAttribute

The HtmlTextWriterAttribute associated with the markup attribute.

Return Value

Type: System::Boolean

true if the attribute is rendered during the next call to the RenderBeginTag method; otherwise, false.

To obtain the value to be assigned to the HtmlTextWriterAttribute object, use the IsAttributeDefined(HtmlTextWriterAttribute, String^%) overload instead of this one.

The following code example shows how to use an override of the RenderBeginTag method in a class that inherits from the HtmlTextWriter class. The RenderBeginTag override checks whether a <font> markup element will be rendered. If so, the override calls the IsAttributeDefined method to check whether the <font> element contains a Size attribute. If not, the AddAttribute method calls the GetAttributeKey method, which defines the Size attribute and sets its value to 30pt.

// If the tagKey parameter is set to a <font> element
// but a size attribute is not defined on the element,
// the AddStyleAttribute method adds a size attribute
// and sets it to 30 point.
if ( tagKey == HtmlTextWriterTag::Font )
{
   if (  !IsAttributeDefined( HtmlTextWriterAttribute::Size ) )
   {
      AddAttribute( GetAttributeKey( "size" ), "30pt" );
   }
}

.NET Framework
Available since 1.1
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