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HtmlTextWriter.IsAttributeDefined Method

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Definition

Namespace:
System.Web.UI
Assembly:
System.Web.dll

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

Overloads

IsAttributeDefined(HtmlTextWriterAttribute)

Determines whether the specified markup attribute and its value are rendered during the next call to the RenderBeginTag method.
IsAttributeDefined(HtmlTextWriterAttribute, String)

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

IsAttributeDefined(HtmlTextWriterAttribute)

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

protected:
 bool IsAttributeDefined(System::Web::UI::HtmlTextWriterAttribute key);
protected bool IsAttributeDefined (System.Web.UI.HtmlTextWriterAttribute key);
member this.IsAttributeDefined : System.Web.UI.HtmlTextWriterAttribute -> bool
Protected Function IsAttributeDefined (key As HtmlTextWriterAttribute) As Boolean

Parameters

key
HtmlTextWriterAttribute

The HtmlTextWriterAttribute associated with the markup attribute.

Returns

Boolean

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

Examples

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" );
   }
}

// 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");
    }
}

' 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 Then
    If Not IsAttributeDefined(HtmlTextWriterAttribute.Size) Then
        AddAttribute(GetAttributeKey("size"), "30pt")
    End If
End If

Remarks

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

See also

Applies to

IsAttributeDefined(HtmlTextWriterAttribute, String)

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

protected:
 bool IsAttributeDefined(System::Web::UI::HtmlTextWriterAttribute key, [Runtime::InteropServices::Out] System::String ^ % value);
protected bool IsAttributeDefined (System.Web.UI.HtmlTextWriterAttribute key, out string value);
member this.IsAttributeDefined : System.Web.UI.HtmlTextWriterAttribute * string -> bool
Protected Function IsAttributeDefined (key As HtmlTextWriterAttribute, ByRef value As String) As Boolean

Parameters

key
HtmlTextWriterAttribute

The HtmlTextWriterAttribute associated with the markup attribute.

value
String

The value assigned to the attribute.

Returns

Boolean

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

Remarks

If the IsAttributeDefined method returns true, the value to be assigned to the HtmlTextWriterAttribute object is returned in the value parameter.

See also

Applies to