Upravit

Sdílet prostřednictvím

HtmlTextWriter.OnTagRender(String, HtmlTextWriterTag) Method

  • Reference

Definition

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

Determines whether the specified markup element will be rendered to the requesting page.

protected:
 virtual bool OnTagRender(System::String ^ name, System::Web::UI::HtmlTextWriterTag key);
protected virtual bool OnTagRender (string name, System.Web.UI.HtmlTextWriterTag key);
abstract member OnTagRender : string * System.Web.UI.HtmlTextWriterTag -> bool
override this.OnTagRender : string * System.Web.UI.HtmlTextWriterTag -> bool
Protected Overridable Function OnTagRender (name As String, key As HtmlTextWriterTag) As Boolean

Parameters

name
String

A string containing the name of the element to render.

key
HtmlTextWriterTag

The HtmlTextWriterTag associated with the element.

Returns

Boolean

Always true.

Examples

The following code example shows how to override the OnTagRender method. If a Font element is being rendered, the OnTagRender override uses the IsAttributeDefined method to determine whether a Size attribute is being rendered. If not, it uses the AddAttribute method to create a Size attribute and set its value to 20pt.

// If a <font> element is to be rendered, check whether it contains
// a size attribute. If it does not, add one and set its value to
// 20 points, then return true.
protected override bool OnTagRender(string name, HtmlTextWriterTag key)
{

    if (key == HtmlTextWriterTag.Font)
    {
        if (!(IsAttributeDefined(HtmlTextWriterAttribute.Size)))
        {
            AddAttribute(HtmlTextWriterAttribute.Size, "20pt");
            return true;
        }
    }

    // If the element is not a <font> element, use
    // the base functionality of the OnTagRenderMethod.
    return base.OnTagRender(name, key);
}

' If a <font> element is to be rendered, check whether it contains
' a size attribute. If it does not, add one and set its value to
' 20 points, then return true.
Protected Overrides Function OnTagRender( _
    name As String, _
    key As HtmlTextWriterTag) _
As Boolean

    If (key = HtmlTextWriterTag.Font) Then
        If Not (IsAttributeDefined(HtmlTextWriterAttribute.Size)) Then
            AddAttribute(HtmlTextWriterAttribute.Size, "20pt")
            Return True
        End If
    End If

    ' If the element is not a <font> element, use
    ' the base functionality of the OnTagRenderMethod.
    Return MyBase.OnTagRender(name, key)
End Function

Remarks

The HtmlTextWriter class implementation of the OnTagRender method always returns true. The OnTagRender overrides can determine whether an element will be rendered to the page.

Notes to Inheritors

If you inherit from the HtmlTextWriter class, you can override the OnTagRender(String, HtmlTextWriterTag) method to return false to prevent a markup element from being rendered at all or for a particular markup language. For example, if you do not want the object that is derived from HtmlTextWriter to render the <font> element, you can override the OnTagRender(String, HtmlTextWriterTag) method to return false when a page is requested that contains a <font> element.

Applies to

See also