Label.AddParsedSubObject(Object) Method

Reference

Definition

Namespace:: System.Web.UI.WebControls

Assembly:: System.Web.dll

Important

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Notifies the control that an element was parsed and adds the element to the Label control.

protected:
 override void AddParsedSubObject(System::Object ^ obj);

protected override void AddParsedSubObject (object obj);

override this.AddParsedSubObject : obj -> unit

Protected Overrides Sub AddParsedSubObject (obj As Object)

Parameters

obj: Object

An object that represents the parsed element.

Examples

The following code example demonstrates how to override the AddParsedSubObject method in a custom Label server control so that it always sets the text property to the parsed object's text property, if the parsed object is a Literal, and to an empty string otherwise.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %>
<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
        <title>Custom Label - AddParsedSubObject - C# Example</title>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom Label - AddParsedSubObject - C# Example</h3>
            
            <aspSample:CustomLabelAddParsedSubObject 
              id="Label1" runat="server" 
              ToolTip="Microsoft Corp.">Microsoft Corp.</aspSample:CustomLabelAddParsedSubObject>

        </form>
    </body>
</html>

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB.Controls" Assembly="Samples.AspNet.VB" %>
<%@ Page Language="VB" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
        <title>Custom Label - AddParsedSubObject - VB.NET Example</title>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom Label - AddParsedSubObject - VB.NET Example</h3>
            
            <aspSample:CustomLabelAddParsedSubObject id="Label1" runat="server" 
             ToolTip="Microsoft Corp.">Microsoft Corp.</aspSample:CustomLabelAddParsedSubObject>

        </form>
    </body>
</html>

using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
{
  [AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
  public sealed class CustomLabelAddParsedSubObject : System.Web.UI.WebControls.Label
  {
    protected override void AddParsedSubObject(object obj)
    {
      // If the server control contains any child controls.
      if (this.HasControls()) 
      {
        // Notify the base server control that an element, either XML or HTML, 
        // was parsed, and adds the element to the server control's 
        // ControlCollection object.
        base.AddParsedSubObject(obj);
      }
        // Else the server control doesn't contain any child controls.
      else 
      {
        // If the parsed element is a LiteralControl.
        if (obj is System.Web.UI.LiteralControl) 
        {
          // Set the server control's Text property to the parsed element's Text value.
          this.Text = ((System.Web.UI.LiteralControl)obj).Text;
        }
          // Else the parsed element is not a LiteralControl.
        else 
        {
          // If the server control has a value in the Text property.
          string currentText = this.Text;
          if (currentText.Length != 0) 
          {
            // Set the server control's Text property to an empty string.
            this.Text = System.String.Empty;

            // Notify the base server control that a new LiteralControl was parsed, 
            // and adds the element to the server control's ControlCollection object.
            base.AddParsedSubObject(new System.Web.UI.LiteralControl(currentText));
          }
          base.AddParsedSubObject(obj);
        }
      }
    }
  }
}

<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomLabelAddParsedSubObject
    Inherits System.Web.UI.WebControls.Label

    Protected Overrides Sub AddParsedSubObject(ByVal obj As Object)

        ' If the server control contains any child controls.
        If Me.HasControls() Then

            ' Notify the base server control that an element, either XML or HTML, 
            ' was parsed, and adds the element to the server control's 
            ' ControlCollection object.
            MyBase.AddParsedSubObject(obj)
            ' Else the server control doesn't contain any child controls.
        Else
            ' If the parsed element is a LiteralControl.
            If TypeOf obj Is System.Web.UI.LiteralControl Then

                ' Set the server control's Text property to the parsed element's Text value.
                Me.Text = CType(obj, System.Web.UI.LiteralControl).Text

                ' Else the parsed element is not a LiteralControl.
            Else
                ' If the server control has a value in the Text property.
                Dim currentText As String = Me.Text
                If currentText.Length <> 0 Then

                    ' Set the server control's Text property to an empty string.
                    Me.Text = System.String.Empty

                    ' Notify the base server control that a new LiteralControl was parsed, 
                    ' and adds the element to the server control's ControlCollection object.
                    MyBase.AddParsedSubObject(New System.Web.UI.LiteralControl(currentText))
                End If
                MyBase.AddParsedSubObject(obj)
            End If
        End If
    End Sub
End Class

Remarks

The AddParsedSubObject method is used primarily by control developers when deriving a custom control from the Label class.

If the input object is a LiteralControl, and the Label control has no child controls, the input object is used to set the Text property of the Label control. Otherwise, the AddParsedSubObject method of the base Control class is called and the specified object is added to the Controls collection.

Applies to

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