Documentation for: ASP.NET Ajax Version 1.0

This documentation is for a previous version. For the current released version, see the ASP.NET Ajax documentation on MSDN.

 

 

 

 

 

 

 

Timer Class

Performs asynchronous or synchronous Web page postbacks at a defined interval.

Syntax

CSharp

[DefaultPropertyAttribute("Interval")]
[DesignerAttribute("System.Web.UI.Design.TimerDesigner, System.Web.Extensions.Design, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")]
[NonVisualControlAttribute]
[SupportsEventValidationAttribute]
[DefaultEventAttribute("Tick")]
[AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
[AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
public class Timer : Control, IPostBackEventHandler, IScriptControl

VisualBasic

<DefaultPropertyAttribute("Interval")> _
<DesignerAttribute("System.Web.UI.Design.TimerDesigner, System.Web.Extensions.Design, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")> _
<NonVisualControlAttribute> _
<SupportsEventValidationAttribute> _
<DefaultEventAttribute("Tick")> _
<AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
<AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
Public Class Timer _
	Inherits Control _
	Implements IPostBackEventHandler, IScriptControl

ManagedCPlusPlus

[DefaultPropertyAttribute(L"Interval")]
[DesignerAttribute(L"System.Web.UI.Design.TimerDesigner, System.Web.Extensions.Design, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")]
[NonVisualControlAttribute]
[SupportsEventValidationAttribute]
[DefaultEventAttribute(L"Tick")]
[AspNetHostingPermissionAttribute(SecurityAction::LinkDemand, Level = AspNetHostingPermissionLevel::Minimal)]
[AspNetHostingPermissionAttribute(SecurityAction::InheritanceDemand, Level = AspNetHostingPermissionLevel::Minimal)]
public ref class Timer : public Control, IPostBackEventHandler, IScriptControl

JSharp

/** @attribute DefaultPropertyAttribute("Interval") */
/** @attribute DesignerAttribute("System.Web.UI.Design.TimerDesigner, System.Web.Extensions.Design, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35") */
/** @attribute NonVisualControlAttribute */
/** @attribute SupportsEventValidationAttribute */
/** @attribute DefaultEventAttribute("Tick") */
/** @attribute AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal) */
/** @attribute AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal) */
public class Timer extends Control implements IPostBackEventHandler, IScriptControl

Members

IconMemberDescription
TimerNew()Initializes a new instance of the Timer class.
AdapterGets the browser-specific adapter for the control. (Inherited from Control.)
AddedControl(Control, Int32)Called after a child control is added to the Controls collection of the Control object. (Inherited from Control.)
AddParsedSubObject(Object)Notifies the server control that an element, either XML or HTML, was parsed, and adds the element to the server control's ControlCollection object. (Inherited from Control.)
ApplyStyleSheetSkin(Page)Applies the style properties defined in the page style sheet to the control. (Inherited from Control.)
AppRelativeTemplateSourceDirectoryGets or sets the application-relative virtual directory of the Page or UserControl object that contains this control. (Inherited from Control.)
BindingContainerGets the control that contains this control's data binding. (Inherited from Control.)
BuildProfileTree(String, Boolean)Gathers information about the server control and delivers it to the Trace property to be displayed when tracing is enabled for the page. (Inherited from Control.)
ChildControlsCreatedGets a value that indicates whether the server control's child controls have been created. (Inherited from Control.)
ClearChildControlState()Deletes the control-state information for the server control's child controls. (Inherited from Control.)
ClearChildState()Deletes the view-state and control-state information for all the server control's child controls. (Inherited from Control.)
ClearChildViewState()Deletes the view-state information for all the server control's child controls. (Inherited from Control.)
ClientIDGets the server control identifier generated by ASP.NET. (Inherited from Control.)
ClientIDSeparatorGets a character value representing the separator character used in the ClientID property. (Inherited from Control.)
ContextGets the HttpContext object associated with the server control for the current Web request. (Inherited from Control.)
ControlsGets a ControlCollection object that represents the child controls for a specified server control in the UI hierarchy. (Inherited from Control.)
CreateChildControls()Called by the ASP.NET page framework to notify server controls that use composition-based implementation to create any child controls they contain in preparation for posting back or rendering. (Inherited from Control.)
CreateControlCollection()Creates a new ControlCollection object to hold the child controls (both literal and server) of the server control. (Inherited from Control.)
DataBind()Binds a data source to the invoked server control and all its child controls. (Inherited from Control.)
DataBind(Boolean)Binds a data source to the invoked server control and all its child controls with an option to raise the DataBinding event. (Inherited from Control.)
DataBindChildren()Binds a data source to the server control's child controls. (Inherited from Control.)
DataBindingOccurs when the server control binds to a data source. (Inherited from Control.)
DesignModeGets a value indicating whether a control is being used on a design surface. (Inherited from Control.)
Dispose()Enables a server control to perform final clean up before it is released from memory. (Inherited from Control.)
DisposedOccurs when a server control is released from memory, which is the last stage of the server control lifecycle when an ASP.NET page is requested. (Inherited from Control.)
EnabledGets or sets a value that indicates whether the Timer control initiates a postback to the server after the number of milliseconds specified in the Interval property has elapsed.
EnableThemingGets or sets a value indicating whether themes apply to this control. (Inherited from Control.)
EnableViewStateGets or sets a value indicating whether the server control persists its view state, and the view state of any child controls it contains, to the requesting client. (Inherited from Control.)
EnsureChildControls()Determines whether the server control contains child controls. If it does not, it creates child controls. (Inherited from Control.)
EnsureID()Creates an identifier for controls that do not have an identifier assigned. (Inherited from Control.)
Equals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
EventsGets a list of event handler delegates for the control. This property is read-only. (Inherited from Control.)
Finalize()Allows an Object to attempt to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
FindControl(String)Searches the current naming container for a server control with the specified id parameter. (Inherited from Control.)
FindControl(String, Int32)Searches the current naming container for a server control with the specified id and an integer, specified in the pathOffset parameter, which aids in the search. You should not override this version of the method. (Inherited from Control.)
Focus()Sets input focus to a control. (Inherited from Control.)
GetDesignModeState()Gets design-time data for a control. (Inherited from Control.)
GetHashCode()Serves as a hash function for a particular type. (Inherited from Object.)
GetScriptDescriptors()Retrieves properties from a Timer object that are passed to the client component that implements timer logic in the browser.
GetScriptReferences()Retrieves the client script for the Timer control.
GetType()Gets the Type of the current instance. (Inherited from Object.)
HasChildViewStateGets a value indicating whether the current server control's child controls have any saved view-state settings. (Inherited from Control.)
HasControls()Determines if the server control contains any child controls. (Inherited from Control.)
HasEvents()Returns a value indicating whether events are registered for the control or any child controls. (Inherited from Control.)
IDGets or sets the programmatic identifier assigned to the server control. (Inherited from Control.)
IdSeparatorGets the character used to separate control identifiers. (Inherited from Control.)
InitOccurs when the server control is initialized, which is the first step in its lifecycle. (Inherited from Control.)
IntervalGets or sets the number of milliseconds to wait before initiating a postback.
IsChildControlStateClearedGets a value indicating whether controls contained within this control have control state. (Inherited from Control.)
IsLiteralContent()Determines if the server control holds only literal content. (Inherited from Control.)
IsTrackingViewStateGets a value that indicates whether the server control is saving changes to its view state. (Inherited from Control.)
IsViewStateEnabledGets a value indicating whether view state is enabled for this control. (Inherited from Control.)
LoadOccurs when the server control is loaded into the Page object. (Inherited from Control.)
LoadControlState(Object)Restores control-state information from a previous page request that was saved by the SaveControlState() method. (Inherited from Control.)
LoadViewState(Object)Restores view-state information from a previous page request that was saved by the SaveViewState() method. (Inherited from Control.)
LoadViewStateByIDGets a value indicating whether the control participates in loading its view state by ID instead of index. (Inherited from Control.)
MapPathSecure(String)Retrieves the physical path that a virtual path, either absolute or relative, maps to. (Inherited from Control.)
MemberwiseClone()Creates a shallow copy of the current Object. (Inherited from Object.)
NamingContainerGets a reference to the server control's naming container, which creates a unique namespace for differentiating between server controls with the same ID property value. (Inherited from Control.)
OnBubbleEvent(Object, EventArgs)Determines whether the event for the server control is passed up the page's UI server control hierarchy. (Inherited from Control.)
OnDataBinding(EventArgs)Raises the DataBinding event. (Inherited from Control.)
OnInit(EventArgs)Raises the Init event. (Inherited from Control.)
OnLoad(EventArgs)Raises the Load event. (Inherited from Control.)
OnPreRender(EventArgs)Raises the PreRender event of the Timer control. (Overrides Control.OnPreRender(EventArgs).)
OnTick(EventArgs)Raises the Tick event of the Timer control.
OnUnload(EventArgs)Raises the Unload event. (Inherited from Control.)
OpenFile(String)Gets a Stream used to read a file. (Inherited from Control.)
PageGets a reference to the Page instance that contains the server control. (Inherited from Control.)
ParentGets a reference to the server control's parent control in the page control hierarchy. (Inherited from Control.)
PreRenderOccurs after the Control object is loaded but prior to rendering. (Inherited from Control.)
RaiseBubbleEvent(Object, EventArgs)Assigns any sources of the event and its information to the control's parent. (Inherited from Control.)
RaisePostBackEvent(String)Enables a Timer control to raise the Tick event when a page is posted to the server.
RemovedControl(Control)Called after a child control is removed from the Controls collection of the Control object. (Inherited from Control.)
Render(HtmlTextWriter)Adds Timer control content to a HtmlTextWriter object, which writes the content to be rendered to the browser. (Overrides Control.Render(HtmlTextWriter).)
RenderChildren(HtmlTextWriter)Outputs the content of a server control's children to a provided HtmlTextWriter object, which writes the content to be rendered on the client. (Inherited from Control.)
RenderControl(HtmlTextWriter)Outputs server control content to a provided HtmlTextWriter object and stores tracing information about the control if tracing is enabled. (Inherited from Control.)
RenderControl(HtmlTextWriter, ControlAdapter)Outputs server control content to a provided HtmlTextWriter object using a provided ControlAdapter object. (Inherited from Control.)
ResolveAdapter()Gets the control adapter responsible for rendering the specified control. (Inherited from Control.)
ResolveClientUrl(String)Gets a URL that can be used by the browser. (Inherited from Control.)
ResolveUrl(String)Converts a URL into one that is usable on the requesting client. (Inherited from Control.)
SaveControlState()Saves any server control state changes that have occurred since the time the page was posted back to the server. (Inherited from Control.)
SaveViewState()Saves any server control view-state changes that have occurred since the time the page was posted back to the server. (Inherited from Control.)
SetDesignModeState(IDictionary)Sets design-time data for a control. (Inherited from Control.)
SetRenderMethodDelegate(RenderMethod)Assigns an event handler delegate to render the server control and its content into its parent control. (Inherited from Control.)
SiteGets information about the container that hosts the current control when rendered on a design surface. (Inherited from Control.)
SkinIDGets or sets the skin to apply to the control. (Inherited from Control.)
TemplateControlGets or sets a reference to the template that contains this control. (Inherited from Control.)
TemplateSourceDirectoryGets the virtual directory of the Page or UserControl that contains the current server control. (Inherited from Control.)
TickOccurs when the number of milliseconds specified in the Interval property has elapsed and the page is posted to the server.
ToString()Returns a String that represents the current Object. (Inherited from Object.)
TrackViewState()Causes tracking of view-state changes to the server control so they can be stored in the server control's StateBag object. This object is accessible through the ViewState property. (Inherited from Control.)
UniqueIDGets the unique, hierarchically qualified identifier for the server control. (Inherited from Control.)
UnloadOccurs when the server control is unloaded from memory. (Inherited from Control.)
ViewStateGets a dictionary of state information that allows you to save and restore the view state of a server control across multiple requests for the same page. (Inherited from Control.)
ViewStateIgnoresCaseGets a value that indicates whether the StateBag object is case-insensitive. (Inherited from Control.)
VisibleOverrides the Visible property of the Control class to prevent setting this value. (Overrides Control.Visible.)

Remarks

The Timer control enables you to perform postbacks at a specified interval. When you use the Timer control as a trigger for an UpdatePanel control, the UpdatePanel control is updated by using an asynchronous, partial-page update. You must include a ScriptManager object in your Web page to use the Timer control.

You use the Timer control to update an UpdatePanel control by either including the timer inside the UpdatePanel control, or by placing the timer outside the UpdatePanel control and setting the timer as a trigger.

You can also initiate a postback of a complete Web page by including the Timer control in the Web page and not setting it as a trigger for an UpdatePanel control.

You can run server code when the timer interval has elapsed by creating an event handler for the Tick event. In the event handler, you can include code that dynamically adjusts the behavior of the Timer control.

Set the Interval property to specify how often postbacks will occur. Set the Enabled property to turn the Timer on or off.

note

The accuracy of when the Timer control posts back to the Web server depends on the accuracy of the ECMAScript (JavaScript) window.setTimeout() function running in the browser.

The Interval property is defined in milliseconds. You must set the Interval property to a value that lets at least one asynchronous postback complete before the next postback is initiated. When the Timer control is outside an UpdatePanel control, the timer continues to run while the content of the UpdatePanel control is refreshed. If a new postback is initiated while an earlier postback is being processed, the first postback will be canceled. The default value is 60,000 milliseconds (60 seconds).

note

Adding a Timer control with a small value in the Interval property can generate significant traffic to and from the Web server. Use the Timer control to refresh the content only as often as necessary.

Examples

The following example shows an UpdatePanel control that displays a randomly generated stock price and the time that the stock price was generated. The Timer control updates the content in the UpdatePanel control every 10 seconds.

note

In this example, the timer interval is set to 10 seconds so that when you run the example, you do not have to wait a long time to see the results. Because each timer interval results in a postback to the server that causes network traffic, in a production application you should set the interval to the longest time that is still practical for your application.

cs

<%@ Page Language="C#" AutoEventWireup="true" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Timer Example Page</title>
    <script runat="server">
        protected void Page_Load(object sender, EventArgs e)
        {
            OriginalTime.Text = DateTime.Now.ToLongTimeString();
        }

        protected void Timer1_Tick(object sender, EventArgs e)
        {
            StockPrice.Text = GetStockPrice();
            TimeOfPrice.Text = DateTime.Now.ToLongTimeString();
        }

        private string GetStockPrice()
        {
            double randomStockPrice = 50 + new Random().NextDouble();
            return randomStockPrice.ToString("C");
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server" />
        <asp:Timer ID="Timer1" OnTick="Timer1_Tick" runat="server" Interval="10000" />

        <asp:UpdatePanel ID="StockPricePanel" runat="server" UpdateMode="Conditional">
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="Timer1" />
        </Triggers>
        <ContentTemplate>
            Stock price is <asp:Label id="StockPrice" runat="server"></asp:Label><BR />
            as of <asp:Label id="TimeOfPrice" runat="server"></asp:Label>  
        </ContentTemplate>
        </asp:UpdatePanel>
        <div>
        Page originally created at <asp:Label ID="OriginalTime" runat="server"></asp:Label>
        </div>
    </form>
</body>
</html>

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 runat="server">
    <title>Timer Example Page</title>
    <script runat="server">
        Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
            OriginalTime.Text = DateTime.Now.ToLongTimeString()
        End Sub

        Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs)
            StockPrice.Text = GetStockPrice()
            TimeOfPrice.Text = DateTime.Now.ToLongTimeString()
        End Sub

        Private Function GetStockPrice() As String
            Dim randomStockPrice As Double = 50 + New Random().NextDouble()
            Return randomStockPrice.ToString("C")
        End Function

    </script>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server" />
        <asp:Timer ID="Timer1" OnTick="Timer1_Tick" runat="server" Interval="10000" />

        <asp:UpdatePanel ID="StockPricePanel" runat="server" UpdateMode="Conditional">
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="Timer1" />
        </Triggers>
        <ContentTemplate>
            Stock price is <asp:Label id="StockPrice" runat="server"></asp:Label><BR />
            as of <asp:Label id="TimeOfPrice" runat="server"></asp:Label>  
        </ContentTemplate>
        </asp:UpdatePanel>
        <div>
        Page originally created at <asp:Label ID="OriginalTime" runat="server"></asp:Label>
        </div>
    </form>
</body>
</html>

Permissions

  • AspNetHostingPermission

    for operating in a hosted environment. Demand value: LinkDemand. Permission value: Minimal.

  • AspNetHostingPermission

    for operating in a hosted environment. Demand value: InheritanceDemand. Permission value: Minimal.

Inheritance Hierarchy

Assembly: System.Web.Extensions (Module: System.Web.Extensions)