HiddenField Class

Reference

Definition

Namespace:: System.Web.UI.WebControls

Assembly:: System.Web.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Represents a hidden field used to store a non-displayed value.

public ref class HiddenField : System::Web::UI::Control, System::Web::UI::IPostBackDataHandler

[System.Web.UI.ControlValueProperty("Value")]
public class HiddenField : System.Web.UI.Control, System.Web.UI.IPostBackDataHandler

[<System.Web.UI.ControlValueProperty("Value")>]
type HiddenField = class
    inherit Control
    interface IPostBackDataHandler

Public Class HiddenField
Inherits Control
Implements IPostBackDataHandler

Inheritance: Object

Control
HiddenField

Attributes: ControlValuePropertyAttribute

Implements: IPostBackDataHandler

Examples

The following examples show how to use the HiddenField control to store the value of a TextBox control between posts to the server.

Important

The examples have a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.


<%@ Page language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
 
  void ValueHiddenField_ValueChanged (Object sender, EventArgs e)
  {
    
    // Display the value of the HiddenField control.
    Message.Text = "The value of the HiddenField control is " + ValueHiddenField.Value + ".";
    
  }
  
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head runat="server">
    <title>HiddenField Example</title>
</head>
<body>
        <form id="Form1" runat="server">
        
            <h3>HiddenField Example</h3>

            Please enter a value and click the submit button.<br/>
            
            <asp:Textbox id="ValueTextBox"
              runat="server"/>
              
            <br/>  
              
            <input type="submit" name="SubmitButton"
             value="Submit"
             onclick="PageLoad()" />
             
            <br/>
            
            <asp:label id="Message" runat="server"/>    
            
            <asp:hiddenfield id="ValueHiddenField"
              onvaluechanged="ValueHiddenField_ValueChanged"
              value="" 
              runat="server"/>
            
        </form>
    </body>
</html>

<script type="text/javascript">

  <!--
  function PageLoad()
  {
  
    // Set the value of the HiddenField control with the
    // value from the TextBox.
    Form1.ValueHiddenField.value = Form1.ValueTextBox.value;
    
  }
  -->
  
</script>


<%@ Page language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
 
  Sub ValueHiddenField_ValueChanged(ByVal sender As Object, ByVal e As EventArgs)
    
    ' Display the value of the HiddenField control.
    Message.Text = "The value of the HiddenField control is " & ValueHiddenField.Value & "."
    
  End Sub
  
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head runat="server">
    <title>HiddenField Example</title>
</head>
<body>
        <form id="Form1" runat="server">
        
            <h3>HiddenField Example</h3>

            Please enter a value and click the submit button.<br/>
            
            <asp:textbox id="ValueTextBox"
              runat="server"/>
              
            <br/>  
              
            <input type="submit" name="SubmitButton"
             value="Submit"
             onclick="PageLoad()" />
             
            <br/>
            
            <asp:label id="Message" runat="server"/>    
            
            <asp:hiddenfield id="ValueHiddenField"
              onvaluechanged="ValueHiddenField_ValueChanged"
              value="" 
              runat="server"/>
            
        </form>
    </body>
</html>

<script type="text/javascript">

  <!--
  function PageLoad()
  {
  
    // Set the value of the HiddenField control with the
    // value from the TextBox.
    Form1.ValueHiddenField.value = Form1.ValueTextBox.value;
    
  }
  -->
  
</script>

<asp:HiddenField id="HiddenField1" runat="server" value="1"/>

<asp:HiddenField id="HiddenField1" runat="server" value="1"/>

Remarks

In this topic:

Introduction
Declarative Syntax

Introduction

The HiddenField control is used to store a value that needs to be persisted across posts to the server. It is rendered as an <input type= "hidden"/> element.

Normally view state, session state, and cookies are used to maintain the state of a Web Forms page. However, if these methods are disabled or are not available, you can use the HiddenField control to store state values.

To specify the value for a HiddenField control, use the Value property. You can provide a routine that gets called every time the value of the HiddenField control changes between posts to the server by creating an event handler for the ValueChanged event.

Declarative Syntax

<asp:HiddenField
    EnableTheming="True|False"
    EnableViewState="True|False"
    ID="string"
    OnDataBinding="DataBinding event handler"
    OnDisposed="Disposed event handler"
    OnInit="Init event handler"
    OnLoad="Load event handler"
    OnPreRender="PreRender event handler"
    OnUnload="Unload event handler"
    OnValueChanged="ValueChanged event handler"
    runat="server"
    SkinID="string"
    Value="string"
    Visible="True|False"
/>

Constructors

HiddenField()

Initializes a new instance of the HiddenField class.

Properties

Adapter	Gets the browser-specific adapter for the control. (Inherited from Control)
AppRelativeTemplateSourceDirectory	Gets or sets the application-relative virtual directory of the Page or UserControl object that contains this control. (Inherited from Control)
BindingContainer	Gets the control that contains this control's data binding. (Inherited from Control)
ChildControlsCreated	Gets a value that indicates whether the server control's child controls have been created. (Inherited from Control)
ClientID	Gets the control ID for HTML markup that is generated by ASP.NET. (Inherited from Control)
ClientIDMode	Gets or sets the algorithm that is used to generate the value of the ClientID property. (Inherited from Control)
ClientIDSeparator	Gets a character value representing the separator character used in the ClientID property. (Inherited from Control)
Context	Gets the HttpContext object associated with the server control for the current Web request. (Inherited from Control)
Controls	Gets a ControlCollection object that represents the child controls for a specified server control in the UI hierarchy. (Inherited from Control)
DataItemContainer	Gets a reference to the naming container if the naming container implements IDataItemContainer. (Inherited from Control)
DataKeysContainer	Gets a reference to the naming container if the naming container implements IDataKeysControl. (Inherited from Control)
DesignMode	Gets a value indicating whether a control is being used on a design surface. (Inherited from Control)
EnableTheming	Gets or sets a value indicating whether themes apply to this control.
EnableViewState	Gets 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)
Events	Gets a list of event handler delegates for the control. This property is read-only. (Inherited from Control)
HasChildViewState	Gets a value indicating whether the current server control's child controls have any saved view-state settings. (Inherited from Control)
ID	Gets or sets the programmatic identifier assigned to the server control. (Inherited from Control)
IdSeparator	Gets the character used to separate control identifiers. (Inherited from Control)
IsChildControlStateCleared	Gets a value indicating whether controls contained within this control have control state. (Inherited from Control)
IsTrackingViewState	Gets a value that indicates whether the server control is saving changes to its view state. (Inherited from Control)
IsViewStateEnabled	Gets a value indicating whether view state is enabled for this control. (Inherited from Control)
LoadViewStateByID	Gets a value indicating whether the control participates in loading its view state by ID instead of index. (Inherited from Control)
NamingContainer	Gets 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)
Page	Gets a reference to the Page instance that contains the server control. (Inherited from Control)
Parent	Gets a reference to the server control's parent control in the page control hierarchy. (Inherited from Control)
RenderingCompatibility	Gets a value that specifies the ASP.NET version that rendered HTML will be compatible with. (Inherited from Control)
Site	Gets information about the container that hosts the current control when rendered on a design surface. (Inherited from Control)
SkinID	Gets or sets the skin to apply to the control.
TemplateControl	Gets or sets a reference to the template that contains this control. (Inherited from Control)
TemplateSourceDirectory	Gets the virtual directory of the Page or UserControl that contains the current server control. (Inherited from Control)
UniqueID	Gets the unique, hierarchically qualified identifier for the server control. (Inherited from Control)
ValidateRequestMode	Gets or sets a value that indicates whether the control checks client input from the browser for potentially dangerous values. (Inherited from Control)
Value	Gets or sets the value of the hidden field.
ViewState	Gets 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)
ViewStateIgnoresCase	Gets a value that indicates whether the StateBag object is case-insensitive. (Inherited from Control)
ViewStateMode	Gets or sets the view-state mode of this control. (Inherited from Control)
Visible	Gets or sets a value that indicates whether a server control is rendered as UI on the page. (Inherited from Control)

Methods

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)
BeginRenderTracing(TextWriter, Object)	Begins design-time tracing of rendering data. (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)
ClearCachedClientID()	Sets the cached ClientID value to `null`. (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)
ClearEffectiveClientIDMode()	Sets the ClientIDMode property of the current control instance and of any child controls to Inherit. (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 an EmptyControlCollection object used to indicate that child controls are not allowed.
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)
Dispose()	Enables a server control to perform final clean up before it is released from memory. (Inherited from Control)
EndRenderTracing(TextWriter, Object)	Ends design-time tracing of rendering data. (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)
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 FindControl method. (Inherited from Control)
FindControl(String)	Searches the current naming container for a server control with the specified `id` parameter. (Inherited from Control)
Focus()	Sets input focus to this control.
GetDesignModeState()	Gets design-time data for a control. (Inherited from Control)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetRouteUrl(Object)	Gets the URL that corresponds to a set of route parameters. (Inherited from Control)
GetRouteUrl(RouteValueDictionary)	Gets the URL that corresponds to a set of route parameters. (Inherited from Control)
GetRouteUrl(String, Object)	Gets the URL that corresponds to a set of route parameters and a route name. (Inherited from Control)
GetRouteUrl(String, RouteValueDictionary)	Gets the URL that corresponds to a set of route parameters and a route name. (Inherited from Control)
GetType()	Gets the Type of the current instance. (Inherited from Object)
GetUniqueIDRelativeTo(Control)	Returns the prefixed portion of the UniqueID property of the specified control. (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)
IsLiteralContent()	Determines if the server control holds only literal content. (Inherited from Control)
LoadControlState(Object)	Restores control-state information from a previous page request that was saved by the SaveControlState() method. (Inherited from Control)
LoadPostData(String, NameValueCollection)	Processes postback data for a HiddenField control.
LoadViewState(Object)	Restores view-state information from a previous page request that was saved by the SaveViewState() method. (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)
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.
OnUnload(EventArgs)	Raises the Unload event. (Inherited from Control)
OnValueChanged(EventArgs)	Raises the ValueChanged event.
OpenFile(String)	Gets a Stream used to read a file. (Inherited from Control)
RaiseBubbleEvent(Object, EventArgs)	Assigns any sources of the event and its information to the control's parent. (Inherited from Control)
RaisePostDataChangedEvent()	Notifies the ASP.NET application that the state of the HiddenField control has changed.
RemovedControl(Control)	Called after a child control is removed from the Controls collection of the Control object. (Inherited from Control)
Render(HtmlTextWriter)	Renders the Web server control content to the client's browser using the specified HtmlTextWriter object.
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, ControlAdapter)	Outputs server control content to a provided HtmlTextWriter object using a provided ControlAdapter object. (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)
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)
SetTraceData(Object, Object, Object)	Sets trace data for design-time tracing of rendering data, using the traced object, the trace data key, and the trace data value. (Inherited from Control)
SetTraceData(Object, Object)	Sets trace data for design-time tracing of rendering data, using the trace data key and the trace data value. (Inherited from Control)
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)

Events

DataBinding	Occurs when the server control binds to a data source. (Inherited from Control)
Disposed	Occurs 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)
Init	Occurs when the server control is initialized, which is the first step in its lifecycle. (Inherited from Control)
Load	Occurs when the server control is loaded into the Page object. (Inherited from Control)
PreRender	Occurs after the Control object is loaded but prior to rendering. (Inherited from Control)
Unload	Occurs when the server control is unloaded from memory. (Inherited from Control)
ValueChanged	Occurs when the value of the HiddenField control changes between posts to the server.

Explicit Interface Implementations

IControlBuilderAccessor.ControlBuilder	For a description of this member, see ControlBuilder. (Inherited from Control)
IControlDesignerAccessor.GetDesignModeState()	For a description of this member, see GetDesignModeState(). (Inherited from Control)
IControlDesignerAccessor.SetDesignModeState(IDictionary)	For a description of this member, see SetDesignModeState(IDictionary). (Inherited from Control)
IControlDesignerAccessor.SetOwnerControl(Control)	For a description of this member, see SetOwnerControl(Control). (Inherited from Control)
IControlDesignerAccessor.UserData	For a description of this member, see UserData. (Inherited from Control)
IDataBindingsAccessor.DataBindings	For a description of this member, see DataBindings. (Inherited from Control)
IDataBindingsAccessor.HasDataBindings	For a description of this member, see HasDataBindings. (Inherited from Control)
IExpressionsAccessor.Expressions	For a description of this member, see Expressions. (Inherited from Control)
IExpressionsAccessor.HasExpressions	For a description of this member, see HasExpressions. (Inherited from Control)
IParserAccessor.AddParsedSubObject(Object)	For a description of this member, see AddParsedSubObject(Object). (Inherited from Control)
IPostBackDataHandler.LoadPostData(String, NameValueCollection)	For a description of this member, see the LoadPostData(String, NameValueCollection) method.
IPostBackDataHandler.RaisePostDataChangedEvent()	For a description of this member, see the RaisePostDataChangedEvent() method.

Extension Methods

FindDataSourceControl(Control)	Returns the data source that is associated with the data control for the specified control.
FindFieldTemplate(Control, String)	Returns the field template for the specified column in the specified control's naming container.
FindMetaTable(Control)	Returns the metatable object for the containing data control.

Applies to

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