Main Page

  Previous Section Next Section


System.Web.UI (system.web.dll)class

The Control class defines properties, methods, and events that all server controls in ASP.NET require. ASP.NET controls do not inherit directly from this class; instead, they inherit from either the System.Web.UI.HtmlControls.HtmlControl or the System.Web.UI.WebControls.WebControl class, both of which inherit from the Control class. Similarly, the Page and UserControl classes inherit from TemplateControl, which inherits from this class.

The Control class contains many of the typical members you would expect in a control, including properties that reference the root of the control tree (Page) and a collection of contained controls (Controls). The EnableViewState property determines whether ASP.NET maintains the control's state automatically by using a hidden field. The ViewState property provides the StateBag collection of state information.

Most Control methods are used transparently by the ASP.NET framework, such as Render( ), which generates the HTML output of a control, and LoadViewState( ) and SaveViewState( ), which manage view state automatically. One interesting method is DataBind( ), which binds controls to arrays or data tables. Third party controls can also extend these methods.

You can inherit from the Control class to create a simple ASP.NET control. Override the Render( ) method so that the control can generate its own output by using the supplied HtmlTextWriter. If you are creating a composite control, you must also override the CreateChildControls( ) method. Use this method to instantiate new server-based ASP.NET controls or LiteralControl objects and add them to the collection of child controls by using the Add( ) method. If you need to access child controls from another procedure, and you are not sure if they have been created yet, you can use the EnsureChildControls( ) method, which automatically calls CreateChildControls( ), if needed. You should also implement the INamingContainer interface to ensure that child controls are created in a distinct namespace.

Usually, it is easier to derive from System.Web.UI.WebControls.WebControl when creating a custom control, as this class provides basic style and color options and manages the state for these properties automatically. If your control does not provide user interface, you may want to derive from the more basic Control class.

public class Control : System.ComponentModel.IComponent, IDisposable, IParserAccessor, IDataBindingsAccessor {
// Public Constructors
   public Control( );
// Public Instance Properties
   public Control BindingContainer{get; }
   public virtual string ClientID{get; }
   public virtual ControlCollection Controls{get; }
   public virtual bool EnableViewState{set; get; }
   public virtual string ID{set; get; }
   public virtual Control NamingContainer{get; }
   public virtual Page Page{set; get; }
   public virtual Control Parent{get; }
   public ISite Site{set; get; }                    // implements System.ComponentModel.IComponent
   public virtual string TemplateSourceDirectory{get; }
   public virtual string UniqueID{get; }
   public virtual bool Visible{set; get; }
// Protected Instance Properties
   protected bool ChildControlsCreated{set; get; }
   protected virtual HttpContext Context{get; }
   protected EventHandlerList Events{get; }
   protected bool HasChildViewState{get; }
   protected bool IsTrackingViewState{get; }
   protected virtual StateBag ViewState{get; }
   protected virtual bool ViewStateIgnoresCase{get; }
// Public Instance Methods
   public virtual void DataBind( );
   public virtual void Dispose( );                   // implements IDisposable
   public virtual Control FindControl(string id);
   public virtual bool HasControls( );
   public void RenderControl(HtmlTextWriter writer);
   public string ResolveUrl(string relativeUrl);
   public void SetRenderMethodDelegate(RenderMethod renderMethod);
// Protected Instance Methods
   protected internal virtual void AddedControl(Control control, int index);
   protected virtual void AddParsedSubObject(object obj);       // implements IParserAccessor
   protected void BuildProfileTree(string parentId, bool calcViewState);
   protected void ClearChildViewState( );
   protected virtual void CreateChildControls( );
   protected virtual ControlCollection CreateControlCollection( );
   protected virtual void EnsureChildControls( );
   protected virtual Control FindControl(string id, int pathOffset);
   protected bool IsLiteralContent( );
   protected virtual void LoadViewState(object savedState);
   protected string MapPathSecure(string virtualPath);
   protected virtual bool OnBubbleEvent(object source, EventArgs args);
   protected virtual void OnDataBinding(EventArgs e);
   protected virtual void OnInit(EventArgs e);
   protected virtual void OnLoad(EventArgs e);
   protected virtual void OnPreRender(EventArgs e);
   protected virtual void OnUnload(EventArgs e);
   protected void RaiseBubbleEvent(object source, EventArgs args);
   protected internal virtual void RemovedControl(Control control);
   protected virtual void Render(HtmlTextWriter writer);
   protected virtual void RenderChildren(HtmlTextWriter writer);
   protected virtual object SaveViewState( );
   protected virtual void TrackViewState( );
// Events
   public event EventHandler DataBinding;
   public event EventHandler Disposed;              // implements System.ComponentModel.IComponent
   public event EventHandler Init;
   public event EventHandler Load;
   public event EventHandler PreRender;
   public event EventHandler Unload;


Multiple types

Returned By

BuildMethod.{EndInvoke( ), Invoke( )}, ControlCollection.{Owner, this}, System.Web.UI.Design.ControlParser.ParseControl( ), DesignTimeTemplateParser.ParseControl( ), System.Web.UI.MobileControls.Form.ControlToPaginate, PartialCachingControl.CachedControl, TemplateControl.{LoadControl( ), ParseControl( )}, System.Web.UI.WebControls.CheckBoxList.FindControl( )

Passed To

Multiple types

      Previous Section Next Section