Visual Web Part && Visual Web Part User Control Life Cycle

Visual Web Part Life Cycle

I did create one visual web part with name “SimpleVisualWebPart”. It has the following code to display the sequence of life cycle events.

SimpleVisualWebPart.cs using System; using System.ComponentModel; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using Microsoft.SharePoint; using Microsoft.SharePoint.WebControls; using System.Diagnostics; namespace SPVisualWebParts.SimpleVisualWebPart {     [ToolboxItemAttribute(false)]     public class SimpleVisualWebPart : WebPart     {         // Visual Studio might automatically update this path when you change the Visual Web Part project item.         private const string _ascxPath = @"~/_CONTROLTEMPLATES/SPVisualWebParts/SimpleVisualWebPart/SimpleVisualWebPartUserControl.ascx";         private Label labelEvents = default(Label);         private SimpleVisualWebPartUserControl control;         string controlEvents;         protected override void CreateChildControls()         {             control = Page.LoadControl(_ascxPath) as SimpleVisualWebPartUserControl;             Debug.WriteLine("SimpleVisualWebPart - CreateChildControls");             Controls.Add(control);                   }         protected override void OnInit(EventArgs e)         {             base.OnInit(e);             Debug.WriteLine("SimpleVisualWebPart - OnInit");         }         protected override void OnLoad(EventArgs e)         {             base.OnLoad(e);             Debug.WriteLine("SimpleVisualWebPart - OnLoad");         }         protected override void LoadViewState(object savedState)         {             base.LoadViewState(savedState);             Debug.WriteLine("SimpleVisualWebPart - LoadViewState");         }         protected override void OnPreRender(EventArgs e)         {             base.OnPreRender(e);             Debug.WriteLine("SimpleVisualWebPart - OnPreRender");         }         protected override void RenderContents(HtmlTextWriter writer)         {             base.RenderContents(writer);             Debug.WriteLine("SimpleVisualWebPart - RenderContents");         }         protected override void OnUnload(EventArgs e)         {             base.OnUnload(e);             Debug.WriteLine("SimpleVisualWebPart - OnUnload");         }         protected override object SaveControlState()         {             Debug.WriteLine("SimpleVisualWebPart - SaveControlState");             return base.SaveControlState();         }         protected override object SaveViewState()         {             Debug.WriteLine("SimpleVisualWebPart - SaveViewState");             return base.SaveViewState();         }         protected override void Render(HtmlTextWriter writer)         {             Debug.WriteLine("SimpleVisualWebPart - Render");             base.Render(writer);         }         public override void Dispose()         {             Debug.WriteLine("SimpleVisualWebPart - Dispose");             base.Dispose();         }     } }

SimpleVisualWebPartUserControl.ascx.cs using System; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Diagnostics; namespace SPVisualWebParts.SimpleVisualWebPart {     public partial class SimpleVisualWebPartUserControl : UserControl     {         protected void Page_Load(object sender, EventArgs e)         {             Debug.WriteLine("SimpleVisualWebPartUserControl - Page_Load");         }               protected override void OnInit(EventArgs e)         {             Debug.WriteLine("SimpleVisualWebPartUserControl - OnInit");             base.OnInit(e);         }         protected override void LoadViewState(object savedState)         {             Debug.WriteLine("SimpleVisualWebPartUserControl - LoadViewState");             base.LoadViewState(savedState);         }         protected override void OnLoad(EventArgs e)         {             Debug.WriteLine("SimpleVisualWebPartUserControl - OnLoad");             base.OnLoad(e);         }         protected override void OnPreRender(EventArgs e)         {             Debug.WriteLine("SimpleVisualWebPartUserControl - OnPreRender");             base.OnPreRender(e);         }         protected override object SaveViewState()         {             Debug.WriteLine("SimpleVisualWebPartUserControl - SaveViewState");             return base.SaveViewState();         }         protected override void Render(HtmlTextWriter writer)         {             Debug.WriteLine("SimpleVisualWebPartUserControl - Render");             base.Render(writer);         }         public override void Dispose()         {             Debug.WriteLine("SimpleVisualWebPartUserControl - Dispose");             base.Dispose();         }         protected override void OnUnload(EventArgs e)         {             Debug.WriteLine("SimpleVisualWebPartUserControl - OnUnload");             base.OnUnload(e);         }     } }

I have captured entire life cycle events in the output window. Here is the output of sequence of life cycle events for the visual web part.

Output: SimpleVisualWebPart                                    - OnInit SimpleVisualWebPart                                    - OnLoad SimpleVisualWebPart                                    - CreateChildControls SimpleVisualWebPartUserControl                            - OnInit SimpleVisualWebPartUserControl                            - OnLoad SimpleVisualWebPartUserControl                            - Page_Load SimpleVisualWebPart                                    - OnPreRender SimpleVisualWebPartUserControl                            - OnPreRender SimpleVisualWebPart                                    - SaveViewState SimpleVisualWebPartUserControl                            - SaveViewState SimpleVisualWebPart                                    - Render SimpleVisualWebPartUserControl                            - Render SimpleVisualWebPart                                    - RenderContents SimpleVisualWebPartUserControl                            - OnUnload SimpleVisualWebPartUserControl                            - Dispose SimpleVisualWebPart                                    - OnUnload SimpleVisualWebPart                                    - Dispose

Web Part Life cycle

Event Phase	Description	Method or event to override
OnInit	Configuration values set using WebBrowsable properties and those in web part task	Init event (OnInit method)
LoadViewState	The view state of the web part is populated over here.	LoadViewState method
CreateChildControls OnLoad	All the specified controls are created and added to the controls collection. When the page is being rendered for the first time CreateChildControls occurs after the OnLoad event.  In case of postback it is called before the OnLoad() event.  We can make use of EnsureChildControls() – It checks to see if the CreateChildControls() has yet been called, and if it has not, calls it.	Load event (OnLoad method)
User generated event	Fires for events like button click	RaisePostBackEvent method
On PreRender	We can change any web part properties before the control output is drawn.	PreRender event (OnPreRender method)
RenderContents	HTML output is generated to render the output.	SaveViewState method
SaveViewState	ViewState of the web part is serialized and saved.	Render method
Dispose	Perform any final cleanup before the control is torn down. References to expensive resources such as database connections must be released in this phase.	Dispose method
Unload	Perform any final cleanup before the control is torn down. Control authors generally perform cleanup in Dispose and do not handle this event.	UnLoad event (On UnLoad

Web User Control Life cycle

Event Phase	Description	Method or event to override
Initialize	Initialize settings needed during the lifetime of the incoming Web request.	Init event (OnInit method)
Load view state	At the end of this phase, the ViewStateproperty of a control is automatically populated. A control can override the default implementation of theLoadViewState method to customize state restoration.	LoadViewState method
Load	Perform actions common to all requests, such as setting up a database query. At this point, server controls in the tree are created and initialized, the state is restored, and form controls reflect client-side data.	Load event (OnLoad method)
Handle postback events	Handle the client-side event that caused the postback and raise appropriate events on the server. Note   Only controls that process postback events participate in this phase.	RaisePostBackEvent method
Prerender	Perform any updates before the output is rendered. Any changes made to the state of the control in the prerender phase can be saved, while changes made in the rendering phase are lost.	PreRender event (OnPreRender method)
SaveViewState	The ViewState property of a control is automatically persisted to a string object after this stage. This string object is sent to the client and back as a hidden variable. For improving efficiency, a control can override the SaveViewState method to modify the ViewState property.	SaveViewState method
Render	Generate output to be rendered to the client.	Render method
Dispose	Perform any final cleanup before the control is torn down. References to expensive resources such as database connections must be released in this phase.	Dispose method
Unload	Perform any final cleanup before the control is torn down. Control authors generally perform cleanup in Dispose and do not handle this event.	UnLoad event (On UnLoad