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Visual Web Part Life Cycle

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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 ViewState property of a control is automatically populated. A control can override the default implementation of the LoadViewState 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

Comments

  • Anonymous
    October 14, 2012
    Thanks..it's very helpful

  • Anonymous
    December 13, 2012
    Thanks you for Share,  it's good article

  • Anonymous
    December 23, 2012
    good article

  • Anonymous
    July 08, 2014
    Nice Explanation