ASP.NET Tutorial/Page Lifecycle/Page Events

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Error event example

<%@ Page Language="vb" %>
<html>
   <head>
      <title>Error event example</title>
      <script runat="server">
         Sub Page_Load()
            Dim x, y, overflow As Integer
            x = 1
            y = 0
            overflow = x / y
         End Sub
         Sub Page_Error()
            Response.Write(Server.GetLastError.ToString())
            Server.ClearError
         End Sub
      </script>
   </head>
<body>
   <asp:label id="Message" runat="server"/>
</body>
</html>


Here is the sequence of events that are raised whenever you request a page:

1. PreInit
   2. Init
   3. InitComplete
   4. PreLoad
   5. Load
   6. LoadComplete
   7. PreRender
   8. PreRenderComplete
   9. SaveStateComplete
  10. Unload

<%@ 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 Page_Load(object sender, EventArgs e)
    {
        Label1.Text = "Page Load";
    }
    void Button1_Click(object sender, EventArgs e)
    {
        Label1.Text += "<br />Button Click";
    }
    void Page_PreRender()
    {
        Label1.Text += "<br />Page PreRender";
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Page Events</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:Button
        id="Button1"
        Text="Click Here"
        OnClick="Button1_Click"
        Runat="server" />
    <br /><br />
    <asp:Label
        id="Label1"
        Runat="server" />
    </div>
    </form>
</body>
</html>


Page events firing sequence (VB.net)

<%@ 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 Page_Load()
        Label1.Text = "Page Load"
    End Sub
    Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
        Label1.Text &= "<br />Button Click"
    End Sub
    Sub Page_PreRender()
        Label1.Text &= "<br />Page PreRender"
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Page Events</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    
    <asp:Button
        id="Button1"
        Text="Click Here"
        OnClick="Button1_Click"
        Runat="server" />
    
    <br /><br />
    
    <asp:Label
        id="Label1"
        Runat="server" />
    
    </div>
    </form>
</body>
</html>


Page flow tracing

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="PageFlowTracing" Trace="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>Page Flow</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:Label id="lblInfo" 
               runat="server" EnableViewState="False"/>
    <asp:Button id="Button1" 
                runat="server"
                Text="Button" OnClick="Button1_Click"/>
    </div>
    </form>
</body>
</html>
File: Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class PageFlowTracing : System.Web.UI.Page
{
  private void Page_Load(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.Load event handled.<br/>";
    if (Page.IsPostBack)
    {
      lblInfo.Text += "<b>This is the second time you"ve seen this page.</b><br/>";
    }
  }
  private void Page_Init(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.Init event handled.<br/>";
  }
  protected void Button1_Click(object sender, System.EventArgs e)
  {
    Trace.Write("Button1_Click", "About to update the label.");
    lblInfo.Text += "Button1.Click event handled.";
    Trace.Write("Button1_Click", "Label updated.");
  }
  private void Page_PreRender(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.PreRender event handled.<br/>";
  }
  private void Page_Unload(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.Unload event handled.<br/>";
  }
}


Page life cycle events

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="PageFlow" %>
<!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>Page Flow</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Label id="lblInfo" runat="server" EnableViewState="False">
         </asp:Label>
            <asp:Button id="Button1" runat="server"
              Text="Button" OnClick="Button1_Click"></asp:Button>
    </div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class PageFlow : System.Web.UI.Page
{
  private void Page_Load(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.Load event handled.<br/>";
    if (Page.IsPostBack)
    {
      lblInfo.Text += "<b>second time</b><br/>";
    }
  }
  private void Page_Init(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.Init event handled.<br/>";
  }
  protected void Button1_Click(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Button1.Click event handled.<br/>";
  }
  private void Page_PreRender(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.PreRender event handled.<br/>";
  }
  private void Page_Unload(object sender, System.EventArgs e)
  {
    lblInfo.Text += "Page.Unload event handled.<br/>";
  }
}


Unload event example

<%@ Page Language="vb" %>
<html>
   <head>
      <title>Unload event example</title>
      <script runat="server">
         Dim TheFile As System.IO.StreamReader
         Sub Page_Load()
            TheFile = System.IO.File.OpenText(MapPath("Init.aspx"))
            Message.Text = "<pre>" & Server.HtmlEncode(TheFile.ReadToEnd()) & "</pre>"
         End Sub
         Sub Page_Unload()
            TheFile.Close()
         End Sub
      </script>
   </head>
<body>
   <asp:label id="Message" runat="server"/>
</body>
</html>
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/Page_Lifecycle/Page_Events&oldid=3199»