Skip to main content

What is AutoEventWireup?


The ASP.NET page framework also supports an automatic way to associate page events and methods. If the AutoEventWireup attribute of the Page directive is set to true (or if it is missing, since by default it is true), 

  • AutoEventWireup is an attribute in Page directive.  
  • AutoEventWireup is a Boolean attribute that indicates whether the ASP.NET pages events are auto-wired. 
  • AutoEventWireup will have a value true or false. By default it is true.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication2._Default" %>


the page framework calls page events automatically, specifically the Page_Init and Page_Load methods. In that case, no explicit Handles clause or delegate is needed.

Example 1

With AutoEventWireup="true"

HTML Code

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication2._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
   
        <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
   
    </div>
    </form>
</body>
</html>

Code

protected void Page_Load(object sender, EventArgs e)
{
    Response.Write("IN");
}

protected void Button1_Click(object sender, EventArgs e)
{
    Response.Write("<br>Button Click");
}

When we click Button then both page load and button click event get fired.

OUTPUT

IN
Button Click





Example 2

With  AutoEventWireup="false"

Now set the AutoEventWireup propoerty false

<%@ Page Language="C#" AutoEventWireup="false" CodeBehind="Default.aspx.cs" Inherits="WebApplication2._Default" %>

Again click the Button Event this time only click event get fired.

OUTPUT

Button Click


Why my ASP.NET events fire twice?

A very common question asked. The simple answer to this question is:

If you have AutoEventWireup="true" as well as you also have defined delegates for the event handling in your code, .NET Framework will automatically call methods based on their names and also the methods you defined explicitly.


Disadvantages of AutoEventWireup attribute
  1. AutoEventWireup uses fixed naming convention for the events. Page events handlers have specific predictable names. This limits your flexibility in how you name event handlers.
  2. If you do set AutoEventWireup to true, Visual Studio will generate code to bind the events and the page framework will automatically call events based on their names. This can result in the same event code being called twice when the page runs. As a consequence, you should always leave AutoEventWireup set to false when working in Visual Studio.
  3. Another disadvantage is that performance is adversely affected, because ASP.NET searches for methods at run-time. For a Web site with high traffic volumes, the impact on performance could be significant.

Labels:

Comments

  1. lingmaakiMarch 20, 2019 at 10:21 PM

    The disadvantage of the AutoEventWireup attribute is that it requires that the page event handlers have specific, predictable names. This limits your flexibility in how you name your event handlers. Therefore, in Visual Studio, the AutoEventWireup attribute is set to false by default and the designer generates explicit code to bind page events to methods.

    More...Asp.Net Interview Questions

    ReplyDelete

Post a Comment

Popular posts from this blog

Connected and disconnected architecture in ADO.Net with Example

Connected Architecture of ADO.NET The architecture of ADO.net, in which connection must be opened to access the data retrieved from database is called as connected architecture. Connected architecture was built on the classes connection, command, datareader and transaction.  Connected architecture is when you constantly make trips to the database for any CRUD (Create, Read, Update and Delete) operation you wish to do. This creates more traffic to the database but is normally much faster as you should be doing smaller transactions. Disconnected Architecture in ADO.NET The architecture of ADO.net in which data retrieved from database can be accessed even when connection to database was closed is called as disconnected architecture. Disconnected architecture of ADO.net was built on classes connection, dataadapter, commandbuilder and dataset and dataview. Disconnected architecture is a method of retrieving a recor
35 comments
Read more

HTTPHandler and HTTPModule in ASP.NET

If you want to implement pre-processing logic before a request hits the IIS resources. For instance you would like to apply security mechanism, URL rewriting, filter something in the request, etc. ASP.NET has provided two types of interception HttpModule and HttpHandler .   The web server examines the file name extension of the requested file, and determines which ISAPI extension should handle the request. Then the request is passed to the appropriate ISAPI extension.  For Example When an .aspx page is requested it is passed to ASP.Net page handler. Then Application domain is created and after that different ASP.Net objects like Httpcontext, HttpRequest, HttpResponse. HTTPModule: -    It's just like a filter. The Modules are called before and after the handler executes . -    HTTP Modules are objects which also participate the pipeline but they work before and after the HTTP Handler does its job, and produce additional services within the pipeline -  
125 comments
Read more

ASP.NET Page Life Cycle with example

In this article, we are going to discuss the different methods and order they are executed during the load of an .aspx web page. Methods Description Page_PreInit Before page Initialization Page_Init Page Initialization LoadViewState View State Loading LoadPostData Postback Data Processing Page_Load Page Loading RaisePostDataChangedEvent PostBack Change Notification RaisePostBackEvent PostBack Event Handling Page_PreRender Page Pre Rendering Phase SaveViewState View State Saving Page_Render Page Rendering Page_Unload Page Unloading PreInit : The entry point of the page life cycle is the pre-initialization phase called “PreInit”. You can dynamically set the values of master pages and themes in this event. You can also dynamically create controls in this event.  Init : This event fires after each control h
5 comments
Read more