New ASP.NET Web Application: has a Login button that does something - but, where does the magic happen?

Question

Forgive my somewhat-lacking ASP.NET knowledge for this question :)

Here's the scenario: I'm playing around in VS2010, I've created a new ASP.NET Web Application (under Visual C#, Web templates). Nothing special, just a basic web application. No fancy MVC stuff.

Included in the template-generated solution is a Login page; Account/Login.aspx. On that page, is a Login button; the HTML looks like this:

<p class="submitButton">
    <asp:Button ID="LoginButton"
                runat="server"
                CommandName="Login"
                Text="Log In"
                ValidationGroup="LoginUserValidationGroup"/>
</p>

Again, nothing fancy. Now, the code behind:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Account_Login : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        RegisterHyperLink.NavigateUrl = "Register.aspx?ReturnUrl=" + HttpUtility.UrlEncode(Request.QueryString["ReturnUrl"]);
    }
}

Even less fancy. And finally, from web.config:

    <authentication mode="Forms">
        <forms loginUrl="~/Account/Login.aspx" timeout="2880"/>
    </authentication>

So, here is what I can't quite figure out: when I run the app, I can click the Login button, and the app does something - but where is the code for that something?

Coming from the WPF world (with some background in ASP.NET), my first instinct is to zero-in on CommandName - but a search for anything relating to "Login" turns up dry. My second instinct is to look at the code-behind, but again, it's pretty sparse and I don't see anything that looks like it has anything to do with a Login button being clicked.

So where does the "magic" behind this button happen? There has to be something; I feel like I've overlooked something that is sitting right in front of my eyes.

Answer 1

If you're referring to the Default Web Application (not the empty) that comes out of the box with Visual Studio, you'll notice that login button is inside an <asp:Login> server control. That's where the magic is happening. It interfaces with the ASP.NET Membership provider if you look in the web.config, you'll see references to that.

Answer 2

The page is posting back. but there is no event handler wired up so it doesn't do anything. I knows how to do this by the code that gets generated when the button is added. The button is generating some JavaScript code that calls a function to post-back the page.

You'll need to add an event handler. The easiest way is just to double-click the button on the form designer and it will generate the code for you.

Answer 3

The Button is a server side control - this causes it to post back when clicked.

If you look at the source of the page, you will see a call to __dopostback, a javascript function that posts the page back to itself.

At this point, the page reloads, which is probably what you are seeing.