Tutorial asp.net

Tutorial: ASP.Net for Master of Computer
Application Students
Prepared by Vivek Kumar Singh

Exercise 1: Create PublicPage.aspx
Use Notepad or the text editor of your choice to create a text file named PublicPage.aspx in
your PC’s Inetpubwwwroot directory. Then add the following text to create a simple Web
form:

<html>
<body>
<h1>Public Page</h1>
<hr>
<form runat="server">
<asp:Button Text="View Secret Message"
OnClick="OnViewSecret" RunAt="server" />
</form>
</body>
</html>

<script language="C#" runat="server">
void OnViewSecret (Object sender, EventArgs e)
{
Response.Redirect ("Secret/ProtectedPage.aspx");
}
</script>

Exercise 2: Create ProtectedPage.aspx
Create a new directory named Secret in Inetpubwwwroot. In it, create a text file named
ProtectedPage.aspx and enter the following code:

<html>
<body>
<h1>Protected Page</h1>
<hr>
<br>
Be careful investing your money in dot-coms.
</body>
</html>

Exercise 3: Test
Test what you’ve done so far by opening PublicPage.aspx in your browser and clicking the
“View Secret Message” button. In response, ProtectedPage.aspx should be loaded and should
display a secret message for you.

Exercise 4: Create Web.config
Create a text file named Web.config in Inetpubwwwroot and enter the following statements:

<configuration>
<system.web>
<authentication mode="Forms">

<forms loginUrl="LoginPage.aspx">
<credentials passwordFormat="Clear">
<user name="Jeff" password="hawkeye" />
<user name="John" password="redrover" />
</credentials>
</forms>
</authentication>
<authorization>
<allow users="?" />
</authorization>
</system.web>
</configuration>

The <authentication> section of this configuration file enables forms authentication,
designates LoginPage.aspx as the page that users must go through to get to protected
resources, and defines two sets of login credentials. The <authorization> section grants
anonymous users access to all parts of this site that don’t specify otherwise.

Exercise 5: Create LoginPage.aspx
Create a text file named LoginPage.aspx in Inetpubwwwroot and enter the following
statements:

<html>
<body>
<h1>Please Log In</h1>
<hr>
<table cellpadding="8">
<tr>
<td>
User Name:
</td>
<td>
<asp:TextBox ID="UserName" RunAt="server" />
</td>
</tr>
<tr>
<td>
Password:
</td>
<td>
<asp:TextBox ID="Password" RunAt="server" />
</td>
</tr>
<tr>
<td>
<asp:Button Text="Submit" OnClick="OnSubmit" RunAt="server" />
</td>
<td>
</td>
</tr>
</table>
</form>
<hr>
<h3><asp:Label ID="Output" RunAt="server" /></h3>
</body>
</html>

<script language="C#" runat="server">
void OnSubmit (Object sender, EventArgs e)

{
if (FormsAuthentication.Authenticate (UserName.Text, Password.Text))
FormsAuthentication.RedirectFromLoginPage (UserName.Text, false);
else
Output.Text = "Invalid login";
}
</script>

This page displays a simple login form that accepts a user name and password. Clicking the
Submit button activates OnSubmit, which uses the Authenticate method of the
FormsAuthentication class (a member of the .NET Framework Class Library’s
System.Web.Security namespace) to authenticate the supplied user name and password
against the credentials defined in the <credentials> section of Web.config. If the login is
approved, FormsAuthentication.RedirectFromLoginPage is called to send the user to the page
protected by the login page.

Exercise 6: Test
Verify that the application still works as it did before by opening PublicPage.aspx again and
clicking the “View Secret Message” button. Because you’ve yet to restrict access to
ProtectedPage.aspx, the secret message should appear in the browser window.

Exercise 7: Create another Web.config file
Create another text file named Web.config, this time in the Secret directory
(Inetpubwwwrootsecret). Add the following statements to deny anonymous users access to
files in this directory:

<configuration>
<system.web>
<authorization>
<deny users="?" />
</authorization>
</system.web>
</configuration>

Exercise 8: Test
Repeat the test you performed in Exercise 6 and verify that clicking the “View Secret Message”
button causes your login page to appear (see below). Type “Jeff” into the User Name box and
“imbatman” into the Password box. Then click Submit. Does the secret message appear? Why
or why not? Finish up by entering the user name “Jeff” and the password “hawkeye.” Do you
see ProtectedPage.aspx this time?

Exercise 9: Modify the top-level Web.config file
Close Internet Explorer and reopen it (important!). Then delete the <credentials> section from
the top-level Web.config file—the one in Inetpubwwwroot. Test the application again by
clicking the “View Secret Message” button. Can you get past the login page?

Exercise 10: Create an authentication database
While it’s perfectly possible to secure ASP.NET applications using credentials stored in
Web.config, doing so isn’t very realistic unless you plan to authorize access to only a small
number of users. In the real world, it makes sense to store authentication data in a database,
and to write the login page so that it authenticates against the database rather than against
Web.config.

To that end, open a command prompt window, go to the folder where Weblogin.sql is stored,
and type

osql –U sa –P –i weblogin.sql

This command executes the script found in Weblogin.sql, which creates a new SQL Server
database named WebLogin. Inside the database is a table named Credentials that contains the
following records:

UserName Password

Jeff hawkeye

John redrover

Before proceeding, use the SQL Server Query Analyzer (or the tool of your choice) to verify
that the database was properly created and initialized.

Note: Weblogin.sql assumes that SQL Server is installed on drive C: on your PC. If you
installed SQL Server on a different drive, open Weblogin.sql and edit the statement

FILENAME = 'C:program files...weblogin.mdf'

to include the correct drive letter.

Exercise 11: Add a CustomAuthenticate method and modify OnSubmit
Add the following statements to the top of LoginPage.aspx:

<%@ Import NameSpace="System.Data" %>
<%@ Import NameSpace="System.Data.SqlClient" %>

Then add the following method to the <script> block:

bool CustomAuthenticate (string username, string password)
{
SqlDataAdapter adapter =
new SqlDataAdapter ("select password from credentials " +
"where username = '" + username + "'",
"server=localhost;uid=sa;pwd=;database=weblogin");
DataSet ds = new DataSet ();
adapter.Fill (ds);

DataTable table = ds.Tables[0];

foreach (DataRow row in table.Rows) {
string pw = row[0].ToString ().TrimEnd (new char[] { ' ' });
if (String.Compare (password, pw, false) == 0)
return true;
}
return false;
}

Finally, modify the OnSubmit method so that it calls CustomAuthenticate instead of
FormsAuthentication.Authenticate:

void OnSubmit (Object sender, EventArgs e)
{
if (CustomAuthenticate (UserName.Text, Password.Text))
else
Output.Text = "Invalid login";
}

CustomAuthenticate uses ADO.NET to perform a database query and validate the user name
and password provided to it.

Exercise 12: Test
Restart your browser again. Then test the application again by clicking the “View Secret

Message” button and entering one of the sets of credentials included in the WebLogin
database. Verify that you can once more get to ProtectedPage.aspx.

Exercise 13: Try This
Go back to PublicPage.aspx in your browser and click “View Secret Message” again. Verify that
you go straight to ProtectedPage.aspx without having to enter a user name and password
again.

Now close your browser and restart it. Open PublicPage.aspx and click the “View Secret
Message” button. Because the authentication cookie issued to you when you logged in was a
temporary one, you’ll have to log in again to get to the protected page.

Exercise 14: Make the authentication cookie persistent
When you pass FormsAuthentication.RedirectFromLoginPage a second parameter that equals
false, like this:


RedirectFromLoginPage issues a temporary cookie, or session cookie, that expires when the
browser is closed. If you pass true instead, RedirectFromLoginPage issues a persistent cookie
that’s good for 50 years. Demonstrate by doing the following:

1. Change RedirectFromLoginPage’s second parameter to true.
2. Restart your browser and open PublicPage.aspx.
3. Click the “View Secret Message” button and log in.
4. Verify that the secret message is displayed.
5. Close your browser.
6. Restart the browser, open PublicPage.aspx, and click “View Secret Message.”

Because the cookie is now being cached on your hard disk, you shouldn’t have to log in again
in step 6. Finish up by doing the following:

1. Use Internet Explorer’s Tools/Internet Options/General/Delete Cookies command to
delete all the cookies on your PC.
2. Open PublicPage.aspx and click “View Secret Message.”

This time, you will have to log in because when you deleted the cookies on your PC, you
deleted the authentication cookie, too.

Exercise 15: Let the user decide
Add a “Remember me” check box to LoginPage.aspx that lets the user decide whether to make
the authentication cookie persistent (if the box is checked) or temporary (if the box isn’t
checked), as shown below.

To add the check box, modify the form as follows:

<table cellpadding="8">
<tr>
<td>
User Name:
</td>
<td>
<asp:TextBox ID="UserName" RunAt="server" />
</td>
</tr>
<tr>
<td>
Password:
</td>
<td>
<asp:TextBox ID="Password" RunAt="server" />
</td>
</tr>
<tr>
<td>
<asp:Button Text="Submit" OnClick="OnSubmit"RunAt="server" />
</td>
<td>
<asp:CheckBox Text="Remember me" ID="RememberMe" RunAt="server" />
</td>
</tr>
</table>
</form>

And, so that the check box will be honored, change the second parameter passed to
RedirectFromLoginPage to RememberMe.Checked:

FormsAuthentication.RedirectFromLoginPage (UserName.Text,
RememberMe.Checked);

Checked is a CheckBox property that indicates whether the box is checked (true) or unchecked
(false).

Exercise 16: Test
Test the changes you made in Exercise 15 by verifying that:

1. If the “Remember me” button isn’t checked and you restart your browser, you have to
log in again to view ProtectedPage.aspx.
2. If the “Remember me” button is checked and you restart your browser, you don’t have
to log in again to view ProtectedPage.aspx.

Exercise 17: Personalize the secret message
Modify ProtectedPage.aspx so that it prefaces the secret message with the user’s login name.
Here’s the modified file, with changes highlighted in bold:

<%@ Page Language="C#" %>

<html>
<body>
<h1>Protected Page</h1>
<hr><br>
<% Response.Write (Context.User.Identity.Name + ": "); %>
Be careful investing your money in dot-coms.
</body>
</html>

Exercise 18: Change the cookie’s expiration date
Modify OnSubmit so that if “Remember me” is checked, the authentication cookie that’s issued
has a lifetime of 7 days instead of 50 years. The key is to replace the call to
RedirectFromLoginPage with the following statements:

HttpCookie cookie = FormsAuthentication.GetAuthCookie (UserName.Text,
RememberMe.Checked);
cookie.Expires = DateTime.Now + new TimeSpan (7, 0, 0, 0);
Response.Cookies.Add (cookie);
Response.Redirect (FormsAuthentication.GetRedirectUrl (UserName.Text,
RememberMe.Checked));

The first statement creates an authentication cookie; the second sets the cookie’s expiration
date to one week from the current date; the third adds the cookie to the Response object’s
Cookies collection, ensuring that the authentication cookie will be returned in the response;
and the fourth and final statement redirects to the page that the user requested before the
login form popped up.

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