asp.net qr code reader

asp.net qr code reader

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By creating your own authentication class, you can perform authentication against any data source, including an XML file or a database. To create your own authenticator, you simply need to create a class that derives from UsernameTokenManager and overrides the AuthenticateToken() method. In this method, your code needs to look up the user who is trying to become authenticated and return the password for that user. ASP.NET will then compare this password against the user credentials and decide whether authentication fails or succeeds. Creating this class is quite straightforward. Here s an example that simply returns hard-coded passwords for two users. This provides a quick-and-easy test, although a real-world example would probably use ADO.NET code to get the same information. public class CustomAuthenticator : UsernameTokenManager { protected override string AuthenticateToken(UsernameToken token) { string username = token.Username; if (username == "dan") return "secret"; else if (username == "jenny") return "opensesame"; else return ""; } }

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In all these examples, the bound values are updated as soon as you tab out of the text box after modifying its text (in other words, when the JavaScript onchange event occurs). Finally, Atlas also introduces the concept of transformers, which extend data binding. Essentially, a transformer takes the data you re binding and reformats it. For example, you can use a transformer to add or multiply numbers, to invert a Boolean value, or to add text. More usefully, you can create custom transformers using JavaScript code. The following example uses the ToString transformer to place the text values into a full sentence: <label id="spanFirst"> <bindings> <binding dataContext="txtFirst" dataPath="text" property="text" transform="ToString" transformerArgument="Your full name is {0}" /> </bindings> </label> <label id="spanLast"> <bindings> <binding dataContext="txtLast" dataPath="text" property="text" transform="ToString" transformerArgument="{0}." /> </bindings> </label> Figure 35-11 shows the result.

The reason you don t perform the password test on your own is because the type of comparison depends on how the credentials are encoded. For example, if they are passed in clear text, you need to perform a simple string comparison. If they are hashed, you need to create a new password hash using the same standardized algorithm, which must take the same data into account (including the random nonce from the client message). However, the WSE can perform this comparison task for you automatically, which dramatically simplifies your logic. The only potential problem is that you need to have the user s password stored in a retrievable form on the web server. If you re storing only password hashes in a back-end database, you won t be able to pass the original password to ASP.NET, and it won t be able to re-create the credential hash it needs to authenticate the user. Once you ve created your authentication class, you still need to tell the WSE to use it for authenticating user tokens by registering your class in the web.config file. To accomplish this, right-click the project name in the Solution Explorer, and select WSE Settings. Next, select the Security tab (shown in Figure 34-11).

To test this page, request it in the browser, select some items in the list box, type some characters in the text box, select the check box, and click the submit button to generate a postback. You should end up with something similar to what s shown in Figure 4-5.

In this example, it s hard to see the benefit of Atlas script. It hardly seems worthwhile to write a whole chunk of tags to deal with updating an ordinary label, especially when the alternative is to use a few concise lines of JavaScript. However, you ll see the real advantage of Atlas script when you begin considering features that would be more difficult to implement in JavaScript. One example is data binding. Using Atlas script, you can quickly define a data binding relationship that tells Atlas how to fill a grid and handle operations such as record deletions, inserts, and updates. Once you define this relationship, Atlas will call the required server code automatically. Trying to design the same solution with pure JavaScript would take much more work.

To complete this example, create a simple text page, and add a DynamicPanel and a DynamicPanelRefreshLink underneath it. Set the DynamicPanelRefreshLink.PanelID property to create the link. Next, place some content and controls in the panel. Finally, add an event handler for the DynamicPanel.Refresh event and use it to change the content or formatting of the controls in the panel. protected void Panel1_Refres(object sender, EventArgs e) { Label1.Text = "This was refreshed without a postback at " + DateTime.Now.ToString(); } Now when you run the page, you ll see that you can click the DynamicPanelRefreshLink to refresh the panel without posting back the page (see Figure 34-19).