vb.net barcode generator source code Practice: Updating Existing Code to Use Isolated Storage in VS .NET

Painting Denso QR Bar Code in VS .NET Practice: Updating Existing Code to Use Isolated Storage

Practice: Updating Existing Code to Use Isolated Storage
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Page 4-29
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Exercise
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1. How could you rewrite the following piece of code to store the information in isolated storage, isolated by user, domain, and assembly
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using System;
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using System.IO;
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StreamWriter sw = File.CreateText( mytemp.txt );
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sw.WriteLine( Hello, world! );
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sw.Close();
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Imports System.IO
Dim sw As StreamWriter = File.CreateText( mytemp.txt )
sw.WriteLine( Hello, world! )
sw.Close()
Questions and Answers
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There are several ways to write the code. However, the following code would work:
C# VB
using System;
using System.IO;
using System.IO.IsolatedStorage;
StreamWriter sw = new StreamWriter(new
IsolatedStorageFileStream( mytemp.txt", FileMode.CreateNew));
sw.WriteLine( Hello, world! );
sw.Close();
Imports System.IO
Imports System.IO.IsolatedStorage
Dim sw As StreamWriter = New StreamWriter(New
IsolatedStorageFileStream( mytemp.txt",FileMode.CreateNew))
sw.WriteLine( Hello, world! )
sw.Close()
Although the exact code you create might vary from this answer, the key difference between the original code and the code you create must be that the StreamWriter construction uses the overloaded method that accepts an IsolatedStorageFileStream object.
Lab: Taking Advantage of Platform Security
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Exercise
1. What approaches can you take to resolve the problem of writing to an inaccessible location in the registry Which approach would you recommend
There are several different approaches:
Modify the setup procedure to grant the Users group the right to update the
HKEY_LOCAL_MACHINE\Software\Fabrikam\ registry key. The setup procedure will need to be run by a member of the Administrators group.
Change the application to use the HKEY_CURRENT_USER\Software\Fabrikam key. Mem-
bers of the Users group can update this key by default.
Store information in a location other than the registry, such as the file system, or in the
database itself. In this case, the best solution is to store the information in the HKEY_CURRENT_USER\Software\Fabrikam key. This requires only a minimal change to the application. The most significant drawback to this approach is that the application must create the key for every user who logs on to the computer.
4-52
4
Taking Advantage of Platform Security
2. What approaches can you take to resolve the problem of writing to the inaccessible location on the file system Which approach would you recommend
There are three approaches:
Modify the setup procedure to grant the Users group the right to add and update new files
in the C:\Windows\ directory. The setup procedure will need to be run by a member of the Administrators group.
Change the application to use a directory that members of the Users group can add files
to, such as C:\Windows\Temp\.
Store files in the .NET Framework s isolated storage mechanism.
The first option is clearly wrong, because granting additional rights would reduce the security of the computer. The second option would work and be very easy to implement, because it would require only changing the path in the application. The third option would also work, and would provide additional security by isolating the data stored in the temporary files. However, the third option also would require additional programming to cause the application to use isolated storage rather than access the file system directly. Therefore either the second or third options are valid answers.
5 Implementing Role-Based Security
Why This Matters
Everyone is familiar with the concept of role-based security (or RBS, and also known as role access security), although you might not know the term. Rolebased security is the process of authenticating users and then authorizing them based on the permissions assigned to their user accounts and group memberships. In 4, Taking Advantage of Platform Security, you learned how to restrict access to files and folders based on a user s account and group memberships. This approach is perfect for systems administrators who are restricting access to data. However, developers need to be able to use RBS to restrict access to parts of an application. This chapter focuses on implementing RBS by using the .NET Framework. First, you explore how authentication and authorization are related. Next, you learn to examine a user s credentials to restrict access to parts of your application based on that user s group memberships. Then, you learn how to create custom authentication methods to allow you to authenticate users against a database or any other mechanism. Exam Objectives in this :
Write authorization code.
Programmatically control access to functionality and data by using user information such as user identity, group membership, and other custom user information.
Implement authentication.
Implement a custom authentication mechanism in a Microsoft Windows Forms application. Implement functionality by consuming authenticated user information such as the IPrincipal, Membership, and Identity components of the .NET base class library.
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