C# 4 and .NET 4

552 ❘ ChaPTer 21 security
The Windows application just uses Label, TextBox, PasswordBox,
and Button controls, as shown in Figure 21-1. The Label with
the content User Validated shows up only when the logon is
successful.
The handler of the Button.Click event invokes the ValidateUser()
method of the Membership class. Because of the configured provider
ClientAuthenticationMembershipProvider, the provider in turn
invokes the Web service and calls the method ValidateUser() of the
SampleMembershipProvider class to verify a successful logon. With
success, the Label labelValidatedInfo is made visible; otherwise, a
message box pops up:
private void OnLogin(object sender, RoutedEventArgs e)
{
try
figure 21-1
{
if (Membership.ValidateUser(textUsername.Text,
textPassword.Password))
{
// user validated!
labelValidatedInfo.Visibility = Visibility.Visible;
}
else
{
MessageBox.Show("Username or password not valid",
"Client Authentication Services", MessageBoxButton.OK,
MessageBoxImage.Warning);
}
}
catch (WebException ex)
{
MessageBox.Show(ex.Message, "Client Application Services",
MessageBoxButton.OK, MessageBoxImage.Error);
}
}
code snippet AuthenticationServices/app.config
code snippet AuthenticationServices/MainWindow.xaml.cs
enCryPTion
Confidential data should be secured so that it cannot be read by unprivileged users. This is valid both
for data that is sent across the network, or stored data. You can encrypt such data with symmetric or
asymmetric encryption keys.
With a symmetric key, the same key can be used for encryption and decryption. With asymmetric
encryption, different keys are used for encryption and decryption: a public and a private key. Something
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