Wrapping exceptions with InnerException, Kyiv 2010

1_hiding_exception.cs

public class UserManager {
  public void Authenticate(string userName, string password) {
    try {
      _userDatabase.Authenticate(userName, password);
    } catch (Exception e) {
      // Now if authentication fails, when you catch AuthenticationFailedException
      // you have no idea what actually caused the authentication to fail.
      // That will make debugging, especially in the field, very hard
      throw new AuthenticationFailedException();
    }
  }
}

2_wrapping_exception.cs

public class UserManager {
  public void Authenticate(string userName, string password) {
    try {
      _userDatabase.Authenticate(userName, password);
    } catch (Exception e) {
      // This way, if you log the thrown exception, or look at it in the debugger, you will also see the inner exception
      // and its call stack, which will be much more helpful.
      throw new AuthenticationFailedException(e);
    }
  }
}

AuthenticationFailedException.cs

public class AuthenticationFailedException : ApplicationException {
  public AuthenticationFailedException() : base ("Authentication failed") {}

  public AuthenticationFailedException(Exception innerException) : base("Authentication failed", innerException) {}
}