create qr barcode c# Objective 1.1 in .net C#

Produce QR in .net C# Objective 1.1

14-12

The following questions are intended to reinforce key information presented in this lesson. If you are unable to answer a question, review the lesson materials and try the question again. You can find answers to the questions in the Questions and Answers section at the end of this chapter. 1. List the caching options that are available when you make a shared folder available offline on the computer sharing the file.

Secondary indexing is simply the task of determining other indexes to add to a database to make queries more efficient. It is called secondary indexing because when you defined the identifiers earlier in this chapter, every table in your schema got a primary key index to make searching by primary key very efficient. There is a cost for indexing in that as new values are added to your tables, the indexes must be updated with any new values that must be indexed. With this in mind, you will want to create as few indexes per table as possible but add indexes judiciously where necessary. You are probably responsible for making sure that indexing is efficient when you recommend a data schema. That doesn t mean that you can t elicit advice. If your company employs database administrators, you should use them to help you make smart indexing decisions. When you want to determine what secondary indexes you need, you will want to look at what types of data in the schema are likely to cause searches that do not use the primary key. For example, you might choose to add an index on the Order table s OrderNumber field so that searching for an order by its order number is a fast search. Adding secondary indexes during the design mode can only get you so far. Typically, indexes will need to be tweaked once a project is delivered to help make real-world searches perform better. Using tools like SQL Server Profiler and SQL Server Database Tuning Wizard will help improve the performance of a running database.

For details about all the practice test options available, see the How to Use the Practice Tests section in this book s Introduction.

2

Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Defines an UPDATE or DELETE action on rows that exist in the target table but not in the source. Like the WHEN MATCHED clause, a MERGE statement can include up to two WHEN NOT MATCHED BY SOURCE clauses, and when two exist, one must be defined as an UPDATE and the other is defined as a DELETE. When no rows are returned by the source table, columns in the source table cannot be referenced in the <merge_matched> clause or an error 207 (invalid column name) is returned.

Because of the time that it takes for Microsoft to test device drivers before signing them, the most recent drivers available from a manufacturer are rarely signed. If you are managing a small number of computers, you are usually better off not worrying too much about driver signing and just using the most recent driver available from the manufacturer of a device because newer drivers are likely to have bug fixes and improvements that are worth having. Just make sure that you acquire the drivers directly from the vendor. If you are managing a large installation of computers, though, the small risk associated with using unsigned drivers becomes significant enough that it is probably better to wait for the signed drivers to come out.

What do you think of this book We want to hear from you!

CloseServiceHandle(hService); CloseServiceHandle(hSCManager);

15-6

You can use either Exchange Management Console or Exchange Management Shell to configure the properties of a distribution group. For example, you can configure message size restrictions for both universal and dynamic distribution groups, or you can remove a member from or add a member to a universal distribution group. Note that you cannot remove members from or add members to a dynamic distribution group because membership is not fixed and a list of members is created whenever an e-mail message is sent to the group.

Even with the wide variety (okay, five) of system sounds that can be played, sometimes additional sounds might be required. For these times, the SoundPlayer class (also part of the System.Media namespace) can be used. First of all, the SoundPlayer class is limited in that only WAV files can be played. But within that limitation, the SoundPlayer class exposes a number of useful features. In terms of specifying the location of the WAV file, the SoundLocation property is used. This property can be assigned a file path, a Universal Naming Convention (UNC) path, or even a Uniform Resource Locator (URL). Given the fact that the sound could be located on a URL (that is, on a remote Web site), the speed at which the file is available might have an impact on how the sound is delivered. To accommodate this, sound can be played in a number of ways. If the location of the sound is close to the application playing the sound, then the Play method on the SoundPlayer class can be used. This simply loads the WAV file and plays it. One of the convenient (and unexpected) features of the Play method is that although it is synchronous, it does not block the current thread. Instead, a separate thread is created and the file is loaded and played on that thread. This keeps a large or slowly loading WAV file from blocking the application, which is an important consideration if the SoundPlayer were to be invoked from within a Windows Forms application because in that case blocking the main thread would result in the application appearing to hang.

1-18