code 39 barcode font for crystal reports download

code 39 barcode font for crystal reports download

how to use code 39 barcode font in crystal reports

As you learned earlier in this chapter, you can bind to a DataReader or a DataView So, it s worth asking, which approach does the SqlDataSource control use It s actually in your control, based on whether you set the DataSourceMode to SqlDataSourceModeDataSet (the default) or to SqlDataSourceModeDataReader The DataSet mode is almost always better, because it supports advanced sorting, filtering, and caching settings that depend on the DataSet All these features are disabled in the DataReader mode However, you can use the DataReader mode with extremely large grids, as it s more memory-efficient That s because the DataReader holds only one record in memory at a time just long enough to copy the record s information to the linked control Both modes support binding to multiple controls To understand why this is possible, you need to take a closer look at how the selection is performed.

ASP .NET never serves requests for configuration files, because they often contain sensitive information. However, even with this basic restriction in place, you may want to increase security by encrypting sections of a configuration file. This is a recommended practice for data such as connections and user-specific details. (Of course, any passwords should also be encrypted, although ideally they won t be placed in a configuration file at all.) ASP.NET supports two encryption options: RSA: The RSA provider allows you to create a key pair that is then used to encrypt the configuration data. The advantage is that you can copy this key between computers (for example, if you want to use the same configuration file with all the servers in a web farm). The RSA provider is used by default. DPAPI: The DPAPI (data protection API) provider uses a protection mechanism that s built into Windows. Configuration files are encrypted using a machine-specific key. The advantage is that you don t need to manage or maintain the key. The disadvantage is that you can t use a configuration file encrypted in this way on any other computer. With both of these options, encryption is completely transparent. When you retrieve a setting from an encrypted section, ASP.NET automatically performs the decryption and returns the plain text to your code (provided the required key is available). Similarly, if you modify a value programmatically and save it, encryption is performed automatically. However, you won t be able to edit that section of the web.config file by hand. But you can still use WAT, the IIS snap-in, or your own custom code. When you use the configuration API, the decryption and encryption steps are performed automatically when you read from or write to a protected section.

To turn off view state for a single control, set the EnableViewState property of the control to False. To turn off view state for an entire page and all its controls, set the EnableViewState property of the page to False, or use the EnableViewState attribute in the Page directive, as shown here: <%@ Page Language="vb" EnableViewState="False" ... %>

If you profile your database, you ll discover that by binding two controls to the same data source, you cause the query to be executed twice On the other hand, if you bind the page manually, you have the ability to bind the same object to two different controls, which means you need to execute the query only once Clearly, the SqlDataSource imposes a bit of unnecessary extra overhead here, but if you re aware of it you can design accordingly First, you should consider caching, which the SqlDataSource supports natively (see 11 for a full discussion) Second, realize that most of the time you won t be binding more than one control to a data source That s because the rich data controls the GridVew, DetailsView, and FormsView have the ability to present multiple pieces of data in a flexible layout.

To enable encryption programmatically, you need to retrieve the corresponding ConfigurationSection.SectionInformation object and then call the ProtectSection() method. Any existing data is encrypted at this point, and any changes you make from this point on are automatically encrypted. If you want to switch off encryption, you simply use the corresponding UnprotectSection() method.