visual basic barcode generator garbage Collections and Debugging in .NET

Encoder QR Code JIS X 0510 in .NET garbage Collections and Debugging

The Caching block, like all the other blocks in Enterprise Library, contains extension points that allow you to create custom providers and integrate them with the block. You can also replace the default cache manager if you want to use a different caching mechanism, or modify the source code to otherwise change the behavior of the block. The cache manager is responsible for loading items from a persistent backing store into memory when you instantiate the application block. It also exposes the methods that manipulate the cache. If you want to change the way that the Caching block loads or manages cached items, for example to implement a distributed or specialist caching mechanism, or perform asynchronous or delayed cache loading, you can use the ICacheManager interface and implement the methods and properties it defines. Alternatively, if you just want to use a different backing store or add a new expiration policy, you can create custom backing store providers and expiration policies and use these instead of the built-in providers and policies. To create a custom backing store provider, you can implement the IBackingStore interface or inherit from the Base BackingStore abstract class. To create a custom expiration policy, you can implement the ICacheItemExpiration interface and, optionally, the ICacheItemRefreshAction interface for a class that refreshes an expired cache item. For more information about extending the Caching block, see the online documentation and the help files installed with Enterprise Library.

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In this chapter: Defining Exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466 Exception-Handling Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 The System.Exception Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474 FCL-Defined Exception Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 Throwing an Exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480 Defining Your Own Exception Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 Trading Reliability for Productivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 Guidelines and Best Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 Unhandled Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 Debugging Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 Exception-Handling Performance Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 506 Constrained Execution Regions (CERs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 Code Contracts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512

DECLARE @TrackingContext VARBINARY(128); DECLARE @UserDetails XML; SET @UserDetails = (SELECT USER_NAME() AS UserName FOR XML RAW('User')); SET @TrackingContext = CAST(@UserDetails AS VARBINARY(MAX)); WITH CHANGE_TRACKING_CONTEXT(@TrackingContext) UPDATE HR.Employees SET titleofcourtesy = 'Mr.' WHERE firstname = 'John' AND lastname = 'Chen'; GO

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In both the SQL and OLE Data Provider implementations, if the data type of the column value doesn't match the method used to retrieve it, an InvalidCastException is thrown; no data conversion is attempted. The DBDemo.ListPeople method demonstrates the use of an IDataReader to display the contents of a result set by using various methods to access the returned data fields.