How to analyze Visual Basic dynamic data driver

This article introduces you how to analyze Visual Basic dynamic data driver, the content is very detailed, interested friends can refer to, hope to be helpful to you.

Visual Basic applications often use advanced ActiveX components to connect to data sources. These data sources may include the use of data access objects (DAO), remote data objects (RDO), OLE DB providers such as ActiveX data objects (ADO), COM data providers, Crystal data objects (CDO) and Crystal data source type libraries, or Visual Basic data controls. Using Crystal reports' Visual Basic dynamic data driver, you can have your applications use these same ActiveX data sources. Visual Basic dynamic data drivers include:

◆ Crystal Reports database driver for Microsoft Data Access Objects (crdb_dao.dll).

◆ Crystal Reports database driver for ODBC (crdb_odbc.dll) for RDO.

◆ Crystal Reports database driver for Microsoft ActiveX Data Objects (crbd_ado.dll).

◆ Crystal Reports database driver for COM data provider (crdb_com.dll).

◆ Crystal Data Object COM DLL (Com32.dll).

◆ Crystal Reports database driver for Crystal Data Object (crdb_cdo.dll).

To learn more about using RDO,DAO and ADO, please refer to Microsoft's documentation. For information about data controls, see your Visual Basic documentation. For information about CDO, see Crystal data objects. For information about crystal type libraries for data sources, see Crystal data Source Type Libraries.

Sometimes, when you may also need to create a data source for a report, it is not actually available at design time. Highly dynamic data may only be available at run time. In this case, the field definition driver (crdb_fielddef.dll) supports data definition files, these file tab-delimited text files that define the fields of the data source, but not the actual data.

In general, Visual Basic dynamic data driver development uses the report designer component to access one or more report files that are designed in advance and save energy at run time. This process requires programmers to be able to obtain data at design time, and the application, when installed, also installs any database drivers and file requirements to ensure that reports can connect to the required data.

The way to connect to the runtime is to save the data in the report file. The data is beautifully packaged and existing reports when required from your custom application. However, disk space is wasted due to the increase in the size of the report file due to the preservation of report data. In addition, the technology produces static report files in which data cannot be updated without a connection to the database.

The field definition driver allows you to create report files that do not specify an actual data source at design time. Instead, the report is based on a data definition file, a placeholder ASCII text file, a representative of the database field. At run time, you add code to your application as the actual source of report data.

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