The DataSet object represents in-memory tables and relations from one or more data sources. The DataSet provides a temporary work area or virtual scratch pad for manipulating data. ADO.NET applications manipulate tables in memory, not within the physical database. The DataSet provides additional flexibility over direct connections to physical databases. Much like a typical cursor object supported by many database systems, the DataSet can contain multiple DataTables, which are representations of tables or views from any number of data sources. The DataSet works in an asynchronous, non-connected mode, passing update commands by way of the Provider to the data source at a later time.
Delphi 8 for .NET provides two kinds of DataSets for your use: standard DataSets and typed DataSets. A standard DataSet is the default DataSet that you get when you define a DataSet object implicitly. This type of DataSet is constructed based on the layout of the columns in your data source, as they are returned at runtime based on your Select statement.
Typed DataSets provide you more control over the layout of the data you retrieve from a data source. A typed DataSet derives from a DataSet class. The typed DataSet lets you access tables and columns by name rather than by way of collection methods. The typed DataSet feature provides better readability, improved code completion capabilities, and data type enforcement unavailable with standard DataSets. The compiler checks for type mismatches of typed DataSet elements at compile-time rather than runtime. When you create a typed dataset, you will see that some new objects are created for you and are accessible by way of the Project Manager. You will notice two files named after your dataset. One file is an XML .xsd file and the other is a code file, in the language you are using. All of the data about your dataset, including the table and column data from the database connection, is stored in the .xsd file. The program code file is created based on the XML in the .xsd file. If you want to change the structure of the typed dataset, you can change items in the .xsd file. When you recompile, the program code file is regenerated based on the modified XML.
For more information about DataSets, see the Microsoft .NET Framework SDK.
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