Mapping SQL Data to Class Properties

摘要

AS DISCUSSED IN LAST month's column, the XML serialization process generates an XML representation of the data stored in a. NET Framework class. Only the public fields of the class are taken into account and the whole process aborts if the class holds circular references with other managed classes. The Xml Seri al izer class is the. NET Framework tool that governs the process. You use this class to serialize a living instance of a class to a persistence medium and to recreate an object from a source. Last month, I briefly hinted at a bunch of events. You can take advantage of them during the deserialization step whenever the input stream contains an XML document that doesn't match the schema of the object being deserialized. The programmer can fix things up and programmatically map the unmatched XML node to a particular combination of fields in the target object using events such as UnknownNode. This technique is often used to deserialize across different versions of the class. For example, Version 1.0 of the application saves a class. Next, Version 2.0 of the application that manages a slightly different version of the class needs to deserialize the bytes. Using this approach, the same data can be easily mapped to new, or simply renamed, fields. Taken to the limit, the feature also proves useful in a more enticing scenario―mapping SQL Server data directly to class instances. In this article, I'll show how to execute a query that returns XML data and map the various nodes to fields of a predefined class. The process should not be read simply as the deserialization of an instance of the same class. More exactly, the technique discussed here represents a way to map, in total or in part, any XML document stored in a database to any class usable within a. NET application.