Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

provided way to serialize ADO.NET objects in binary formats. We'll return to this topic inthe section "Custom Binary Serialization," on page 424.The DataSet Object's Embedded API for XMLTable 9-1 presents the DataSet object methods you can use to work with XML, both inreading and in writing. This list represents the DataSet object's internal XML API, whichis at the foundation of the serialization and deserialization processes for the object.Table 9-1: The DataSet Object's Embedded Serialization APIMethodGetXmlGetXmlSchemaReadXmlReadXmlSchemaWriteXmlWriteXmlSchemaDescriptionReturns an XML representation of the data currentlystored in the DataSet object. No schema information isincluded.Returns a string that represents the XML schemainformation for the data currently stored in the object.Populates the DataSet object with the specified XMLdata read from a stream or a file. During the process,schema information is read or inferred from the data.Loads the specified XML schema information into thecurrent DataSet object.Writes out the XML data, and optionally the schema,that represents the DataSet object to a storagemedium—that is, a stream or a file.Writes out a string that represents the XML schemainformation for the DataSet object. Can write to astream or a file.Note that GetXml returns a string that contains XML data. As such, it requires moreoverhead than simply using WriteXml to write XML to a file. You should not use GetXmland GetXmlSchema unless you really need to obtain the DataSet representation orschema as distinct strings for in-memory manipulation. The GetXmlSchema methodreturns the DataSet object's XML Schema Definition (XSD) schema; there is no way toobtain the DataSet object's XML-Data Reduced (XDR) schema.As Table 9-1 shows, when you're working with DataSet and XML, you can managedata and schema information as distinct entities. You can take the XML schema out ofthe object and use it as a string. Alternatively, you could write the schema to a disk fileor load it into an empty DataSet object. Alongside the methods listed in Table 9-1, theDataSet object also features two XML-related properties: Namespace and Prefix.Namespace specifies the XML namespace used to scope XML attributes and elementswhen you read them into a DataSet object. The prefix to alias the namespace is storedin the Prefix property. The namespace can't be set if the DataSet object alreadycontains data.Writing Data as XMLThe contents of a DataSet object can be serialized as XML in two ways that I'll callstateless and stateful. Although these expressions are not common throughout theADO.NET documentation, I believe that they capture the gist of the two XML schemasthat can be used to persist a DataSet object's contents. A stateless representationtakes a snapshot of the current instance of the data and renders it according to aparticular XML schema (defined in Chapter 1 as the ADO.NET normal form). A statefulrepresentation, on the other hand, contains the history of the data in the object and326