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

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⋮A configuration section handler is simply a .NET Framework class that parses aparticular XML fragment extracted from the CONFIG file. We'll look at custom sectionhandlers in more detail in Chapter 15.InteroperabilityXML is key to making .NET Framework applications interoperate with each other andwith external applications running on other software and hardware platforms. XMLinteroperability is a sort of blanket term that covers three .NET-specific technologies:XML Web services, remoting, and XML object serialization.By rolling functionality into an XML Web service, you can expose the functionality toany application on the Web that, irrespective of platform, speaks HTTP andunderstands XML. Based on open standards (HTTP and XML, but also SOAP), XMLWeb services are an emerging technology for system interoperation and are supportedby the major players in the IT industry. The .NET Framework provides a specialinfrastructure to build both remote services and proxy-based clients.Actually, in the .NET Framework, an XML Web service is treated as a special case ofan ASP.NET application—one that is saved with a different file extension (.asmx) andaccessible through the SOAP protocol as well as through HTTP GET and POSTcommands. Incoming calls for both .aspx files (ASP.NET pages) and .asmx files areprocessed by the same Internet Information Services (IIS) extension module, whichthen dispatches the request to distinct downstream factory components.In an XML Web service, XML plays its role entirely behind the scenes. It is first used asthe glue for the SOAP payloads that the communicating sides exchange. In addition,XML is used to express the results of a remote, cross-platform call. But what if you writea .NET XML Web service with one method returning, say, an ADO.NET DataSetobject? How can a Java application handle the results? The answer is that the DataSetobject is serialized to XML and then sent back to the client.The .NET Framework provides two types of object serialization: serialization throughformatters and XML serialization. The two live side by side but have differentcharacteristics. XML serialization is the process that converts the public interface of anobject to a particular XML schema. The goal is simplifying the process of dataexchange between components rather than truly serializing objects that will then bedeserialized to living and effective instances.Remoting is the .NET Framework counterpart of the Distributed Component ObjectModel (DCOM) and uses XML to configure both the client and the remote components.In addition, XML is used through SOAP to serialize outbound parameters and inboundreturn values. Remoting is the official .NET Framework API for communicatingapplications, but it works only between .NET peers.XML serialization, remoting, and XML Web services are covered in Part IV—specificallyin Chapter 11, Chapter 12, and Chapter 13.From MSXML to .NET Framework ClassesPrior to the advent of the .NET Framework, managing XML in the Microsoft worldmeant using the COM-based MSXML, now available in version 4.0, SP1. It goes11
without saying that Microsoft is still strongly committed to supporting XML the COMway, although this does not necessarily mean that we are going to have an MSXML 5.0anytime soon. However, MSXML 4.0 represents an excellent parser for the Windowsplatform and has been updated to support W3C final recommendations for the XMLSchema.COM and .NET Framework XML Core ServicesThe first difference between MSXML and .NET Framework XML core classes thatcatches the eye is the fact that while MSXML supports XMLDOM and SAX parsers, the.NET Framework supplies an XMLDOM parser and XML readers and writers. (More onreaders shortly.) This is just the most remarkable example of a common pattern,however. Quite a few key features of MSXML are apparently not supported in the .NETFramework XML core classes, but this hardly results in a loss of programming power.In general, the biggest (and perhaps the only significant) difference between MSXMLand .NET Framework XML classes is that the former represents a set of classes fullyintegrated into an all-encompassing, self-contained framework. Several functionalitiesthat MSXML has to provide on its own come for free in the .NET Framework from othercompartments. If you happen to use a certain MSXML function and you don't find adirect counterpart in the .NET Framework, check out the MSDN documentation beforeyou panic. In the paragraphs that follow, we'll look at a few examples of .NETFramework functionality that provide the equivalent of some MSXML functionality.MSXML supports asynchronous loading and validation while parsing. The .NETFramework XMLDOM parser, centered around the XmlDocument class, does notdirectly provide the same features, but proper use of the resources of the .NETFramework will let you obtain the same final behavior anyway.MSXML also provides for a multithreaded HTTP client (the XmlHttp object) capable ofissuing both synchronous and asynchronous calls to a remote URL. A similar feature iscertainly available in the .NET Framework, but it has nothing to do with XML classes. Ifyou just want your application to act as an HTTP client, use some of the classes in theSystem.Net namespace (for example, HttpWebRequest and HttpWebResponse).In general, if you loved MSXML, you'll love .NET Framework XML classes too. Theoverall programming interface, especially for XMLDOM processing, is similar, althoughthe underlying implementation is radically different, and several methods and propertieshave been renamed.NoteIn MSXML 4.0, Microsoft introduced the same level of support forsome relatively newer XML standards that are found in .NETFramework XML core classes—in particular, XSD, the XML Schemaobject model, and XPath. If you look at MSXML 3.0, however, thedifferences between managed and unmanaged XML processing areclearer.Using MSXML in the .NET FrameworkAs with other COM objects, you can import the MSXML type library within theboundaries of a .NET application. The layer of system code providing for COMimportation in the .NET Framework is the COM Interop Services (CIS). CIS providesaccess to existing COM components in a codeless and seamless way, without requiringmodification of the original component.The CIS consists of two distinct parts: one part makes COM components usable fromwithin .NET applications, and the other part does the opposite—namely, making .NETclasses callable from within a COM component. To incorporate a COM object into a12
Page 2 and 3: Applied XML Programming for Microso
Page 4 and 5: services. Rainer Heller of Siemens
Page 6 and 7: IntroductionIt was about five years
Page 8 and 9: What Do I Need to Use This Book?Mos
Page 10 and 11: Part I: XML Core Classes in the .NE
Page 12 and 13: Related XML StandardsTable 1-1 list
Page 14 and 15: XMLDOM model (memory footprint and
Page 18 and 19: managed application, you must first
Page 20 and 21: Figure 1-1: Streams can be read and
Page 22 and 23: abstraction and explicitly indicate
Page 24 and 25: The XPath Query EngineXPath is a la
Page 26 and 27: Chapter 2: XML ReadersIn the Micros
Page 28 and 29: Table 2-1: Public Properties of the
Page 30 and 31: Table 2-3: Public Methods of the Xm
Page 32 and 33: Table 2-4: Types of Nodes in the Xm
Page 34 and 35: To produce these results, I created
Page 36 and 37: In particular, the XmlConvert class
Page 38 and 39: The method we create to do this is
Page 40 and 41: Consider the following attribute va
Page 42 and 43: An entity reference consists of the
Page 44 and 45: The NameTable ObjectOne of the secr
Page 46 and 47: End ClassByVal type As XmlNodeType)
Page 48 and 49: Fragments and Parser ContextThe con
Page 50 and 51: You can specify other settings for
Page 52 and 53: FullerAndrewSales ManagerLeverlingJ
Page 54 and 55: String[] m_headerValues;tokensbool
Page 56 and 57: get{if(m_readState != ReadState.Int
Page 58 and 59: }public override string this[string
Page 60 and 61: }}return false;The name of the attr
Page 62 and 63: dt.Columns.Add(col);}reader.MoveToE
Page 64 and 65: Readers and XML ReadersTo cap off o
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Chapter 3: XML Data ValidationOverv
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The XmlValidatingReader Programming
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The ValidationEventHandler EventThe
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Figure 3-1: The sample application
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document, no event is fired, but an
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valtype = "Auto.XDR";Figure 3-2 sho
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validator object for further proces
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);This method creates and adds a ne
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public XmlValidatingReader(Stream,
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XML InteroperabilityAs you can see,
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XSDs are more powerful than DTDs, a
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Compared to the DTD schema, this XD
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xmlns:z='#RowsetSchema'>This simple
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Figure 3-7: The XSD type hierarchy.
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Table 3-6: Mapping Between XSD and
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Table 3-7: Top-Level Elements for X
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The next step is to define a new sc
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Creating an XML Schema with Visual
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Figure 3-10: The graphical represen
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Open the XML readerXmlTextReader re
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Define the pattern for the contentX
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ody of the element. It is a simple
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determine the correct sequence and
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The root element can't be successfu
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Francesco Balena's Programming Visu
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}sw.Write(sb.ToString());sw.Close()
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What the XmlWriter Class Can't DoAl
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stream. Some working memory is free
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Table 4-5: Miscellaneous Writing Me
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If you want to get just the default
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else you might need that the writer
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By using the pubid argument (PUBLIC
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Figure 4-3: A dynamically created X
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This command executes normally, but
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"dinoe:isbn-0735618011");This code
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writer.WriteStartElement("element")
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}writer.WriteEndDocument();writer.C
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}}reader.Close();If in this code yo
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Figure 4-8: A PictureBox control di
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NoteThe entire source code for a sa
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Table 4-8: Public Methods of the Xm
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}Writer.WriteStartElement("xml");Wr
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Testing the XmlRecordsetWriter Clas
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Framework type and map each to an e
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}if (i % 2)writer.WriteNode(reader,
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Table 4-9: Methods of the XmlTextRe
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while(rw.Read()){switch(rw.NodeType
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if (m_reader.HasAttributes){// Cons
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Figure 4-14: The code can be used t
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}}rw.Writer.WriteStartElement(rw.Re
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Note The new keyword is C#-specific
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}The net effect of this code is tha
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.NET XML writers only ensure the we
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Part II: XML Data ManipulationChapt
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3JanetLeverlingWhen processed by an
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child elements when processing an X
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through the base class XmlNode. (Se
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Table 5-3: Events of the XmlDocumen
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Both XmlLinkedNode and XmlCharacter
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Figure 5-3: The XmlLinkedNode class
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Working with XML DocumentsTo be ful
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}}{if (n.NodeType == XmlNodeType.El
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While the secondary thread works, t
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Limitations of the XML DOM Eventing
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XML document is often overkill unle
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If you use a namespace, you might r
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Extending the XML DOMAlthough the .
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Table 5-6: Programming Interface of
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file changes, irrespective of the c
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Figure 5-7: The sample application
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Chapter 6: XML Query Language and N
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Figure 6-1: A sample XML tree in wh
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with the forward slash (/). The fol
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How XPointer Uses XPathAn XPointer
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the caller. Using SelectSingleNode
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StringBuilder sb = new StringBuilde
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Figure 6-4: The node set returned b
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A Better Way to Select a Single Nod
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3. Optionally, precompile the XPath
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Table 6-3: Properties of the XPathN
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the type. In addition, attributes a
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As you can see, several methods hav
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Setting Namespace InformationThe in
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string strX = (string) x;string str
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the navigator's author must careful
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⋮Notice that the sample file syst
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Table 6-10: Properties of the XPath
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supplies the underlying means to id
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• XSL Formatting Objects (XSL-FO)
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HTML," on page 299. In the meantime
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Table 7-2: XSLT Instructions for Da
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Table 7-4: XSLT Instructions for La
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In the first template, the context
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……⋮The expected target schema
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By the way, note that the version a
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The XslTransform ClassNow that we'v
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To avoid threading risks, be aware
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index of the style sheet contents.
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Table 7-7: Transform Method Overloa
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XSLT Output RecordsThe output of th
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Perform the transformation, record
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method, other attributes of interes
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Table 7-8: Methods of the XsltArgum
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the object's DataSetName property.
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s:rowbaseAfter you create the node
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features than the XslTransform clas
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Don't confuse the Internet Explorer
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Supported languages are C#, Visual
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double CalculateSubTotal(XPathNodeI
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profitable, because XML is a metala
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Chapter 8: XML and DatabasesOvervie
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Framework applications. SQLXML 3.0
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......The FOR XML AUTO mode always
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Figure 8-1: The client-side XML for
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lastname AS [Employee!1!Name]This s
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sql:field="FirstName" type="xsd:str
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to instantiate a COM object, query
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}// Process elementswhile(reader.Re
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(No context information specified)X
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}...The base class is for the most
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public override void Close(){m_data
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Synchronizing with a DataSet Object
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denote insertions, deletions, and u
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schema information to associate the
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This schema first defines a relatio
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that throughout the Updategram. The
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object for XML-driven updates, an A
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Table 8-2: Properties of the SqlXml
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Table 8-4: Methods of the SqlXmlCom
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This schema addresses a layout such
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database. If all goes well, the Dat
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Chapter 9: ADO.NET XML Data Seriali
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provided way to serialize ADO.NET o
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1DavolioNancy⋮106897⋮Basically,
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The element describes the body of
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Serializing to Valid XMLAs you can
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Table 9-3: The MappingType Enumerat
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⋮This syntax is simple and effect
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By using keyref and nested types, y
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Figure 9-6: An application that pas
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{}DataTable dt = CreateTempTable(dv
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dt = (DataTable) bf.Deserialize(sr.
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more valuable, because it automatic
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Loading DataSet Objects from XMLThe
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The XML source is read one node aft
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Figure 9-10: ReadXml correctly reco
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Figure 9-12: How Microsoft Visual S
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The reader tracks the current node
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}m_currentAttributeIndex = -1;When
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persistence, resort to the DiffGram
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......The root node can have up to
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object's tables. The data written o
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different blocks. Attributes in the
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If no match is found, ReadXml deduc
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Although this solution is clearly n
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The diffgr:error attribute on the r
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{}// Url is a form property that po
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...By design, the current DiffGram
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a DiffGram. To make DiffGrams reall
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Figure 10-8: The sample save-and-re
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dv.RowStateFilter = DataViewRowStat
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in the RowError property of the cor
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however, the verbosity of XML paten
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Chapter 11: XML SerializationOvervi
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0As you can see, the class represen
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ead-only properties; does not handl
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}public Employee(){m_ID = -1;}publi
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Methods of the XmlSerializer ClassT
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ns.Add("d", "urn:dino-e-xml");ns.Ad
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When designing classes destined to
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eferenced assembly and its properti
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The preceding code creates an attri
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}public string FirstName;public str
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XML as the type dictates. The attri
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create the XmlSerializer object. Ho
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command, the data flows into the se
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XmlAttributes changesFirstName = ne
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{if (emp.Territories == null)emp.Te
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{// Import type mapping information
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As you can see, the first file crea
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A good source for learning about SO
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NoteSome programmers believe that .
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involved, you must use Web services
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handled by .NET Remoting; the user
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Figure 12-3: How .NET Remoting mars
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If you want to play with the transp
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The query involves three tables—E
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As we saw in Chapter 4, the XmlText
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{// Propertiesprotected SalesDataPr
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We'll look more closely at channels
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server only when the client calls a
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Figure 12-5: The IIS application ma
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this little requirement is enough t
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typeof(ServiceSalesProvider),"tcp:/
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}The code in boldface demonstrates
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BinaryWriter writer = new BinaryWri
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Chapter 13: XML Web ServicesOvervie
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intSOAP is not magic—it is a simp
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public class MyWebService : WebServ
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effectively exposed over the Web, a
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Format of SOAP Messages for a Web M
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The SoapRpcMethod AttributeThe RPC
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If you compare this code with the r
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Figure 13-5: Processing a Web servi
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The machine.config file is an XML f
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Namespace="xmlnet/cs/0735618011")]p
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In situations in which the URL can'
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Const TheYear = 1997' Create the HT
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implementation does make a lot of s
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Mobile code allows you to send C# o
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Chapter 14: XML on the ClientOvervi
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accessible XML parser to consume th
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The following code shows a version
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NoteIn general, you can name the ou
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To create a hidden field, you can u
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To load assemblies from directories
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{}int size = 130;this.Columns.Add(m
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private void PrepareSortedDataView(
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Figure 14-3: An ASP.NET page that c
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var parser = new ActiveXObject("Mic
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"SERVER=localhost;DATABASE=northwin
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Chapter 15: .NET Framework Applicat
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Because we're focusing on applicati
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executable, ASP.NET application or
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NoteUser applications don't need to
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The myfile.config file contains the
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Some internal variablesXmlNodeList
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scratch or inherit from an existing
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Table 15-2: Predefined Section Hand
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The interface includes a single met
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NameValueCollection coll;coll = Con
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}if (configMenu != null)AddMenuTool
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}}menuTools.MenuItems.Add(index, mn
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Implementing the DataSet Section Ha
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AfterwordOverviewWhile writing this
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not an application-specific object.
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