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Using XML in

XML and API's. . XML is a series of W3C recommendationsFocus on structure and behaviorW3C says very little about API implementationThe only real API defined by the W3C is the Document Object Model (a.k.a DOM)W3C does not mandate any particular API. Relevant W3C Recommendations. Extensible Marku

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Using XML in

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    1. Using XML in .NET Sorting through the choices

    2. XML and API’s

    3. Relevant W3C Recommendations Extensible Markup Language 1.0 Defines syntax Defines document node types Core content represented as Elements, Attributes and Text Non-core content represented as Comments and Processing Instructions

    4. W3C Recommendations (cont.) Namespaces Defines rules for unique element and attribute naming Uniqueness achieved through the use of Uniform Resource Identifiers (URI) All .NET API’s support namespaces

    5. W3C Recommendations (cont.) XML Information Set (Infoset) Defines information items to represent XML node types Abstracts data relationships from syntax Abstracts application from document encoding Content represented to applications as Unicode Most higher level recommendations based on Infoset .NET API’s mostly represent content consistent with the Infoset

    6. W3C Recommendations (cont.) XPath XML Document query language Syntactically similar to directory paths /Invoices/Invoice[descendant::Price > 50] Identify what you want not how to get it Loosely analogous to SQL

    7. Verifying Document Content Wellformed Document conforms to XML 1.0 recommendation All .NET API’s enforce wellformidness Validation Document conforms to defined content rules .NET supported validation types Document Type Definitions, W3C XML Schema, XML Data Reduced Not all .NET API’s support validation

    8. .NET XML API’s Document Object Model (DOM) Implements the W3C DOM recommendation A collection of classes representing the various Infoset information items Indirectly supports validation Relatively resource intensive Only API that both reads & writes Excellent for random access processing Easiest migration if experienced with MSXML’s DomDocument

    9. .NET XML API’s (cont.) XPathNavigator A scrollable, cursor-based document reader Indirectly supports document validation May be more resource efficient then DOM Well-suited for processing document subsets

    10. .NET XML API’s (cont.) XmlReader Abstract (MustOverride) forward-only document reader Well-suited for sequential processing XmlTextReader Derived from XmlReader Absolutely fastest document reader Does not support validation XmlValidatingReader Derived from XmlReader Directly supports validation

    11. .NET XML API’s (cont.) XmlWriter Abstract (MustOverride) forward-only document writer Well-suited for sequential document generation XmlTextWriter Derived from XmlWriter Absolutely fastest document writer Does not support validation

    12. Where’s the SAX Parser? .NET does not provide a SAX parser Benefits of SAX available through XmlReader implementations Microsoft asserts that XmlReader provides several benefits over SAX XmlReader’s “pull” model is simpler to program then SAX’s “push” model Pull model allows program to be optimized for specific document structure Simpler programming when multiple documents processed simultaneously

    13. Document Object Model

    14. Document Object Model (DOM) A hierarchy of classes representing the various document nodes Classes in System.Xml Well-suited for random access and dynamic modification All node classes inherit from XmlNode The only creatable class is XmlDocument Contents validated if populated through XmlValidatingReader

    16. XmlNode XmlNode Abstract (MustOverride) class that generically represents each node Properties & methods to manage node relationships Properties expose node type, name, namespace and content Meaning of name and content vary depending on node type

    17. XmlNode Name & Value Definitions

    18. XmlNode Relationships Relationships managed through read-only XmlNode reference properties OwnerDocument ParentNode Siblings PreviousSibling, NextSibling Children FirstChild, LastChild

    19. DOM Tree Walker

    20. XmlNode Collections Child Nodes childNodes property returnes an XmlNodeList Nodes accessed either through item property or indexer [] XmlNode also exposes an indexer [ ] to access children Invoice[“Price”]

    21. XmlNode Collections (cont.) Attribute Nodes Attributes property returns an XmlAttributeCollection Attributes accessed through an indexer [] by either name or position Attributes added or changed through SetNamedItem method

    22. DOM Tree Walker Using Collections

    23. DOM Tree Walker Using Collections

    24. XPath Support SelectNodes Returns an XmlNodeList containing selection result SelectSingleNode Returns an XmlNode containing only the first node in the selection result

    25. DOM Modification Node Creation New nodes must be created by XmlDocument XmlNode Placement Methods InsertBefore, InserAfter PrependChild, AppendChild RemoveChild, ReplaceChild, RemoveAll Modification events managed through delegates NodeChanging, NodeChanged NodeInserting, NodeInserted NodeRemoving, NodeRemoved

    26. DOM Modification

    27. XPathNavigator

    28. XPathNavigator Classes in System.Xml.XPath Read-only Provides a scrolling cursor “window” over the document Great support for document filtering Best XPath support Content is interpreted according to XPath specification

    29. Creating the Navigator XPathNavigator is an abstract (MustOverride) class Must be factoried from another object Factory objects must implement IXPathNavogable XPathDocument implementation creates an efficient navigator cache Can be populated from XmlValidatingReader XmlNode implementation creates a navigator over the corresponding DOM instance.

    30. XPathNavigator Name & Value Definitions

    31. Cursor Navigation Cursor is controlled by “MoveTo…” methods MoveToRoot MoveToParent MoveToFirstChild Siblings MoveToFirst, MoveToPrevious, MoveToNext Attributes MoveToFirstAttribute, MoveToNextAttribute

    32. Navigator Tree Walker

    33. Navigator Tree Walker

    34. Processing Document Subsets Selection Methods SelectChildren, SelectDescendants, SelectAncestors All functions return an XPathNodeIterator XPathNodeIterator Represents a cursor over the selected set MoveNext method Advances the cursor Current property Returns an XPathNavigator positioned at the current node

    35. XPath Support Select method Generic XPath selection Node set returned as an XPathNodeIterator Evaluate method Returns typed XPath results XPath supports arithmetic operations, logical operations and function calls XPath statements can return numeric, string and Boolean results

    36. Navigator XPath Support

    37. Enhancing XPath Performance XPath statements can be compiled to improve performance XPathNavigator.Compile Compiles XPath string into an XPathExpression XPathExpression represents a compiled XPath statement Select & Evaluate are overloaded to support XPathExpressions in addition to XPath strings

    38. Sequential Reading

    39. XmlReader Abstract (MustOverride) class Represents a forward-only document reader Exposes information only for the current node position NodeType, Name, NamespaceURI, Value Application must handle some lexical issues

    40. XmlReader (cont.) Read method Supports generic document processing Reads the next hierarchical node Application code must manage details of each node Attributes must be specifically read MoveToFirstAttribute, MoveToNextAttribute Iterates through the attribute list MoveToAttribute Move to a named attribute or attribute position

    41. XmlReader (cont.) ReadStartElement & ReadEndElement provide element optimizations Reader verifies that node is an element Overloads support name and namespace verification ReadElementString Encapsulates node type, name & namespace verification Reads element start & end tags and text child Returns value of text child MoveToContent Skips over white space, comments & Processing Instructions

    42. XmlTextReader Derived from XmlReader Most performent .NET XML reader Adds methods to interrogate file information LineNumber, LinePosition, Encoding Adds methods to simplify large data block handling ReadBase64, ReadBinHex, ReadChars

    43. XmlTextReader

    44. XmlValidatingReader Derived from XmlReader Provides DocumentValidation over an existing XmlReader instance Validation errors reported to a delegate or by throwing an exception Delegates registered with ValidationEventHandler If no delegate registered then an XmlException is thrown

    45. XmlValidatingReader XmlDocument and XPathDocument can be populated through XmlValidatingReader

    46. XmlValidatingReader ValidationType & Schemas properties can be used to manage the validation process ReadTypedValue returns value as the proper CLR type Must be using XML Schema or XDR validation

    47. Sequential Writing

    48. XmlWriter Abstract (MustOverride) class Represents a forward-only, sequential document writer Checks wellformidness of generated content Does not validate

    49. XmlWriter (cont.) Provides “Write” methods for the various node types WriteStartElement, WriteEndElement, WriteString, WriteComment, etc. WriteElementString writes start tag, end tag and character child in a single call WriteDocType method supports writing DTD entries WriteRaw method allows pass-through writing of raw XML Writer does not check wellformidness of raw writes

    50. XmlTextWriter Derives from XmlWriter Adds Formatting control Formmatting, Indentation, IndentChar & QuoteChar properties Adds methods to simplify large data block handling WriteBase64, WriteBinHex, WriteChars

    51. XmlTextWriter

    52. Summary Each API is optimized for a different use DOM Random Access, Dynamic Updates XPath Navigator Document Subsets, Rich XPath Support XmlReader Abstract class, models sequential reading XmlTextReader Most performant reader

    53. Summary (cont.) XmlValidatingReader Validation, Usable directly or w/ DOM & XPathDocument XmlWriter Abstract class, models sequential writing XmlTextWriter Most performant writer Often best solution is to use a combination of the API’s

    54. Download & Contact Information Jim Wilson jimw@jwhedgehog.com Presentation Download http://www.jwhedgehog.com/MaineBytes0701 Sample Code Download http://www.jwhedgehog.com/MaineBytes0701

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