C#中使用XPath的XPathNavigator类移动选择XML数据

XPathNavigator类包含移动和选择XML所需元素的所有方法。
1.创建：
a.如果是从XPathDocument中创建，则是只读的，只能浏览数据；
b.如果是从XmlDocument中创建，则可以编辑文档；
2.查询：使用Select()方法通过XPath语句查询；
3.迭代：使用XPathNodeIterator类，MoveNext()方法移动下一个节点；Current属性表示当前节点；
4.求值：使用Evaluate()方法计算表达式的值；
5.插入节点：先检查CanEdit属性是否为true，再使用InsertAfter()方法插入新节点。

实例：查询和编辑books.xml

01. using System;

02. using System.Collections.Generic;

03. using System.Text;

04. using System.Xml.XPath;

05. using System.Xml;

06.

07. namespace Magci.Test.XML.TestXPath

08. {

09. class Program

10. {

11. private static XPathDocumentdoc;

12. private static XPathNavigatornav;

13.

14. static void Main( string []args)

15. {

16. doc= new XPathDocument(@ "..\..\books.xml" );

17. nav=((IXPathNavigable)doc).CreateNavigator();

18. SearchByGenre( "nove" );

19. TotalPrice();

20. Insert();

21. Console.ReadLine();

22. }

23.

24. public static void SearchByGenre( string search)

25. {

26. //查询bookstore的子元素book中genre属性值为novel的所有节点

27. XPathNodeIteratoriter=nav.Select( "/bookstore/book[@genre='" +search+ "l']" );

28.

29. Console.WriteLine( "\nSearchByGenre:\n" );

30. while (iter.MoveNext())

31. {

32. //迭代所有子代节点

33. XPathNodeIteratornewIter=iter.Current.SelectDescendants(XPathNodeType.Element, false );

34. while (newIter.MoveNext())

35. {

36. Console.WriteLine(newIter.Current.Name+ ":" +newIter.Current.Value);

37. }

38. }

39. }

40.

41. public static void TotalPrice()

42. {

43. XPathNodeIteratoriter=nav.Select( "/bookstore/book" );

44. Console.WriteLine( "\nTotalPrice:\n" );

45. while (iter.MoveNext())

46. {

47. XPathNodeIteratornewIter=iter.Current.SelectDescendants(XPathNodeType.Element, false );

48. while (newIter.MoveNext())

49. {

50. if (newIter.Current.Name== "price" )

51. {

52. Console.WriteLine(newIter.Current.Name+ ":" +newIter.Current.Value);

53. }

54. }

55. }

56. //统计图书总价

57. Console.WriteLine( "Totalprice={0}" ,nav.Evaluate( "sum(bookstore/book/price)" ));

58. }

59.

60. //插入节点

61. public static void Insert()

62. {

63. XmlDocumentdoc= new XmlDocument();

64. doc.Load(@ "..\..\books.xml" );

65. XPathNavigatornav2=doc.CreateNavigator();

66. //判断是否可编辑

67. if (nav2.CanEdit)

68. {

69. XPathNodeIteratoriter=nav2.Select( "bookstore/book/price" );

70. while (iter.MoveNext())

71. {

72. //在当前节点之后插入新节点

73. iter.Current.InsertAfter( "<disc>5</disc>" );

74. }

75. }

76. doc.Save(@ "..\..\newBooks.xml" );

77. Console.WriteLine( "\nnewBooks.xmlsavedsuccessful.\n" );

78. }

79. }

80. }

book.xml:

01. <? xml version = "1.0" encoding = "utf-8" ?>

02. < bookstore >

03. < book genre = "autobiography" publicationdate = "1991" ISBN = "1-861003-11-0" >

04. < title >TheAutobiographyofBenjaminFranklin</ title >

05. < author >

06. < first-name >Benjamin</ first-name >

07. < last-name >Franklin</ last-name >

08. </ author >

09. < price >8.99</ price >

10. </ book >

11. < book genre = "novel" publicationdate = "1967" ISBN = "0-201-63361-2" >

12. < title >TheConfidenceMan</ title >

13. < author >

14. < first-name >Herman</ first-name >

15. < last-name >Melville</ last-name >

16. </ author >

17. < price >11.99</ price >

18. </ book >

19. < book genre = "philosophy" publicationdate = "1991" ISBN = "1-861001-57-6" >

20. < title >TheGorgias</ title >

21. < author >

22. < name >Plato</ name >

23. </ author >

24. < price >9.99</ price >

25. </ book >

26. </ bookstore >

newBooks.xml:编辑后的文档

01. <? xml version = "1.0" encoding = "utf-8" ?>

02. < bookstore >

03. < book genre = "autobiography" publicationdate = "1991" ISBN = "1-861003-11-0" >

04. < title >TheAutobiographyofBenjaminFranklin</ title >

05. < author >

06. < first-name >Benjamin</ first-name >

07. < last-name >Franklin</ last-name >

08. </ author >

09. < price >8.99</ price >

10. < disc >5</ disc >

11. </ book >

12. < book genre = "novel" publicationdate = "1967" ISBN = "0-201-63361-2" >

13. < title >TheConfidenceMan</ title >

14. < author >

15. < first-name >Herman</ first-name >

16. < last-name >Melville</ last-name >

17. </ author >

18. < price >11.99</ price >

19. < disc >5</ disc >

20. </ book >

21. < book genre = "philosophy" publicationdate = "1991" ISBN = "1-861001-57-6" >

22. < title >TheGorgias</ title >

23. < author >

24. < name >Plato</ name >

25. </ author >

26. < price >9.99</ price >

27. < disc >5</ disc >

28. </ book >

29. </ bookstore >