LINQ offers an API called LINQ to XML, formally known as XLinq, that provides support for working with XML. This API resides in the System.Xml.Linq namespace, and you need to add a reference to the assembly with the same name to be able to use it. If you installed the Orcas March CTP bits, the assembly can be found in folder C:\\Windows\\Microsoft.NET\\Framework\\v3.5.20209.<\/p>\n
In the namespace you can find classes such as XNode<\/tt>, XElement<\/tt>, XAttribute<\/tt>, XText<\/tt>, etc.<\/p>\n
XElement implements an XML element. It has several constructor. The following snippet constructs an empty element called winner.<\/p>\n
\r\n XElement root = new XElement(\"winner\");\r\n Console.WriteLine(root.ToString());\r\n<\/pre>\nThe output is <\/p>\n
\r\n<winner\/>\r\n<\/pre>\nOverloaded constructor can take additional parameters. If we pass a string:<\/p>\n
\r\nXElement root = new XElement(\"winner\", \"Manchester Utd.\");\r\n<\/pre>\nWe get:<\/p>\n
\r\n<winner>Manchester Utd.<\/winner>\r\n<\/pre>\nWe can also pass an XAttribute<\/tt><\/p>\n
\r\nXElement root = new XElement(\"winner\", \"Manchester Utd.\",\r\n new XAttribute(\"Year\", 1999));\r\n<\/pre>\nOr<\/p>\n
\r\nXElement root = new XElement(\"winner\", new XAttribute(\"Year\", 1999),\r\n \"Manchester Utd.\");\r\n<\/pre>\nIn this case the winner element will have an attribute called Year<\/i> having the value 1999<\/i>, and the text of the element will be Manchester Utd.<\/i>.<\/p>\n
\r\n<winner Year=\"1999\">Manchester Utd.<\/winner>\r\n<\/pre>\nWe can nest the all these to make a hierarchy of xml elements:<\/p>\n
\r\nXElement root = new XElement(\"winners\",\r\n new XElement(\"winner\",\r\n new XElement(\"Name\", \"Barcelona\"),\r\n new XElement(\"Country\", \"Spania\"),\r\n new XElement(\"Year\", 2006)\r\n ),\r\n new XElement(\"winner\",\r\n new XElement(\"Name\", \"Liverpool\"),\r\n new XElement(\"Country\", \"Anglia\"),\r\n new XElement(\"Year\", 2005)\r\n )\r\n );\r\n<\/pre>\nOf course, the XML elements don’t have to be created like that. They can be dynamically created. One way is using methods like Add<\/tt>, AddFirst<\/tt>, RemoveNodes<\/tt>, etc., methods from the XContainer<\/tt> class.<\/p>\n
\r\nIEnumerable<Winner> winners = UCL.GetWinners();\r\nXElement root = new XElement(\"winners\");\r\n\r\nforeach (Winner w in winners)\r\n{\r\n root.Add(new XElement(\"winner\",\r\n new XElement(\"Name\", w.Name),\r\n new XElement(\"Country\", w.Country),\r\n new XElement(\"Year\", w.Year)));\r\n}\r\n<\/pre>\nAnd we can write this to a file with:<\/p>\n
\r\nRoot.Save(\"winners.xml\");\r\n<\/pre>\nHowever, LINQ to XML offers a better way to generate XML content.<\/p>\n
\r\nIEnumerable<Winner> winners = UCL.GetWinners();\r\n\r\nXElement root = new XElement(\"winners\", \r\n from w in winners\r\n select new XElement(\"winner\",\r\n new XElement(\"Name\", w.Name),\r\n new XElement(\"Country\", w.Country),\r\n new XElement(\"Year\", w.Year))); \r\n<\/pre>\nThe result in this case is the same as above.<\/p>\n
XElements has several overloads for saving its content to a file:<\/p>\n
\r\npublic void Save(string fileName);\r\npublic void Save(TextWriter textWriter);\r\npublic void Save(XmlWriter writer);\r\npublic void Save(string fileName, bool preserveWhitespace);\r\npublic void Save(TextWriter textWriter, bool preserveWhitespace);\r\n<\/pre>\nOn the other hand, XElement<\/tt> offers several overloaded static methods for loading content from XML files:<\/p>\n
\r\npublic static XElement Load(string uri);\r\npublic static XElement Load(TextReader textReader);\r\npublic static XElement Load(XmlReader reader);\r\npublic static XElement Load(string uri, bool preserveWhitespace);\r\npublic static XElement Load(TextReader textReader, bool preserveWhitespace);\r\npublic static XElement Parse(string text);\r\npublic static XElement Parse(string text, bool preserveWhitespace);\r\n<\/pre>\nThe following code loads the content of the file winners.xml and prints it in the console.<\/p>\n
\r\nXElement root = XElement.Load(\"winners.xml\");\r\nConsole.WriteLine(root.ToString());\r\n<\/pre>\nConsidering that we have in winners.xml the list of UEL winners, we can load the content of this XML file and create Winner objects:<\/p>\n
\r\nIEnumerable<Winner> winners =\r\n from e in XElement.Load(\"winners.xml\").Elements(\"winner\")\r\n select new Winner\r\n {\r\n Name = (string)e.Element(\"Name\"),\r\n Country = (string)e.Element(\"Country\"),\r\n Year = (int)e.Element(\"Year\")\r\n };\r\n\r\nforeach (Winner w in winners)\r\n{\r\n Console.WriteLine(\"{0} {1}, {2}\", w.Year, w.Name, w.Country);\r\n}\r\n<\/pre>\nXElement.Load()<\/tt> creates an XElement<\/tt> containing all the elements in the file. Elements()<\/tt> returns only the children called winner<\/i> (in our case all the children elements of the root). After that we project Winners created by accessing the children of element “winner” in the XML file. The output is<\/p>\n
\r\n2006 Barcelona, Spania\r\n2005 Liverpool, Anglia\r\n2004 FC Porto, Portugalia\r\n2003 AC Milan, Italia\r\n2002 Real Madrid, Spania\r\n2001 Bayern Munchen, Germania\r\n2000 Real Madrid, Spania\r\n1999 Manchester Utd., Anglia\r\n1998 Real Madrid, Spania\r\n1997 Borussia Dortmund, Germania\r\n1996 Juventus, Italia\r\n1995 AFC Ajax, Olanda\r\n1994 AC Milan, Italia\r\n1993 Olympique de Marseille, Franta\r\n<\/pre>\nNow suppose you want to project only the names of the winners. In this case we could write:<\/p>\n
\r\nvar winners =\r\n from e in XElement.Load(\"winners.xml\").Elements(\"winner\")\r\n select (string)e.Element(\"Name\");\r\n\r\nforeach (var w in winners)\r\n{\r\n Console.WriteLine(\"{0}\", w);\r\n}\r\n<\/pre>\n<\/p>\nThe ouput of the program is:<\/p>\n
\r\nBarcelona\r\nLiverpool\r\nFC Porto\r\nAC Milan\r\nReal Madrid\r\nBayern Munchen\r\nReal Madrid\r\nManchester Utd.\r\nReal Madrid\r\nBorussia Dortmund\r\nJuventus\r\nAFC Ajax\r\nAC Milan\r\nOlympique de Marseille\r\n<\/pre>\nThis output however lists a team multiple times. If we want to have these winners listed only once we could apply the Distinct operator on the result and select the winners only once:<\/p>\n
\r\nvar winners =\r\n from e in XElement.Load(\"winners.xml\").Elements(\"winner\")\r\n select (string)e.Element(\"Name\");\r\n\r\nvar winnersDistinct = Enumerable.Distinct(winners);\r\n\r\nforeach (var w in winnersDistinct)\r\n{\r\n Console.WriteLine(\"{0}\", w);\r\n}\r\n<\/pre>\nThe new output would be<\/p>\n
\r\nBarcelona\r\nLiverpool\r\nFC Porto\r\nAC Milan\r\nReal Madrid\r\nBayern Munchen\r\nManchester Utd.\r\nBorussia Dortmund\r\nJuventus\r\nAFC Ajax\r\nOlympique de Marseille\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"LINQ offers an API called LINQ to XML, formally known as XLinq, that provides support for working with XML. This API resides in the System.Xml.Linq namespace, and you need to add a reference to the assembly with the same name to be able to use it. If you installed the Orcas March CTP bits, the … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_uag_custom_page_level_css":"","advgb_blocks_editor_width":"","advgb_blocks_columns_visual_guide":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[11,14],"tags":[451,328],"class_list":["post-32","post","type-post","status-publish","format-standard","hentry","category-csharp","category-linq","tag-c","tag-linq-2"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t