XML and JSON 1

XML and JSON

XML and JSON 2

XML, a very brief introduction• XML = eXtensible Markup Language• Language to describe data to be

exchanged on the web• And many other things• Program exchange XML documents• XML documents are processed by programs

• Mark up language• XML tags structure information

• Element• <tag> …. </tag>• An element may have many sub-elements

• Nested elements• An element has exactly 1 super-element

• Except the root element, which has 0 super-elements

• Example XML document<school> <teacher> <name>Anders</name> <city>Roskilde</name> </teacher> <teacher> <name>Michael</name> <city>Valby</name> </teacher></school>

XML and JSON 3

Structure in XML documents

• Well-formed• All start-tags must have a

matching end-tag• <teacher>…</teacher>

• Tags must be properly nested• <school>• <teacher>…</teacher>• </school>

• Only 1 outer tag• Called the root element

• Valid• Well-formed• Conforms to an XML schema

• A set of “grammar rules”• Specifies which tags are allowed, etc.

XML and JSON 4

XML serialization

• A C# object can be serialized into an XML document.• The state of the object is made into an XML document• Class XmlSerializer• Example: XmlSerialization

• An XML object can be de-serialized into a C# object• Create new object using default constructor• Use set part of properties to set the state of the object• Example: XmlSerialization

XML and JSON 5

XPath

• XPath is a language for finding information in an XML document.• With Xpath you can extract the information you need from an XML document

• Examples• http://www.w3schools.com/xml/xml_xpath.asp• xpathExamples, using class XmlDocument

XML and JSON 6

JSON

• JSON = JavaScript Object Notation• Language for storing and exchanging data• Structure• { object }• “name” : “value”• “name” : [“value1”, “value2”]

• Examples• http://www.w3schools.com/json/json_syntax.asp

XML and JSON 7

XML serialization

• A C# object can be serialized into a JSON string• The state on the object is serialized

• A JSON string can be de-serialized into a C# object• Create new object using default constructor• Use set part of properties to set the state of the object

• API• C# has some …• Most C# programmers use JSON.NET from NewtonSoft

• http://www.newtonsoft.com/json• NuGet this package into your Visual Studio solution

• Examples jsonSerialization

XML and JSON 8

XML vs. JSON

• JSON is simpler than XML• JSON string are shorter than XML documents• Use less disk / network bandwidth

• XML came first, then JSON