{"id":104103,"date":"2024-01-29T13:47:32","date_gmt":"2024-01-29T12:47:32","guid":{"rendered":"https:\/\/code-maze.com\/?p=104103"},"modified":"2024-01-31T15:51:18","modified_gmt":"2024-01-31T14:51:18","slug":"csharp-reading-xml-documents","status":"publish","type":"post","link":"https:\/\/code-maze.com\/csharp-reading-xml-documents\/","title":{"rendered":"How to Read XML Documents in C#"},"content":{"rendered":"

In this article, we’ll talk about how to read XML Documents in C#. In the preceding article<\/a>, we addressed the creation of custom XML documents.<\/p>\n

Also, we have already explored how to serialize and deserialize objects to and from XML in the articles titled Serializing Objects to XML in C#<\/a> and\u00a0XML Deserialization in C#<\/a>. So what else can we learn?<\/p>\n

To download the source code for this article, you can visit our GitHub repository<\/a>.<\/div>\n

Reading XML Documents<\/h2>\n

NOTE: The code will employ the classes Person<\/code>, People<\/code>, and CreateXMLUsingXmlWriter<\/code>, developed in the preceding article<\/a>, and we won’t duplicate the code here.<\/em><\/p>\n

Similar to creating XML documents, where we could choose between LinqToXml<\/code> or XmlWriter<\/code>, we once again have two potential approaches: utilizing the XDocument<\/code> class or opting for the older XmlReader<\/code> class.<\/p>\n

The XDocument<\/code> path is simpler and more user-friendly, while XmlReader<\/code> provides greater control over the reading process.<\/p>\n

Using XDocument to Read XML Documents in C#<\/h2>\n

Reading XML using <\/strong>XDocument<\/code> couldn’t be simpler.<\/strong> Whether we are reading XML from a file or a string, the XDocument<\/code> class provides functions for these scenarios.<\/p>\n

To read an XML document from a string, we use the<\/strong> Parse()<\/code> method<\/strong>. To read an XML from a file, we use the <\/strong>Load()<\/code> method<\/strong>.<\/p>\n

If the document is not syntactically correct, these methods will throw an exception:<\/p>\n

public class ReadingXmlUsingXDocument\r\n{\r\n    public XDocument ReadXmlAndCatchErrors(string xml)\r\n    {\r\n        try\r\n        {\r\n            return XDocument.Parse(xml);\r\n        }\r\n        catch (Exception ex)\r\n        {\r\n            Console.WriteLine(\"Something went wrong:\");\r\n            Console.WriteLine(ex);\r\n        }\r\n\r\n        return new XDocument();\r\n    }\r\n}<\/pre>\n
We’ve created a ReadingXmlUsingXDocument<\/code> class utilizing the XDocument<\/code> class. This class features a method, ReadXmlAndCatchErrors()<\/code>, which parses the given XML string. If any errors occur during parsing, the method catches the error, displays it in the console, and returns an empty XDocument.<\/p>\n
To evaluate this method, we can generate XML documents using the previously developed CreateXMLUsingXmlWriter<\/code> class. First, we create a valid XML document and then proceed to read it:<\/p>\n
public static string TestValidXml()\r\n{\r\n    var xmlDoc = ReadXmlAndCatchErrors(CreateXMLUsingXmlWriter.CreateSimpleXML(People.GetOne()));\r\n\r\n    return xmlDoc.ToString();\r\n}<\/pre>\n
Everything unfolds as anticipated. The document is successfully created, and we can both read its content and output it to the console.<\/strong><\/p>\n
But what happens if we provide invalid XML:<\/p>\n
public static string TestInvalidXml()\r\n{\r\n    var xmlDoc = ReadXmlAndCatchErrors(CreateXMLUsingXmlWriter.CreateWrongXML(People.GetOne()));\r\n\r\n    return xmlDoc.ToString();\r\n}<\/pre>\n
XDocument.Parse()<\/code> will throw an exception and our<\/strong> ReadXmlAndCatchErrors()<\/code> method catches it and returns an empty XDocument.<\/strong><\/p>\n
Getting Values From XDocument<\/h2>\n
With the XML document now within the XDocument<\/code> object, the question arises: How do we extract the name or age of a person from the XDocument object?<\/strong><\/p>\n
As this extends beyond the scope of this article, we will briefly outline a few options using the initially created ‘people document’:<\/p>\n
<person>\r\n  <name>\r\n    <firstName>Emma<\/firstName>\r\n    <lastName>Brown<\/lastName>\r\n  <\/name>\r\n  <email>emma.brown@code-maze.com<\/email>\r\n  <age>58<\/age>\r\n<\/person><\/pre>\n
XML document contains data about a person. Among them are the email and the age of the person we want to extract.<\/p>\n
Reading With the Use of the Element Collection<\/h3>\n
Every element inside XDocument<\/code> has an element collection of all its children<\/strong>. If an element has no children, this collection will be empty.<\/p>\n
We traverse through the XML tree by referencing the elements by name and then read their values:<\/p>\n
public static string TestReadWithElementCollection()\r\n{\r\n    var xmlDoc = ReadXmlAndCatchErrors(CreateXMLUsingXmlWriter.CreateSimpleXML(People.GetOne()));\r\n    var name = xmlDoc.Root!.Element(\"name\")!.Element(\"firstName\")!.Value;\r\n    var age = xmlDoc.Root!.Element(\"age\")!.Value;\r\n\r\n    return $\"Name: {name}, Age: {age}\";\r\n}<\/pre>\n
We start from the root of the document, which is a <person><\/code> element. There we search for the <name><\/code> element, and inside the <name><\/code> element, we find the <firstName><\/code> element. From the <firstName><\/code> element, we take the value, which is, of course, the name of the person.<\/p>\n
The same is true for the age.<\/p>\n
Notice that here we are using the ‘!’ operator, as we know in our example case, that the XML document contains all the elements we are searching for.<\/em><\/p>\n
Using XPath<\/h3>\n
To retrieve data from an XML document, we can also utilize XPath<\/code>. The <\/strong>XPath<\/code> language is quite extensive, but in this article, we will provide a simple example of reading the name and age fields:<\/strong><\/p>\n
public static string TestReadUsingXPath()\r\n{\r\n    var xmlDoc = ReadXmlAndCatchErrors(CreateXMLUsingXmlWriter.CreateSimpleXML(People.GetOne()));\r\n\r\n    var name = xmlDoc.XPathSelectElement(\"\/person\/name\/firstName\")!.Value;\r\n    var age = xmlDoc.XPathSelectElement(\"\/person\/age\")!.Value;\r\n\r\n    return $\"Name: {name}, Age: {age}\";\r\n}<\/pre>\n
In this example, we use <\/strong>XPath<\/code> to locate elements like navigating a file system.<\/strong> For instance, to access the <firstName><\/code> element, we use the path “\/person\/name\/firstName<\/code>.”<\/p>\n
There are various ways to express XPath<\/code> queries, such as:<\/p>\n