A well-formed document is one which meets the specifications laid down in the XML recommendation - that is, it follows the rules for element and attribute names, contains all essential declarations, and has properly-nested elements.The validation support provided by ASP.NET MVC and Entity Framework Code First is a great example of the DRY principle in action. 1 A valid document also respects the rules. A well-formed document follows the basic syntactic rules of XML, which are the same for all XML documents. Just open it, run and enjoy.XML validation is the process of checking a document written in XML (eXtensible Markup Language) to confirm that it is both well-formed and also 'valid' in that it follows a defined structure. NET project made with Visual Studio 2013.
Csharp Xml Validator How To Perform Validation
In case you don't remember what it looked like, here it is again: Learn everything about this open source databaseThe only major difference in this version of the XML file is the introduction of the "xsi:noNamespaceSchemaLocation" attribute. And then, once you know how to perform validation, you also need to know how to handle validation errors - which is why this article also includes a simple example that uses built-in exception handling mechanisms to trap errors that the Reader may come across.Let's get started! Returning To The LibraryI'll explain how the XMLValidatingReader works by again referring to the sample XML instance created in the first part of this article. If you need to validate your XML file before processing it, you need to know its close cousin, the XmlValidatingReader object, which is derived from the same abstract XMLReader parent class. You see, while the class does throw up errors if your XML document isn't well-formed, it does not support validation against a DTD, XDR or XSD Schema. However, for smaller, simpler documents, a DTD can often be overkill, adding substantially to download and processing time.Now, what does this have to do with the XmlTextReader class I discussed in so much detail in the last segment of this tutorial? Nothing, really. By imposing some structure on an XML document, a DTD makes it possible for documents to conform to some standard rules, and for applications to avoid nasty surprises in the form of incompatible or invalid data.DTDs and XML Schemas are essential when managing a large number of XML documents, as they immediately make it possible to apply a standard set of rules to different documents and thereby demand conformance to a common standard.
Csharp Xml Validator Code Using The
An error occurred at (15, 4).Notice that the error message explicitly highlights the rogue element in the XML file.Now, let's take a closer look at how this code works. An error occurred at (15, 4).Validation Error: The 'inventory' element is not declared. That's why you'll see the following output when you reload the example in the browser: Validating file: Validation Error: The element 'book' has invalid child element 'inventory'. Consider the following ASP.NET code, which validates the XML document instance against the XML Schema above: String strXmlFile = " // initialize the XML readersXmlTextReader objXmlTxtRdr = new XmlTextReader(strXmlFile) XmlValidatingReader objXmlValRdr = new XmlValidatingReader(objXmlTxtRdr) ObjXmlValRdr.ValidationType = ValidationType.Schema ObjXmlValRdr.ValidationEventHandler += new ValidationEventHandler (ValidationMonitor) Output.Text = "Validating file: " + strXmlFile.ToString() + "" Output.Text += "Validation " + (blnValidationSuccess = true ? "successful" : "failed") + "." Void ValidationMonitor (object sender, ValidationEventArgs args)Output.Text += "Validation Error: " + args.Message + "" If you were to test this code using the "library.xml" file shown above, the XML document instance should pass the validation tests with flying colours: Validating file: Validation successful.But look what happens if you add a new, unwanted element to the document instance: The XML Schema definition does not allow the XML author to add this new element.
This is done via the "ValidationType" property of the XmlValidatingReader object: You can set the "ValidationType" property of the XmlValidatingReader object to any one of the following:"ValidationType.None" - no validation is required"ValidationType.Auto" - search for a file automatically if available, carry out validation"ValidationType.DTD" - perform validation using a DTD"ValidationType.XDR" - perform validation using a XDR"ValidationType.Schema" - perform validation using an XML SchemaWhile the validator is checking the XML document against the Schema, it generates an event if it encounters an error. Here, I need to first initialize a plain-vanilla XmlTextReader object, and then pass this object as a parameter to the new XmlValidatingReader object, as shown below: Next, I have defined the mechanism to use when validating the XML - in this case, an XML Schema. This is followed by the definition of the object required for our example.
Of course, in between all the element and attributes are quaint symbols and keywords that will make sense only to DTD experts (if you don't belong to that elite group, you can start with the reference links provided at the end of this article).And to complete this jigsaw, we have the ASP.NET code that uses the XmlValidatingReader object to tst the XML document instance against the DTD, as shown below: ObjXmlValRdr.ValidationType = ValidationType.DTD // only process the elements, ignore everything elseIf(objXmlValRdr.NodeType=XmlNodeType. In such situations, you'll also need to know how you can use a DTD to validate an XML document instance.Here's the updated XML file - notice it now includes a reference to a DTD instead of an XML Schema: This brings us to the actual beast - the "library.dtd" DTD file: A close look at this file and you will see that it describes the structure of the XML document instance fairly well. To DTD Or Not To DTDLegacy is bitter reality and so, while XML Schemas are the way forward as far as validation is concerned, don't be surprised when you come across a DTD or two in the XML framework that you are using. Validation " + (blnValidationSuccess = true ? "successful" : "failed") + "." The example closes with a check on the "blnValidationSuccess" variable, displaying the appropriate outcome of the validation process to the user in the browser. Here, the Read() loop is an empty block because I didn't really want to process the data in the file, just validate it to show you how it was done. In this example, I've defined an event handler function named ValidationMonitor(), and associated it with the object via its "ValidationEventHandler property": Validation Error: " + args.Message + "" Notice how the "Message" property of the object is used to display a user-friendly error message in the browser.Finally, assuming no errors in validation, you can iterate over the document and process the XML inside it with the Read() method I showed you in the previous article.
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