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Validating an XML File using XSD in .NET .2.0


Posted Date: 02-Oct-2007  Last Updated:   Category: .NET Framework    
Author: Member Level: Silver    Points: 7


This article explains the difference in validating an XML file using a schema in .NET 1.1 and .NET2.0



Validating an XML File using XSD in .NET 2.0



Below given is the.NET 1.1 code for validating an XML File using an XSD File.


//.NET1.1 code
///
/// Methode to validate XML File
///
/// This method expects input XML as string
/// Path to schema file
/// true if xml is validated else false
private bool ValidateXmlUsingXsd(string XmlData,String SchemaPath)
{
XmlValidatingReader v = new XmlValidatingReader(XmlData, XmlNodeType.Document, null);
v.ValidationType = ValidationType.Schema;
v.ValidationEventHandler +=
new ValidationEventHandler(MyValidationEventHandler);

while (v.Read())
{
// Can add code here to process the content.
}
v.Close();

return isValid;

}
///
/// This event handler is called only when a validation error occurs
///
///
///
public static void MyValidationEventHandler(object sender,
ValidationEventArgs args)
{
//these two variables should be initialized as class level variables
isValid = false;
errorMessage = "Validation event\n" + args.Message;

}
///
/// Method to get XML in a string from an XML file
///
///
///
private string GetStringFromXML(string fileName)
{
StreamReader rd = new StreamReader(fileName);
string str = rd.ReadToEnd();
rd.Close();
return str;
}




Calling the method :
bool valid = ValidateXmlUsingXsd(str, txtXSD.Text);


There are some changes in the .NET 2.0 code for XML Validation .

XmlValidatingReader is marked as obsolete. Need to use XMLReader.Create() using XmlReaderSettngs instead

There are some behavioral changes between validation using the XmlReaderSettings and XmlSchemaSet classes and validation using the XmlValidatingReader class.

The XmlReaderSettings and XmlSchemaSet classes do not support XML-Data Reduced (XDR) schema validation.

The most important difference I found out is that to do XML data validation using a schema, settings.ValidationFlags = XmlSchemaValidationFlags.ReportValidationWarnings;
Flag must be enabled. Otherwise the Schema check error will not be displayed.


//.NET2.0 code
private bool ValidateXmlUsingXsd2(string XmlData,String SchemaPath)
{
XmlReaderSettings settings = new XmlReaderSettings();
settings.ValidationType = ValidationType.Schema;
settings.Schemas.Add(null, SchemaPath);
settings.ValidationFlags = XmlSchemaValidationFlags.ReportValidationWarnings;
settings.ValidationEventHandler += new ValidationEventHandler(ValidationCallBack);

StringReader xmlStream = new StringReader(XmlData);
XmlReader reader = XmlReader.Create(xmlStream, settings);
while (reader.Read()) ;

return isValid;
}

private static void ValidationCallBack(object sender, ValidationEventArgs e)
{
isValid = false;
errorMessage = "Validation Error: " + e.Message;
}


More about XmlSchemaValidationFlags Enumeration




Member name
Description
AllowXmlAttributes
Allow xml:* attributes even if they are not defined in the schema. The attributes will be validated based on their data type.
None
Do not process identity constraints, inline schemas, schema location hints, or report schema validation warnings.
ProcessIdentityConstraints
Process identity constraints (xs:ID, xs:IDREF, xs:key, xs:keyref, xs:unique) encountered during validation.
ProcessInlineSchema
Process inline schemas encountered during validation.
ProcessSchemaLocation
Process schema location hints (xsi:schemaLocation, xsi:noNamespaceSchemaLocation) encountered during validation.
ReportValidationWarnings
Report schema validation warnings encountered during validation.

In a nutshell, Always set settings.ValidationFlags = XmlSchemaValidationFlags.ReportValidationWarnings; when a schema validation is required for the XML in .NET 2.0


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