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Wednesday, March 31, 2010

How to validate xml using xsd?

A lot of times I have come across this question on several forums; and to not avail the google, the question is being asked again and again. If at any point someone might feel they should google, and if google ever planned to re-rank my site to a higher level - then I'd guarantee that following code would work.



I did a reply to a post here on StackOverflow; though my code is pretty old - out of my project code - but as they say, old is gold, so here it goes.

Usage:
XMLValidator val = new XMLValidator();
if (!val.IsValidXml(File.ReadAllText(@"d:\Test2.xml"), @"D:\Test2.xsd"))
   MessageBox.Show(val.Errors);

Code:
public class CXmlValidator
{
    private int nErrors = 0;
    private string strErrorMsg = string.Empty;
    public string Errors { get { return strErrorMsg; } }
    public void ValidationHandler(object sender, ValidationEventArgs args)
    {
        nErrors++;
        strErrorMsg = strErrorMsg + args.Message + "\r\n";
    }

    public bool IsValidXml(string strXml/*xml in text*/, string strXsdLocation /*Xsd location*/)
    {
        bool bStatus = false;
        try
        {
            // Declare local objects
            XmlTextReader xtrReader = new XmlTextReader(strXsdLocation);
            XmlSchemaCollection xcSchemaCollection = new XmlSchemaCollection();
            xcSchemaCollection.Add(null/*add your namespace string*/, xtrReader);//Add multiple schemas if you want.

            XmlValidatingReader vrValidator = new XmlValidatingReader(strXml, XmlNodeType.Document, null);
            vrValidator.Schemas.Add(xcSchemaCollection);

            // Add validation event handler
            vrValidator.ValidationType = ValidationType.Schema;
            vrValidator.ValidationEventHandler += new ValidationEventHandler(ValidationHandler);

            //Actual validation, read conforming the schema.
            while (vrValidator.Read()) ;

            vrValidator.Close();//Cleanup

            //Exception if error.
            if (nErrors > 0) { throw new Exception(strErrorMsg); }
            else { bStatus = true; }//Success
        }
        catch (Exception error) { bStatus = false; }

        return bStatus;
    }
}

Here is a kb that demonstrates the use of several types of validation. This site provides Xml/Schema validation online.

Following is the code using non deprecated methods.
public bool IsValidXmlEx(string strXmlLocation, string strXsdLocation)
{
    bool bStatus = false;
    try
    {
        // Declare local objects
        XmlReaderSettings rs = new XmlReaderSettings();
        rs.ValidationType = ValidationType.Schema;
        rs.ValidationFlags |= XmlSchemaValidationFlags.ProcessSchemaLocation | XmlSchemaValidationFlags.ReportValidationWarnings;
        rs.ValidationEventHandler += new ValidationEventHandler(rs_ValidationEventHandler);
        rs.Schemas.Add(null, XmlReader.Create(strXsdLocation));

        using (XmlReader xmlValidatingReader = XmlReader.Create(strXmlLocation, rs))
        { while (xmlValidatingReader.Read()) { } }

        ////Exception if error.
        if (nErrors > 0) { throw new Exception(strErrorMsg); }
        else { bStatus = true; }//Success
    }
    catch (Exception error) { bStatus = false; }

    return bStatus;
}

void rs_ValidationEventHandler(object sender, ValidationEventArgs e)
{
    if (e.Severity == XmlSeverityType.Warning) strErrorMsg += "WARNING: " + Environment.NewLine;
    else strErrorMsg += "ERROR: " + Environment.NewLine;
    nErrors++;
    strErrorMsg = strErrorMsg + e.Exception.Message + "\r\n";
}


Happy validation!

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