private void Validate(string path)
{
XmlValidatingReader valReader = null;
try
{
valReader = new XmlValueLengthValidatingReader(new StreamReader(path));
valReader.ValidationType = ValidationType.Schema;
// to validate according to schema, not defined in xml file
valReader.Schemas.Add(this.Schema);

//Set the validation event handler.
valReader.ValidationEventHandler += new ValidationEventHandler
(ValidationCallBack);
while (valReader.Read())
{
}
}
catch (XmlException e)
{
   // not wellformed
}
finally
{
if (valReader != null)
valReader.Close();
}
}

private void ValidationCallBack (object sender, ValidationEventArgs args)
{
// not valid according to schema
}

Something like this?

Brecht

Or, ofcourse:

<rootelement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="xxx.xsd">
</rootelement>