How to validate an XML by Schema XSD?

Question

I’m trying to validate the values of a XML through a file XSD. I’m trying it this way:

XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load(xmlReader);
ValidationEventHandler eventHandler = new ValidationEventHandler(ValidationEventHandler);
xmlDoc.Schemas.Add(schemaSet);
xmlDoc.Validate(eventHandler);

static void ValidationEventHandler(object sender, ValidationEventArgs e) 
{
    switch (e.Severity)
    {
        case XmlSeverityType.Error:
          Console.WriteLine("Error: {0}", e.Message);
        break;
        case XmlSeverityType.Warning:
          Console.WriteLine("Warning {0}", e.Message);
        break;
   }
}

But when debugging and executing the xmlDoc.Validate(eventHandler) get the following error:

The 'http://www.w3.org/2000/09/xmldsig#:Signature' element is not declared.

I’ve looked in several places and I can’t solve the problem; How can I solve this problem?

XML