Not exactly short, but here goes...

1. Create a new console app, and paste in this code:

using System;
using System.Xml;
using System.Xml.Schema;

namespace XmlTest
{
   class Program
   {
       static void Main(string[] args)
       {
           // Schema and XML file names
           string uriOfSchema = @"d:\test\po.xsd";
           string xmlToValidate = @"d:\test\po.xml";
           
           // Define XmlReader settings
           XmlReaderSettings settings = new XmlReaderSettings();
           settings.CheckCharacters = true;
           settings.CloseInput = true;
           
           // Try reading schema
           try
           {
               settings.Schemas.Add(null, uriOfSchema);
           }
           catch (System.Xml.XmlException e)
           {
               Console.WriteLine("Error in " + e.SourceUri + ": " + e.Message);
               return;

               /* NOTE: If e.Message starts with ', everything before e.Message is
                * strangely removed. */
           }
           
           settings.ValidationType = ValidationType.Schema;
           settings.ValidationFlags |= XmlSchemaValidationFlags.ReportValidationWarnings;
           settings.ValidationEventHandler += new ValidationEventHandler(ValidationCallBack);

           try
           {
               using (XmlReader xmlReader = XmlReader.Create(xmlToValidate, settings))
               {
                   if (xmlReader != null)
                   {
                       while (xmlReader.Read());
                       Console.WriteLine("Validation completed.");
                   }
               }
           }
           catch (Exception e)
           {
               Console.WriteLine(e.Message);
           }
       }

       private static void ValidationCallBack(object sender, ValidationEventArgs args)
       {
           switch (args.Severity)
           {
               case XmlSeverityType.Error:
                   Console.WriteLine("Error: " + args.Message);
                   break;
               case XmlSeverityType.Warning:
                   Console.WriteLine("Warning: " + args.Message);
                   break;
           }
       }  

   }
}

2. Then make a file called po.xsd and paste in this code:

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
 <xs:element name="a" type="xs:string"/
</xs:schema>

(There is an intentional well-formedness error on line 3.)

3. Put this file in a folder of your choice and correct the variable 'uriOfSchema' in the code. You won't need the XML file to run this test.

Gustaf