[dotNetRDF-Support] SPARQL

[Jostinah L. <89...@gm...>]

Hello dotnetrdf,

I have already create an owl file and i'm planning to integrate the owl
file into C#. i use the code below:
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
          IGraph g = new Graph();
          g.LoadFromFile("exData\\PregnancyInducedHypertension.owl");
            try
            {
                Object results = g.ExecuteQuery("SELECT ?NamedDisease WHERE
{ ?s a ?NamedDisease}");
                if (results is SparqlResultSet)
                {
                    //SELECT/ASK queries give a SparqlResultSet
                    SparqlResultSet rset = (SparqlResultSet)results;
                    foreach (SparqlResult r in rset)
                    {
                        textBox1.Text += r.ToString() + "\r\n";
                    }
                }
                else if (results is IGraph)
                {
                    //CONSTRUCT/DESCRIBE queries give a IGraph
                    IGraph resGraph = (IGraph)results;
                    foreach (Triple t in resGraph.Triples)
                    {
                        textBox1.Text += t.ToString() + "\r\n";
                    }
                }
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

When i query the owl file,i only get this result:

?NamedDisease = http://www.w3.org/2002/07/owl#Ontology
?NamedDisease = http://www.w3.org/2002/07/owl#ObjectProperty
?NamedDisease = http://www.w3.org/2002/07/owl#ObjectProperty
?NamedDisease = http://www.w3.org/2002/07/owl#ObjectProperty
?NamedDisease = http://www.w3.org/2002/07/owl#ObjectProperty
?NamedDisease = http://www.w3.org/2002/07/owl#ObjectProperty
?NamedDisease = http://www.w3.org/2002/07/owl#ObjectProperty
?NamedDisease = http://www.w3.org/2002/07/owl#ObjectProperty...........
////////////////////////////////////////////////////////////////////////////////////////////////

What i want from the result is the value of the node.not address like
that.how can i do that?
When i change the a into rdf:type, it show error "The Namespace URI for the
given Prefix 'rdf' is not known by the in-scope NamespaceMapper"
I have already read the answer in Q&A,but i cannot understand what does it
mean.
Do i still have to use prefix as such PREFIX rdf:<
http://www.w3.org/1999/02/22-rdf-syntax-ns#>

Thanks.
Jostinah