Re: [dotNetRDF-develop] Building sparql query

[Rob V. <rv...@do...>]

Hi Aleksandr

 

You can use the TriplePattern, GraphPattern etc classes to build queries in
theory but much of that part of the API has protected constructors and
methods to stop people building completely invalid queries.  For dynamically
building SPARQL queries I've recently added a SparqlParameterizedString
class to the source in response to a suggestion from another user.  This
allows you to build a SPARQL query from a base string in the style of ADO
e.g.

 

//Assumes you already have a VirtuosoManager in the variable manager

 

SparqlParameterizedString queryString = new SparqlParameterizedString();

queryString.QueryText = "SELECT * WHERE {?subj a @type ; @prop ?value .}";

queryString.SetUri("type", new Uri("http://example.org/myType"));

queryString.SetUri("prop", new Uri("http://example.org/myProperty"));

 

Object results = manager.ExecuteQuery(queryString.ToString());

 

The parameterized string allows you to insert values into a base query
string where the parameters are specified ADO.Net style as @param - there
are SetUri(), SetLiteral() and SetBlankNode() methods to insert values as
well as a SetParameter() method to insert an existing INode instance into
the query.  When you call the ToString() method the values for the
parameters get inserted into the String with the proper formatting such that
the output is a valid SPARQL query string.

 

Would it be helpful to have the ability to insert an entire triple into the
string as this could be added if you needed it?

 

This code was added as of revision 635 and will be part of the next release
(0.2.1) which should hopefully be out in the next week or so.

 

Hope that helps,

Rob Vesse

 

From: Aleksandr A. Zaripov [mailto:za...@tp...] 
Sent: 04 March 2010 03:46
To: dot...@li...
Subject: [dotNetRDF-develop] Building sparql query

 

hi

I'm searching for some way to build a sparql query from some objects and
execute it against Virtuoso. I found TriplePattern, GraphPattern, Filter,
Union etc. in Algebra namespace, but as I understand, there is no way to
convert them into query string?

С уважением, Зарипов Александр
za...@tp...