UserGuide Result Formatting

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Result Formatting

When you make a SPARQL query as detailed on the Querying with SPARQL you typically get back a SparqlResultSet object. While you can trivially dump results to strings using the ToString() method this doesn't give you a particularly pretty output, this page details various methods by which you can format results for display.

Using Formatters

dotNetRDF supports a powerful Formatting API which is discussed in general elsewhere, this can be leveraged for the purposes of formatting results. Since values in each column of a SparqlResult are just normal INode values you can use any of the existing INodeFormatter implementations for this.

For example:

//Assume we already have our query results in the variable results

//Create a formatter
INodeFormatter formatter = new TurtleFormatter();

foreach (SparqlResult result in results)
{
   Console.WriteLine(result.ToString(formatter));
}

The above will print out results using Turtle formatting for the terms, exact formatting will vary depending on the formatter used and arguments passed to the constructor.

Extracting Values as Strings

Sometimes you may prefer to extract the actual values from the nodes as strings e.g.

//Assume we have our results in the variable results

foreach (SparqlResult result in results)
{
  INode n;
  String data;
  if (result.TryGetValue("var", out n))
  {
    switch (n.NodeType)
    {
      case NodeType.Uri:
        data = ((IUriNode)n).Uri.AbsoluteUri;
        break;
      case NodeType.Blank:
        data = ((IBlankNode)n).Label;
        break;
      case NodeType.Literal:
        //You may want to inspect the DataType and Language properties and generate
        //a different string here
        data = ((ILiteralNode)n).Value;
        break;
      default:
        throw new RdfOutputException("Unexpected Node Type");
    }
  }
  else
  {
    data = String.Empty;
  }

  //Do what you want with the extracted string
}