private static string getValue(Manager mgr, Document document,
string query, QueryContext context)
{
///////////////////////////////////////////////////////////////////////////
//////// Return specific information from a document. //////////////////
//////// Assumes a result set of size 1 //////////////////
///////////////////////////////////////////////////////////////////////////
using(Value docValue = new Value(document))
{
// Perform the query
// The document provides the context for the query, so neither
// collection() nor doc() needs to be part of the query.
using(QueryExpression queryExpr = mgr.Prepare(null, query, context))
{
using(Results result = queryExpr.Execute(null, docValue, context, new DocumentConfig()))
{
// We require a result set size of 1.
if(!result.MoveNext())
{
System.Console.WriteLine("Error! query '" + query +
"' returned a result size size != 1");
throw new System.Exception( "getValue found result set not equal to 1.");
}
// Get the value. If we allowed the result set to be larger than size 1,
// we would have to loop through the results, processing each as is
// required by our application.
return result.Current.ToString();
}
}
}
}
// Method to add a "description" element after the query's target nodes
private static void doModify(Manager mgr, Container container, QueryContext context,
string query, Transaction txn)
{
using(QueryExpression expression = mgr.Prepare(txn, query, context))
{
System.Console.WriteLine("Updating document for the expression: '" +
query + "' ");
System.Console.WriteLine("Return to continue: ");
System.Console.ReadLine();
// Print the document(s) to be updated -- those that describe
// Zapote Blanco (a fruit). The document strings are only being
// printed to show before/after results.
// Most modification programs would not perform the additional queries.
using(Results results = expression.Execute(txn, context, new DocumentConfig()))
{
dumpDocuments(results);
results.Reset();
System.Console.WriteLine("About to update the document(s) above.");
System.Console.WriteLine("Look for a new element after the target " +
"element, named 'description' ...");
System.Console.WriteLine("Return to continue: ");
System.Console.ReadLine();
// The modification is a new element in the target node, called
// "descripton, which goes immediately after the <product> element.
// if this program is run more than once, and committed, additional
// identical elements are added. It is easy to modify this program
// to change the modification.
using(Modify modify = mgr.CreateModify())
{
using(QueryExpression subexpr = mgr.Prepare(txn, ".", context))
{
modify.AddInsertAfterStep(subexpr, Modify.XmlObject.Element, "description", "very nice");
using(UpdateContext uc = mgr.CreateUpdateContext())
{
long numMod = modify.Execute(txn, results, context, uc);
System.Console.WriteLine("Performed " + numMod + " modification operations");
dumpDocuments(results);
}
}
}
}
}
}