/// <summary>
/// Compile and execute an expression supplied as a String, with a given context item, where
/// the expression is expected to return a single item as its result
/// </summary>
/// <param name="expression">A string containing the source text of the XPath expression</param>
/// <param name="contextItem">The context item to be used for evaluation of the XPath expression.
/// May be null, in which case the expression is evaluated without any context item.</param>
/// <returns>If the XPath expression returns a singleton, then the the <c>XdmItem</c>
/// which is the result of evaluating the XPath expression. If the expression returns an empty sequence,
/// then null. If the expression returns a sequence containing more than one item, then the first
/// item in the result.</returns>
/// <exception cref="StaticError">
/// Throws a <c>Saxon.Api.StaticError</c> if there is any static error in the XPath expression.
/// This includes both syntax errors, semantic errors such as references to undeclared functions or
/// variables, and statically-detected type errors.
/// </exception>
/// <exception cref="DynamicError">
/// Throws a <c>Saxon.Api.DynamicError</c> if there is any dynamic error during evaluation of the XPath expression.
/// This includes, for example, referring to the context item if no context item was supplied.
/// </exception>
public XdmItem EvaluateSingle(String expression, XdmItem contextItem)
{
XPathSelector xs = Compile(expression).Load();
if (contextItem != null)
{
xs.ContextItem = contextItem;
}
return(xs.EvaluateSingle());
}
private static int Saxon(XPathSelector sel)
{
var l = new List<int>();
for (int i = 0; i < numIters; ++i)
{
var result = sel.Evaluate();
l.Add(result.OfType<XdmValue>().Count());
}
return l.FirstOrDefault();
}