/// <summary>
/// Returns true if this node evaluates to an empty string,
/// otherwise false.
/// It may be cheaper to determine whether an expression will evaluate
/// to empty than to fully evaluate it.
/// Implementations should cache the result so that calls after the first are free.
/// </summary>
internal override bool EvaluatesToEmpty(ConditionEvaluator.IConditionEvaluationState state)
{
if (_cachedExpandedValue == null)
{
if (_expandable)
{
string expandBreakEarly = state.ExpandIntoStringBreakEarly(_value);
if (expandBreakEarly == null)
{
// It broke early: we can't store the value, we just
// know it's non empty
return false;
}
// It didn't break early, the result is accurate,
// so store it so the work isn't done again.
_cachedExpandedValue = expandBreakEarly;
}
else
{
_cachedExpandedValue = _value;
}
}
return (_cachedExpandedValue.Length == 0);
}
