/// <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);
}
/// <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)
{
switch (_value.Length)
{
case 0:
_cachedExpandedValue = String.Empty;
return(true);
// If the length is 1 or 2, it can't possibly be a property, item, or metadata, and it isn't empty.
case 1:
case 2:
_cachedExpandedValue = _value;
return(false);
default:
if (_value[1] != '(' || (_value[0] != '$' && _value[0] != '%' && _value[0] != '@') || _value[_value.Length - 1] != ')')
{
// This isn't just a property, item, or metadata value, and it isn't empty.
return(false);
}
break;
}
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);
}