/// <summary>
/// 左辺か右辺のいずれかがnullの場合の比較
/// </summary>
private DynamicMetaObject FallbackOnNull(DynamicMetaObject left, DynamicMetaObject right)
{
bool value = this.Operation == ExpressionType.Equal;
Expression restExpr = null;
if (left.Value == null && right.Value == null)
{
restExpr = Expression.And(
BinderHelper.IsNull(left.Expression),
BinderHelper.IsNull(right.Expression));
}
else if (left.Value == null)
{
value ^= true;
restExpr = Expression.AndAlso(
BinderHelper.IsNull(left.Expression),
BinderHelper.IsNotNull(right.Expression));
}
else
{
value ^= true;
restExpr = Expression.AndAlso(
BinderHelper.IsNull(right.Expression),
BinderHelper.IsNotNull(left.Expression));
}
var expr = BinderHelper.Wrap(Expression.Constant(value), this.ReturnType);
var rest = BindingRestrictions.GetExpressionRestriction(restExpr);
return(new DynamicMetaObject(expr, rest));
}
public override DynamicMetaObject FallbackBinaryOperation(DynamicMetaObject left, DynamicMetaObject right, DynamicMetaObject errorSuggestion)
{
Expression expr;
BindingRestrictions rest;
if (left.Value == null)
{
expr = BinderHelper.Wrap(right.Expression, this.ReturnType);
rest = BindingRestrictions.GetExpressionRestriction(BinderHelper.IsNull(left.Expression));
}
else if (left.LimitType == typeof(bool))
{
expr = BinderHelper.Wrap(
Expression.Condition(BinderHelper.Wrap(left.Expression, typeof(bool)), left.Expression, right.Expression),
this.ReturnType);
rest = BindingRestrictions.GetTypeRestriction(left.Expression, typeof(bool));
}
else
{
expr = BinderHelper.Wrap(left.Expression, this.ReturnType);
rest = BindingRestrictions.GetExpressionRestriction(
Expression.AndAlso(
BinderHelper.IsNotNull(left.Expression),
Expression.Not(Expression.TypeIs(left.Expression, typeof(bool)))));
}
return(new DynamicMetaObject(expr, rest));
}
public override DynamicMetaObject FallbackUnaryOperation(DynamicMetaObject target, DynamicMetaObject errorSuggestion)
{
Expression boolExpr;
BindingRestrictions rest;
if (target.Value == null)
{
boolExpr = Expression.Constant(true);
rest = BindingRestrictions.GetExpressionRestriction(BinderHelper.IsNull(target.Expression));
}
else if (target.LimitType == typeof(bool))
{
boolExpr = Expression.Not(BinderHelper.Wrap(target.Expression, typeof(bool)));
rest = BindingRestrictions.GetTypeRestriction(target.Expression, typeof(bool));
}
else
{
boolExpr = Expression.Constant(false);
rest = BindingRestrictions.GetExpressionRestriction(
Expression.AndAlso(
BinderHelper.IsNotNull(target.Expression),
Expression.Not(Expression.TypeIs(target.Expression, typeof(bool)))));
}
var expr = BinderHelper.Wrap(boolExpr, this.ReturnType);
return(new DynamicMetaObject(expr, rest));
}
/// <summary>
/// 左辺、右辺のいずれかがnullで、もう一方はそうでない場合
/// </summary>
private DynamicMetaObject CompareEatherNull(DynamicMetaObject left, DynamicMetaObject right)
{
Contract.Requires <ArgumentException>(
left.Value == null && right.Value != null ||
left.Value != null && right.Value == null);
bool?value = null;
switch (this.Operation)
{
case ExpressionType.LessThan:
case ExpressionType.LessThanOrEqual:
value = false;
break;
case ExpressionType.GreaterThan:
case ExpressionType.GreaterThanOrEqual:
value = true;
break;
}
Expression rest;
bool order;
if (left.Value == null)
{
rest = Expression.AndAlso(
BinderHelper.IsNull(left.Expression),
BinderHelper.IsNotNull(right.Expression));
order = true;
}
else
{
rest = Expression.AndAlso(
BinderHelper.IsNull(right.Expression),
BinderHelper.IsNotNull(left.Expression));
order = false;
}
var expr = BinderHelper.Wrap(Expression.Constant(value ^ order), this.ReturnType);
return(new DynamicMetaObject(expr, BindingRestrictions.GetExpressionRestriction(rest)));
}