public override ExpressionNode VisitUnaryExpression(UnaryExpression expression)
{
// First visit arguments
base.VisitUnaryExpression(expression);
if (expression.Op == UnaryOperator.LogicalNot)
{
// Replace "NOT NOT expr" by "expr"
UnaryExpression unOp = expression.Operand as UnaryExpression;
if (unOp != null)
{
if (unOp.Op == UnaryOperator.LogicalNot)
{
return(VisitExpression(unOp.Operand));
}
}
// Replace "NOT expr IS NULL" and "NOT expr IS NOT NULL" by
// "expr IS NOT NULL" and "expr IS NULL" resp.
IsNullExpression isNull = expression.Operand as IsNullExpression;
if (isNull != null)
{
isNull.Negated = !isNull.Negated;
return(VisitExpression(isNull));
}
// Apply negation on EXISTS
ExistsSubselect existsSubselect = expression.Operand as ExistsSubselect;
if (existsSubselect != null)
{
existsSubselect.Negated = !existsSubselect.Negated;
return(existsSubselect);
}
// Apply negation on ALL/ANY subquery
AllAnySubselect allAnySubselect = expression.Operand as AllAnySubselect;
if (allAnySubselect != null)
{
allAnySubselect.Op = AstUtil.NegateBinaryOp(allAnySubselect.Op);
allAnySubselect.Type = (allAnySubselect.Type == AllAnySubselect.AllAnyType.All) ? AllAnySubselect.AllAnyType.Any : AllAnySubselect.AllAnyType.All;
return(allAnySubselect);
}
// Apply De Morgan's law
BinaryExpression binOp = expression.Operand as BinaryExpression;
if (binOp != null)
{
BinaryOperator negatedOp = AstUtil.NegateBinaryOp(binOp.Op);
if (negatedOp != null)
{
ExpressionNode newLeft;
ExpressionNode newRight;
if (binOp.Op == BinaryOperator.LogicalAnd || binOp.Op == BinaryOperator.LogicalOr)
{
newLeft = new UnaryExpression(expression.Op, binOp.Left);
newRight = new UnaryExpression(expression.Op, binOp.Right);
}
else
{
newLeft = binOp.Left;
newRight = binOp.Right;
}
binOp.Op = negatedOp;
binOp.Left = newLeft;
binOp.Right = newRight;
return(VisitExpression(binOp));
}
}
}
return(expression);
}