protected override Expression VisitBinary(BinaryExpression node)
{
Expression result = base.VisitBinary(node);
node = result as BinaryExpression;
if (node == null)
{
return(result);
}
switch (node.NodeType)
{
case ExpressionType.Equal:
if (node.Right.IsConstantNullOrEmpty())
{
return(Expression.Not(LdapExpressionFactory.Present(node.Left)));
}
if (node.Right.NodeType == (ExpressionType)LdapExpressionType.Substring)
{
SubstringExpression substring = node.Right as SubstringExpression;
/* If it's a substring expression with no parts to it, it's of one of the following forms:
* X=*. X=*.* X=.* X=.
* (where the dot represents the empty parts list).
* In the first three cases, this translates to Present(X) expression;
* in the last one, to Not(Present(X)). */
if (substring.Parts.Count == 0)
{
if (substring.WildcardAtStart || substring.WildcardAtEnd)
{
return(LdapExpressionFactory.Present(node.Left));
}
else
{
return(Expression.Not(LdapExpressionFactory.Present(node.Left)));
}
}
}
break;
}
return(node);
}
protected override Expression VisitBinary(BinaryExpression node)
{
Expression left = this.Visit(node.Left);
Expression right = this.Visit(node.Right);
if (node.NodeType == ExpressionType.Equal &&
left.NodeType == (ExpressionType)LdapExpressionType.Attribute &&
right.NodeType == ExpressionType.Constant
)
{
ConstantExpression constant = (ConstantExpression)right;
if (constant.Value == null)
{
return(Expression.Not(LdapExpressionFactory.Present(left)));
}
}
return(node.Update(left, node.Conversion, right));
}
