protected override Expression VisitSubstring(SubstringExpression node)
{
// If any of the clauses that aren't the first or last one are null or empty, remove them.
// If the first or last ones are empty, should alter the expression to add wildcards at those points.
if (node.Parts.Count == 0)
{
// TODO: is this right?
if (!node.WildcardAtStart && !node.WildcardAtEnd)
{
return(Expression.Constant(string.Empty));
}
return(node);
}
if (node.Parts[0].IsConstantNullOrEmpty())
{
return(this.VisitSubstring(node.Update(true, node.Parts.Skip(1), node.WildcardAtEnd)));
}
if (node.Parts.Last().IsConstantNullOrEmpty())
{
return(this.VisitSubstring(node.Update(node.WildcardAtStart, node.Parts.Take(node.Parts.Count - 1), true)));
}
// If there is just one part with no associated wildcards, just use that.
if (node.Parts.Count == 1 && !node.WildcardAtStart && !node.WildcardAtEnd && node.Parts[0].IsConstant())
{
return(node.Parts[0]);
}
// If we get here, we know that neither the first or last part are empty!
var newParts = node.Parts.Where(p => !p.IsConstantNullOrEmpty());
return(node.Update(newParts));
}
protected virtual Expression VisitSubstring(SubstringExpression node)
{
return(node.Update(this.Visit(node.Parts)));
}
