public static HashSet <ColumnExpression> Gather(Expression expression)
{
var visitor = new ReferencedColumnGatherer();
visitor.Visit(expression);
return(visitor.columns);
}
protected override Expression VisitSelect(SelectExpression select)
{
var saveColumns = this.columns;
this.columns = ReferencedColumnGatherer.Gather(select).ToLookup(c => c.Alias);
var saveLastJoin = this.lastJoin;
this.lastJoin = null;
var result = base.VisitSelect(select);
this.columns = saveColumns;
this.lastJoin = saveLastJoin;
return(result);
}