what is the best way to remove/skip an item from collection object
List<Person> personList = new List<Person>()
personList = dao.GetData(123);
personList = personList.Select(x => x.Comment... ????
resultset:
"GCE"
Not available
"" //comments
"RES"
9.97000000
9.99000000
........
........
........
so, i am targeting the field called "comments" and if the comments are empty then dont render.
i could have do that in foreach
loop with an if condition
but i am looking for the best practice
If you want to destructively remove the offending item from the list then use the RemoveAll(Predicate<T>)
method; it removes every item that matches a predicate from the list:
myList.RemoveAll(x=>x.Comment == whatever);
If you want to keep the list the same and make a filtered sequence of items then use Where
:
foreach(Item item in myList.Where(x=>x.Comment != whatever))
...
That keeps the list the same; the Where
just gives you a "view" of the list that has the filter applied to it.
You can use Where
like...
foreach (var a in personList.where(x => !string.IsNullOrWhitespace(x.Comment))
{
// code
}
This will restrict the list to comments that have a non-null and non-whitespace string:
List<Person> personList = dao.GetData(123);
filteredList = personList.Where(x => !String.IsNullOrWhitespace(x.Comment));
You can use LINQ to filter the collection before you even use it. For starters, this is kind of redundant:
List<Person> personList = new List<Person>()
personList = dao.GetData(123);
personList = personList.Select(x => x.Comment... ????
It sounds like what you're looking for is this:
var personList = dao.GetData(123)
.Where(p => !string.IsNullOrWhitespace(p.Comment))
.Select(p => ...
Then you can loop through the items in personList
.
Of course, looking back, if you don't even need the .Select()
(that is, if it's not doing anything other than an attempt to filter), then this is simpler:
var personList = dao.GetData(123)
.Where(p => !string.IsNullOrWhitespace(p.Comment))
There are two extensions you could care about:
Where
:
var subset = collection.Where(x => x != someValue);
This method simply takes all the elements and applies the predicate to it, yielding only the matching elements.
And Skip
, SkipWhile
:
var skipFirstThreeItems = collection.Skip(3);
var skippedItems = collection.SkipWhile(x => x != "SomeValue")
The important distinction with the second one is that it will skip values until the predicate is matched, and then it will take all subsequent elements.
I often think that the best way is debatable, but I like to be explicit about what the code is doing:
var peopleWithComments = dao.GetData(123)
.Where(person => person.Comment.IsPresent());
...
public static class StringExtensions {
public bool IsPresent(this string self) {
return !String.IsNullOrWhitespace(self);
}
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.