Comparing Case Insensitive strings in a List of Objects with a Hash

Question

I have a list of strings like this:

    List<string> excelList = new List<string>();
    excelList.Add("ZArA");  excelList.Add("CalviN"); excelList.Add("BaD ZAra");

And I create a Hashset from it like this:

var hashet = new HashSet<string>(excelList,StringComparer.OrdinalIgnoreCase);

And then I have a list of objects of a class like this:

public class MyDbObjects
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int ID { get; set; }
}

List<MyDbObjects> dbObjectses = new List<MyDbObjects>();

// call .add here to add some actual objects to it.

Ok now I want to make sure that ALL the string values in the excelList are existent in my class objects list of dbObjectses as a FirstName or LastName and DON'T CARE ABOUT CASE SENSITIVITY . My code below works BUT it does NOT handle case sensitivity. How do I add that to it?

    var allofThemExist = dbObjectses.All(x => hashet.Contains(x.FirstName) || hashet.Contains(x.LastName));

I think your code doesn't match the text? You said "all string values in excelList exist in your class objects", but you check that all the values in your class objects exist in excelList — canton7, Apr 03 '19 at 14:10
Did you see [this](https://stackoverflow.com/questions/16922435/make-hashsetstring-case-insensitive)? — mm8, Apr 03 '19 at 14:14
Maybe you can use `.Any(y=> string.Equals(y, x.FirstName, StringComparer.OrdinalIgnoreCase))` instead of `.Contains` and the same for `LastName` — IMujagic, Apr 03 '19 at 14:15
Why do you think your code doesn't handle case sensitivity? The `HashSet`'s comparer is case insensitive, so its `.Contains` method will be case insensitive. — ProgrammingLlama, Apr 03 '19 at 14:15
@Andy I don't think this is a duplicate of the linked question. He already has a `HashSet` which uses `StringComparer.OrdinalIgnorecase`. — canton7, Apr 03 '19 at 14:15
@canton7 yep, I applied what I could from those other links ... but now stuck in the case sensitive part... not a duplicate. — Bohn, Apr 03 '19 at 14:17
@Bohn I'm with John - I don't think the problem is where you think it is. If you post a [mcve], we can investigate for ourselves. — canton7, Apr 03 '19 at 14:18
By the way [the case insensitivity works great](https://rextester.com/JYU69930). — ProgrammingLlama, Apr 03 '19 at 14:20

Magnus · Accepted Answer · 2019-04-03T14:30:43.527

2

This should do it:

var hasAll = !excelList.Except(
                dbObjectses.Select(x => x.FirstName).Concat(
                dbObjectses.Select(x => x.LastName)), 
              StringComparer.OrdinalIgnoreCase).Any();

Except uses hashtables internally so should have good performance.

edited Apr 03 '19 at 14:30

answered Apr 03 '19 at 14:23

Magnus

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would this handle edge cases if for example LastName property on one of the objects is NULL too ? – Bohn Apr 03 '19 at 14:24
I would imagine that null would only equate with null. – Robert Harvey Apr 03 '19 at 14:26
@Bohn If excelList contains a null value it will require a null value to be in either FirstName or LastName in dbObjectses – Magnus Apr 03 '19 at 14:29
@Magnus sorry I meant if NULL is in dbObjectses properties ... just to make sure it won't crash – Bohn Apr 03 '19 at 14:30
@Bohn It wont. But if I were you I would test it ;-) – Magnus Apr 03 '19 at 14:31

score 1 · Answer 2 · edited Apr 03 '19 at 14:24

1

instrad of hasset, use the excelList,

var allofThemExist = dbObjectses.All(x => excelList.Contains(x.FirstName) || excelList.Contains(x.LastName));

edited Apr 03 '19 at 14:24

Robert Harvey

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answered Apr 03 '19 at 14:24

Uzair Ahmed

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nop, we want the REVERSE logic. Making sure whatever is in excel list, also exists in dbOjects list – Bohn Apr 03 '19 at 14:29
@Bohn it's almost like your faulty logic was the problem, and not the case sensitivity of the HashSet. Then again you said you ran the code and that's how you know the HashSet the problem, so I assume Uzair's logic is fine since you've decided it's the HashSet. – ProgrammingLlama Apr 03 '19 at 14:31

Comparing Case Insensitive strings in a List of Objects with a Hash

2 Answers2