C# loop through class list but only once for multiple names

Question

I think it can be done with linq but i cant find it on google, as i really done have a idea how to look for this issue.

I have a class list like this:

Public class Data
{
    public string name;
    public int someData;
}
public List<Data> allData = new List<Data>();

The list may contain like 32 items, where somedata is generated but the name is taken of the object that someData belongs to. But there might be multiple enterys by the same name, this is easyer to work with later on then 1 name with a int array.

What im looking for is a way to go tough the intire allData list but only once for each name, so 'bob' might be in there 8 times but i want to look trough it and only visit bob once.

It there a way to do this or do i need to rethink my list, and do use a int array?

And feedback is great!

https://stackoverflow.com/questions/10255121/get-a-list-of-distinct-values-in-list — Mitch Wheat, Aug 28 '17 at 02:11
_"go trough the entire `allData` list but only once for each name, so 'bob' might be in there 8 times but i want to look trough it and only visit bob once."_ - this doesn't make sense. If `"bob"` is in the list 8 times and you got through the list you must visit `"bob"` 8 times. — Enigmativity, Aug 28 '17 at 02:21

Jason W · Accepted Answer · 2017-08-28T02:42:15.793

1

Why not use a dictionary with key for the name and integer array or list:

var allData = new Dictionary<string, List<int>>();
allData["Bob"] = new List<int>() { 1 , 2 , 3 };
var allInts = allData.Values.SelectMany(m => m); // IEnumerable<int>
var intsByName = allData["nameToSelect"]; // List<int>
var availableNames = allData.Keys;

There is no harm in your proposed data structure either:

var allInts = allData
    .Select(m => m.someData); // IEnumerable<int>
var intsByName = allData
    .Where(m => m.name.Equals("nameToSelect"))
    .Select(m => m.someData); // IEnumerable<int>
var availableNames = allData.Select(m => m.name).Distinct();

edited Aug 28 '17 at 02:42

answered Aug 28 '17 at 02:11

Jason W

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I dont know if its "bob", the name is basicly random – ImtehQ Aug 28 '17 at 02:13
Just thinking if you need to find all the integers with the string key, a dictionary would make it easier to organize, access, and expand the list. – Jason W Aug 28 '17 at 02:14
well to give a bit more info, i know know how full the list will be nor do i know what items will go in there, so i dont know the names nor the int data in it, Later on i need to access the all the combined int data, and sometimes i need to get only the int data that matches a name – ImtehQ Aug 28 '17 at 02:16
I put in examples for each of the scenarios you suggested. `SelectMany` in LINQ will get you all the int data combined. Then you can just directly access the matching name by using the dictionary structure. – Jason W Aug 28 '17 at 02:39
Yes that will work but i dont know nameToSelect, i dont know what names are in there – ImtehQ Aug 28 '17 at 02:40
Sure, I added how to get a list of available names if you need to see what is in there. I also made equivalent examples if you wanted to use your proposed data structure. Hope this helps! – Jason W Aug 28 '17 at 02:44
allData["Bob"] = new List() { 1 , 2 , 3 }; Will not work as the class might have been a bad example but theres more then just that int, But i fixed it by just making the int a list of ints and now i can just call it foreach loop on alldata then to get the data from the int another forech loop, i was hoping on a lighter way of doing that with link but i think no matter how i do it its just a design flaw :P – ImtehQ Aug 28 '17 at 02:45

C# loop through class list but only once for multiple names

1 Answers1