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How can I return a value from .NET IGrouping using a key?

I'm struggling to figure out how to get the Value part of an IGrouping instance.

I have the following:

 IList<IGrouping<string, PurchaseHistory> results = someList.GroupBy(x => x.UserName);

And now I want to iterate over each collection and extract purchase histories for this user (and check if there are any things in the purchase history collection).

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3 answers

how about a nested loop?

 IList<IGrouping<string, PurchaseHistory>> results = someList.GroupBy(x => x.UserName); foreach (IGrouping<string, PurchaseHistory> group in results) { foreach (PurchaseHistory item in group) { CheckforStuff(item); } }

or one loop with linq expression

 IList<IGrouping<string, PurchaseHistory>> results = someList.GroupBy(x => x.UserName); foreach (IGrouping<string, PurchaseHistory> group in results) { bool result = group.Any(item => item.PurchasedOn > someDate); }
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Call..

 IList<IGrouping<string, PurchaseHistory> results = someList .GroupBy(x => x.UserName); .Select(result => (result.Key, result.Any(SomeStuffExists)));

WITH..

 bool SomeStuffExists(PurchaseHistory item) { return .. }

gives tuples in the form ..

  • ("UserNameX", true)
  • ("UserNameY", false)
  • ..
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This is so if you want to iterate over all elements

 foreach (IGrouping<int, YourClass> value in result) { foreach (YourClass obj in value) { //Some Code here } }

And so, if you want to find something by the key

 List<YourClass> obj1 = result.Where(a => a.Key == 12).SingleOrDefault().Where(b=>b.objId.Equals(125)).ToList();

(In this case, the key is considered "int")

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