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Questions tagged [ilookup]

16 questions
76
votes
3 answers

ILookup vs. IGrouping

I've been having trouble articulating the differences between ILookup and IGrouping, and am curious if I understand it correctly now. LINQ compounded the issue by producing sequences of IGrouping items while also giving me a…
mckamey
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8 answers

Empty ILookup

I have a method that returns an ILookup. In some cases I want to return an empty ILookup as an early exit. What is the best way of constructing an empty ILookup?
Mike Q
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Does .GroupBy() guarantee order in its groupings?

Say I have an (ordered) sequence of animals: Eagle Elephant Tarantula Terrapin Tiger and I group by first letter: Animals.GroupBy(animal => animal.First()) will the elements of the IGroupings in the resulting sequence be in the same order as the…
spender
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2 answers

Is there a way to flatten a .Net ILookup into a List?

Is there a quick way to get a flattened List from an ILookup that was created from the IEnumerable extension? Updated with example List list = new List(); var lookup = list.ToLookup(key => key); list =…
Joomala
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9
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1 answer

LINQ Convert from IGrouping to Lookup

I have two variables of type ILookup. I wanted to use Union or Concat to combine their values and assign the result to a third variable of the same type. Both Union and Concat return IGrouping. It must be dead simple to convert IGrouping to the…
Anna
4
votes
3 answers

Linq: Create empty IGrouping

I would like to create a function using Linq that summarizes an incoming sequence of values. The function should look something like this: IDictionary> Summarize(IEnumerable values) { return values …
brianberns
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4
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1 answer

filter linq lookup based on values

I would like to filter a linq Lookup based on its values: the lookup: ILookup lookup here's what I've got so far which isn't working: IList cityIndexes = GetCityIndexesByNames(cities); lookup = lookup …
user560498
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4
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2 answers

Creating ILookups

I've got an ILookup generated by some complicated expression. Let's say it's a lookup of people by last name. (In our simplistic world model, last names are unique by family) ILookup families; Now I've got two queries I'm interested…
configurator
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1 answer

How can interface IGrouping yield multiple values?

I wonder what point I overlook. IGrouping is used by LINQ GroupBy. Further, the same logic is applied to ILookup, IIRC. Accordingly, they can return multiple values subject to the key specified. However, instead, I would…
snr
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Linq - convert an ILookup into another ILookup

This should be simple, but I can't think of a good way to do it. How do you transform an ILookup into another ILookup? For example, how would you copy/clone an ILookup, producing another ILookup with the same keys and same groups? Here's my lame…
brianberns
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1 answer

Linq Query to get DataContext Entities based on ILookup

If I have an IEnumerable Values, I can write a Linq to Entities query, like so: DataContext.Answers.Where(a => a.Organization == CurrentUser.Organization || Values.Contains(a.QuestionId)) The (Values.Contains(a.QuestionId)) part is what my…
Gunner Barnes
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1 answer

ILookup store item under multiple keys

I have a situation where I have a set of objects, these objects relate to items in a database. We create a local cache of these objects along with indexes to allow fast filtering/searching of the data. The issue I am having is converting the list of…
Neaox
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CSV file transposed to ILookup

A vendor is providing us a csv file nightly. We need to take that csv, pull out some of the columns, then import them into our in-house application. The csv, as we receive it, looks a bit like this: StudentId, GradYear, 2014 Thing1, 2014 Thing2,…
Jazzy
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ILookup and Casting

I got the following objects: class Base { } class A : Base {} class B : Base {} class C : Base {} enum BaseType { A, B, C, } ILookup lookup = GetBaseInformation(); The GetBaseInformation method returns me a list of Base…
Hélder Gonçalves
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5 answers

What's the best way to split a list of strings to match first and last letters?

I have a long list of words in C#, and I want to find all the words within that list that have the same first and last letters and that have a length of between, say, 5 and 7 characters. For example, the list might have: "wasted was washed washing…
user3473853
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