Questions tagged [linq]

Language INtegrated Query (LINQ) is a Microsoft .NET Framework component that adds native data querying capabilities to .NET languages.

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23 views

LINQ query to return LIST<T> subset of data

It's late and this works, but there has to be a better way to write this LINQ query, but I'm not smart enough. I can get it to work with a lambda expression, but I would prefer LINQ. This is my json ...
9
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3answers
187 views

ExactlyOne extension method

I often find in codebases something on the order of if (sprockets.Count() > 0) which is easily replaced with LINQ's ...
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2answers
108 views

PLINQ code analysis in terms of efficiency of cryptographic hashes generation

I have the following code that I wrote in order to find the correct password by generating hashes out of all possible combinations and comparing each of them with the target. I'm trying to make ...
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5answers
512 views

Grouping into more groups in one iteration

I had a need to group the same dataset in several groups. So instead of repeatedly query the dataset, I made an extension that could do it once. The caveat is, that the result is materialized in ...
4
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3answers
182 views

SkipLast of an IEnumerable<T> - Linq Extension

As my answer to this question, I came up with this solution: ...
2
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1answer
115 views

Performance issue with empty lists

Here's my updated version of the problem I posted at Calculating time windows for entities, adding in suggested changes as well as a change I did so that the Reflection is 'cached' in a ...
2
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1answer
51 views

Populating dropdown lists, using SQL vs. using expression trees and reflection

I'm working with a large enterprise SQL Server database with dozens of tables that are used mainly as lookups to populate dropdown lists, etc. These tables all follow the convention of having (table)...
3
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1answer
77 views

Non brute force algorithm for Birthday Chocolate

Problem: https://www.hackerrank.com/challenges/the-birthday-bar/problem Lily has a chocolate bar that she wants to share it with Ron for his birthday. Each of the squares has an integer on it. She ...
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0answers
23 views

Configure multiple application features by common criteria

My FeatureSerivce provides only basic APIs, so it is good in dealing with single features. Like I can configure only one feauture at a time: ...
2
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2answers
38 views

LINQ queries to generate a report on accrued work time on projects

The following code fetches data from a MySql database to generate a simple report on accrued work time on projects. I've been away from Entity Framework for a while and looking at this code you can ...
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2answers
87 views

Poker Hand evaluation

I want to evaluate Poker Hands an wrote the following Code: https://dotnetfiddle.net/mxMvq9 Anything wrong / to imporve? ...
5
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4answers
172 views

Take N elements from List of Lists

I've come with a solution super tricky for a simple requirement. I think I could solve the problem using LinQ, but I'm not seeing it so clearly at all. What's sure, I'm not comfortable with my code. ...
3
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2answers
168 views

Group list into elements with same value

This is my Result class: ...
2
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1answer
67 views

Parse through an XDocument efficiently and match values to matching object

Minimum viable test program: ...
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1answer
63 views

LINQ or Lambda for two foreach query [closed]

I have a Document Name Table in my SQL database and Files in the Content folder. I have two lists: ListOfFileNamesSavedInTheDB and ...
4
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2answers
120 views

Making a list of customers who buy the top N items from a supplier

I have a method that works perfectly well and does what it's supposed to, albeit a little slow (30 - 40 seconds). I would like to be able to speed it up or at least make it more efficient, any ideas ...
3
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1answer
153 views

Logging inside a Linq fluent chain [closed]

I've posted this to Stack Overflow, but someone voted to close as they felt it was opinion based, so I'm bringing it over to Code Review. I have some Linq fluent chains to shape an original ...
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2answers
143 views

Using IQueryable.GroupBy to count related database entities

Given a DbSet<Client> from an Entity Framework 6 DbContext, I need to count the number of related ...
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1answer
482 views

Filtering List data using LINQ [closed]

In this code I have declared myPushData, myPushDataFilterd and myPushDataFilterd2 variables ...
11
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1answer
499 views

Linq for ObservableCollection

Purpose ObservableCollection<T> is not strictly a WPF class, but its intended purpose seems to be for use in WPF. It's the standard implementation of ...
3
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5answers
581 views

Finding Isogram Word

An isogram (also known as a "nonpattern word") is a word or phrase without a repeating letter, however spaces and hyphens are allowed to appear multiple times. The ...
5
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2answers
863 views

Going from IQueryable<IEnumerable<myObj>> to IEnumerable<myObj>

I have a "GetPersonsPerDepartment()" method returning a IQueryable<IEnumerable<Person>> while I'm trying to get a simple ...
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1answer
360 views

Merging two lists into one by dates [closed]

I have two lists of Slots ...
6
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3answers
753 views

Custom implementation of the linq Zip operator for different length lists

Based on my answer I have my implementation of linq Zip operator which operates on different length lists, and loops shortest list. My implementation: ...
-2
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1answer
135 views

Method to populate a dictionary from properties

I have a class with some properties. In the class I have a method that is "collecting" all the properties in a specific instance of the class to a dictionary, with the properties name being the ...
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1answer
519 views

Reuse Select Expression in LINQ

I have three methods to get the user details based on attributes: Find user details by id, Find user details by username, Find user details by email Here is the program class: ...
2
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3answers
131 views

Grouping report data by one of two criteria

I have a report with a group by filter. A stored procedure returns all the data and maps it to IEnumerable<EventListRow>. The code should then group the data ...
2
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2answers
855 views

Get attribute values with LINQ to XML

I'm pulling the values from the following XML based on the attribute name. ...
3
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1answer
71 views

Determining if there is data left after fetching a page of data

I just faced a problem where I needed to know if extra data was present in a given collection after a Take operation took place. Specifically, this is related to ...
0
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1answer
150 views

Sorting table using multiple columns [closed]

I want to sort entries in a given list on Entry column in most efficient way. Here is how my entries look: ...
5
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4answers
770 views

Take a desired string, iterate through objects to see if it exists in a given field and append a number until a unique string is found

I wanted to in the most generic way possible write a method in C# to achieve the following. Take in a string, a set of objects, and a function to access the field of a given object Look at all of the ...
2
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1answer
116 views

Handling related generic type parameters

In answering a question on StackOverflow, it occurred to me that a more generic version of GroupBy for C# that delegated membership in each group to a class could ...
4
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4answers
156 views

Add dash between more than two consecutive numbers and comma between other numbers in array

I have an ordered array of integer values: 10, 11, 12, 13, 15, 16, 19 and I need to write a dash between first and last consecutive values when there are more than two consecutive values (10-13). ...
2
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0answers
173 views

Handler for jQuery DataTable search with filters and pagination

This AjaxCompound is invoked every time when the user types a key for search or click to sort. It contains 1million data 10 distinct rows by compound name. It takes 1.1 minutes and return only 1-5 KB ...
4
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2answers
148 views

EnumerableHelpers: a partial implementation of LINQ for .NET Framework 2.0

Here is a static class with some helper methods for some common LINQ operations on enumerables, built against .NET Framework 2.0. This class is part of the xofz.Core98 library. Edit: a full review ...
4
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1answer
247 views

Find a list of Windows Services by given criteria

My goal is to implement a method, which finds a list of Windows Services that match given set of criteria: SearchString: A search string ...
8
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3answers
159 views

Build clusters from connections (virus propagation)

The scenario is the following: There is a list of persons and places where those persons visit. Each person is connected to a single or multiple places. See the picture below, where O[i] represents ...
5
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1answer
92 views

Algorithm for tagging list of substrings from a list of strings

I have a list of utterances(strings)/corpus as the follows, ...
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3answers
107 views

List mapping of large data set from file

I have a list of items 116 thousand and my mapping function is taking quite some time to process. I am using the file helpers library to write the CSV to disk but its the for each that is taking ...
0
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1answer
625 views

adding properties together from list of objects using LINQ

Looking to see if there is a simpler way to achieve this. I would love if I could keep the return as a one-line LINQ expression. I want to grab the total number of ...
2
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0answers
38 views

Correct Way to Retrieve Header Records With Filtered Detail Records [closed]

I wrote this in LinqPad. It works. The whole point was to retrieve header records, and only include some detail records. I'm looking for possible improvements to this, specifically around the ...
2
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2answers
1k views

Linq IEnumerable extensions for void functions

I found myself wanting to use Linq to map void methods to an IEnumerable to modify all items. The existing Linq methods require a return variable when mapping, since they are based on ...
2
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0answers
98 views

Implementing the IQueryable counterpart method of the IEnumerable method?

I have created this method to simulate SQL's IN operator: ...
5
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3answers
2k views

LINQ method that selects an item based on previous one

my requirement is to implement a way to filter a collection of elements based on a value of previous one. For example to only select a number that is larger than the previous one. I don't currently ...
5
votes
2answers
192 views

Porting functional programming code to Linq

I am very new to C# programming, so for practice I thought I would try to port a simple haskell function over to Linq. From learn you a haskell, there is the following implementation of powerset: <...
5
votes
1answer
81 views

Representing relations between devices when presented with only one-to-many mappings

There are devices that communicate between each other. Already existing in the Legacy codebase is a list of one-to-many mappings between the devices. I have written a function in my backend that ...
0
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1answer
57 views

Data validation for to check required fields are mapped

Can I break the below foreach and IF statements into LINQ expression. Also, performance wise which will be better. Please suggest. ...
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0answers
43 views

Querying a database to find notifications to comments

I have a solution what I think is not the best, and I want to make this not so expensive. I'm using MVC 5 + SignalR (hubs) + EF + UnitOfWork + Generic Repos. I have a table ...
6
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1answer
63 views

Return true from enumerable that calls function unless that function ever returns false

Is there a tighter way to write this code? ...
0
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1answer
682 views

Entity Framework MVC updating db using a repository method [closed]

I have inherited this code from a legacy project, and it is throwing a New transaction is not allowed because there are other threads running in the session. error. Now I know the problem here is ...