linq query to find duplicates in list c#

Haha, +1 for innovation :) Not only that, this gives exactly what the OP wants. How to check the duplicates or no duplicates using LINQ or Loop in C#? Do US citizens need a reason to enter the US? how to get duplicate items from a list in vb.net, How to get required collection in my LINQ, linq to xml check for duplicates, any equals. Thanks for contributing an answer to Stack Overflow! I've tested you code in LINQPad using the following program: void Main() { var duplicationList = new List { new TestObject("1", "2"), new TestObject("3", "4"), new TestObject("1", "6") }; var dups = duplicationList.GroupBy(x => x).Where(y => y.Count() > 1).Select(y => y.Key); dups.Dump("Duplicate dump: " + dups.Count()); } public class TestObject { public TestObject(string s1, string s2) { String1 = s1; String2 = s2; IsDuplicate = false; } public string String1; public string String2; public bool IsDuplicate; } It doesn't work. How to get duplicate items from a list using LINQ? @RehanKhan: IsMultiple is NOT doing a Count(), it stops Immediately after 2 items. I wrote this extension method based off @Lee's response to the OP. Both examples only return booleans which is not what the OP asked. ForEach : Set the HasDuplicates property. So I want to know if objectA.String1 == objectB.String1, or ObjectA.String2 == ObjectB.String2, or ObjectA.String1 == ObjectB.String", or ObjectA.String2 == ObjectB.String1. Why is a dedicated compresser more efficient than using bleed air to pressurize the cabin? Complete set of Linq to SQL extensions of Duplicates functions checked in MS SQL Server. Without using .ToList() or IEnumerable. These queries exe C# Linq Find duplicates with multiple group by - Stack WebHow to Count Duplicates in List with LINQ. +5 nice even though I think you are doing it the hard way :). @karen FYI, if you're using this in production code, make sure you get some good amount of tests around it. (Bathroom Shower Ceiling). Please accept my apologies for a stupid mistake. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. var duplicates = list.Where(i => !hash.Add(i)); In the example I want to mark the set with id 10 with output (output5) as the duplicate as such combination of Input and created by already existed before in id 1,2,3 (all of which belong to output1). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Best estimator of the mean of a normal distribution based only on box-plot statistics. How To Remove Duplicates from List Using LINQ - Webdevolution Find out if an enumerable contains any duplicate : var anyDuplicate = enumerable.GroupBy(x => x.Key).Any(g => g.Count() > 1); (Winston's solution is O(n) while this one is O(n)). How to find duplicates in a dynamic list of lists in linq? Is it a concern? May I reveal my identity as an author during peer review? Making statements based on opinion; back them up with references or personal experience. This will return a dictionary, with your element as key, and the number of times it's repeated as value. +5. The easiest way to solve the problem is to group the elements based on their value, and then pick a representative of the group if there are more than one element in the group. To learn more, see our tips on writing great answers. How to find duplicate items based on multiple values using LINQ? Please also confirm for me that I've validly transformed your data in C# code. For all these linq statements the collection is only parsed until the requested items are found. I was trying to solve the same with a list of objects and was having issues because I was trying to repack the list of groups into the original list. This More simple way without use Groups just get the District elements and then iterate over them and check their count in the list if their count is >1 this mean it appear more than 1 item so add it to Repeteditemlist. LINQ provides us with a simple solution for this. Skip(1) is skipping the first item :( Do you know what should I do if I want all items? I created a extention to response to this you could includ it in your projects, I think this return the most case when you search for duplicates in List or Linq. And lastly, if it's a dictionary you are looking for, you can use. I don't see the value of this: you create an IEnumerable of anonymous Types that replicates the structure of the List. How can I do this? Using Count() requires to access the complete collection. Hi, im new to uipath and i am trying to construct a linq query to identify duplicates in a specific column in a datatable then delete both the duplicate and initial Find duplicate with Linq - Daily .NET Tips @Mark Bayers : The resulting list should contain, lst.GroupBy(s => s.ToUpper()).SelectMany(grp => grp.Skip(1)); If you want to do a case insensitive comparison :). You must be a master. Then we By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I prefer to use explicitly declared tuples. C# LINQ find duplicates in List - Stack Overflow Linq query work same as on the set of collection and which make use of count ? Finding out duplicates in the list using LINQ Here's a complete code sample which should work for your case. [linq] C# LINQ find duplicates in List - SyntaxFix Finding out duplicates in the list using LINQ I have the list. I created a extention to response to this you could includ it in your projects, I think this return the most case when you search for duplicates in Immediate execution means that the data source is read and the operation is performed once. Not the answer you're looking for? 1 A a@a.com abc What im supposed to do here is separate the unique items and duplicate items using LINQ, i:e; i need to prepare 2 lists of customers as shown Find out if all 593), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Find centralized, trusted content and collaborate around the technologies you use most. 592), How the Python team is adapting the language for an AI future (Ep. How to find the duplication from the list using either Use LINQ to find duplicated rows (with list of specified columns) I use the code below to get the duplicated rows for 3 columns: String, Date, Money. Distinct : Remove double occurrences of foo from the list. var duplicateItems = list.Duplicates(); You can use Zip() and Aggregate() LINQ methods to find duplicates in a List> (or even List>): I have tested it and it's working fine, unless i was missing the fact that there's more than one instance of text. Is there a way to speak with vermin (spiders specifically)? For example: "Tigers (plural) are a wild animal (singular)". After that, we are just checking the values who have repeated only once means are unique. Enumerable.Distinct Method (System.Linq) | Microsoft Docs, RemoveDuplicatesFromOriginalList | C# Online Compiler | .NET Fiddle, finding duplicates for two columns entries in datatable using LINQ, How to find duplicates from a large data file having ~ 10cr records, I want to find the duplicate char in this line in asc order. Is there a word for when someone stops being talented? Another way is using HashSet : var hash = new HashSet(); At the time of execution, a streaming operator performs its operation on each source element as it is read and yields the element if appropriate. The catch here is that it can give wrong answer if the query is enumerated a second time (to prevent, you have to either clear the set or initialize a new one every time). In LINQ, this translates to: If you want to know how many times the elements are repeated, you can use: This will return a List of an anonymous type, and each element will have the properties Element and Counter, to retrieve the information you need. WebIf you want unique values in your duplicates list: var myhash = new HashSet (); var mylist = new List () {1,1,2,2,3,3,3,4,4,4}; var duplicates = mylist.Where (item => g.Skip(1).Any() might be an improvement over g.Count() > 1. Is this mold/mildew? LINQ: Find Duplicates (advanced example with objects) | C# Online Can a simply connected manifold satisfy ? using System.Data; using System.Linq; namespace CommonExtensions { public static class DataTableExtensions { ///