how to set value in list using linq c#

Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. c# - Add items to list from linq var - Stack Overflow Enumerable.Empty()) instead of list. rev2023.5.1.43405. Doing changes must be done in other logic. What you could do, if you don't want to do it the first way and if your collection is a list already (but not an IEnumerable) you can use the ForEach extension method in linq to do what you're asking. All I am doing is creating a working example, as my FYI says.. i'm really caling just the for loop part of it (the rest is just setup) in an area that's different from this. For multiple. An interesting question, but Linq is about querying and what you're doing here doesn't look much like a query to me. Why are players required to record the moves in World Championship Classical games? I just want something more concise that can be used more easily in a delegate without creating a multi-line monster. Folder's list view has different sized fonts in different folders. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. "Signpost" puzzle from Tatham's collection, Simple deform modifier is deforming my object. rev2023.5.1.43405. class - Set the list value using linq - Stack Overflow Find centralized, trusted content and collaborate around the technologies you use most. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? I use a simple list here. Or use (list ?? Making statements based on opinion; back them up with references or personal experience. I found SingleOrDefault to be my answer of choice - same as Single but returns 'null' if it can't find it. Any suggestion? It's not LINQ, and it's not really much different to your nested for loops, just slightly less verbose. MathJax reference. This appears to be a response to another answer rather than an answer to the question. Why are players required to record the moves in World Championship Classical games? And the enumerable containing the objects isn't modified at all. I have attached my sample program. What is Wario dropping at the end of Super Mario Land 2 and why? c# - Find an item in a list by LINQ - Stack Overflow Making statements based on opinion; back them up with references or personal experience. I don't think this would help. I'm using VS 2008. Why is it shorter than a normal address? Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. It doesn't work because Select() doesn't actually iterate through the collection until you enumerate it's results, and it requires an expression that evaluates to a value. Here is an example. What should I follow, if two altimeters show different altitudes? I want to do: Just change all values for a property in all elements of my collection. is there such a thing as "right to be heard"? IEnumerable vs List - What to Use? //d A new List, yes - but containing the same items, which will be updated correctly. You should iterate your list, and modify your values like: foreach (var student in myList) { if (student.Name == "Tom") { student.Marks = 35; } } Or foreach (var student Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Sometimes when modifying properties in a foreach loop, the changes do not remain. All values are updated in one line of code and you browse the List only ONE time. This new list is then discarded. You need change increment to postfix (rankPosition++) or initial value of rankPosition to 0. In my application I have a list of items I need to sort by price and set a rank/position index for each item. Think about a typical Linq2SQL query where you query data and then update the values. The property value is not changed. (from c in listOfCompany where c.id == 1 select c).First ().Name = "Whatever Name"; For Multiple updates. rev2023.5.1.43405. The only difference between them is that the .First method will throw an exception if there is no such object in the collection when the second one returns the It's not them. User without create permission can create a custom object from Managed package using Custom Rest API. A boy can regenerate, so demons eat him for years. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, No offense, but this seems like using Linq for the sole purpose of using linq, not because it's actually solving a problem (as a matter of fact, it's created a problem), I may be wrong, but I thought there is no, How a top-ranked engineering school reimagined CS curriculum (Ep. rev2023.5.1.43405. and MatchingColumnName1 and MatchingColumnName2 are properties of collections. Be aware that it only updates the first company it found with company id 1. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. What is the best way to give a C# auto-property an initial value? See below for arguments against it. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Why did DOS-based Windows require HIMEM.SYS to boot? Why refined oil is cheaper than cold press oil? How do I stop the Flickering on Mode 13h? my code gives error can you please tell how i do this. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? This article shows the three ways in which you can write a LINQ query in C#: Use query syntax. How to set a value in one list when comparing it with other list Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You can remove the .ToList call. this would be used for thing done to each date time as opposed to thing done with each date time That would be slightly different. Should I re-do this cinched PEX connection? Very useful. true : false, Searches for the specified object and returns the index of the first occurrence within the list, Note that it returns -1 if the value doesn't occur in the list, This will help you in getting the first or default value in your LINQ List search. Generating points along line with specifying the origin of point generation in QGIS. How do I clone a list so that it doesn't change unexpectedly after assignment? You can create a extension method: public static IEnumerable Do(this IEnumerable self, Action action) { To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Find centralized, trusted content and collaborate around the technologies you use most. Can anyone help me with a working expression? Since you save your result to a new List anyway, you can just Select the result instead: Oh and % wont do you any good here anyway, your number would be converted to int first, if it works at all. (Your question does not sound like you want to copy the original objects). If you make your expression return a value, and add something that will fully evaluate the query, such as ToList(), to the end, then it will "work", ie: That being said, ToList() has some disadvantages - mainly, it's doing a lot of extra work (to create a List) that's not needed, which adds a large cost. c# - Set values with a Linq-Query? - Stack Overflow c# - assign value using linq - Stack Overflow Certainly, the nested for loop works, and I can certainly place it in a function (which I have already done). If it really is a List you don't need LINQ, just use: If you are looking for the item itself, try: bool insertOrderNew = lOrders.Find(r => r == "1234") == null ? { But,in my case, I must repeat the foreach in many collections, and I didn't want to repeat the loop. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? That's all it does. What is the symbol (which looks similar to an equals sign) called? For the sake of the example, T in this case is an object similar to the following: Is there a way I can make this more efficient? The OP since updated the question and having it makes no more sense at all since it's true 100% of the time. Embedded hyperlinks in a thesis or research paper. int index = mylist.FindIndex (p => p.id == 1); if (index<0) { mylist.Add (car3); } else { mylist [index] = car3; } This just uses the existing FindIndex to 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Be aware that it only updates the first company it found with company id 1. For multiple (from c in listOfCompany where c.id == 1 select c).First( Most of these methods (First, Single, Any, ) cannot be. This should work Of course you can write your own ForEach extension for IEnumerable but I remember I had side-effect with it. Not the answer you're looking for? Your code is O(n m), where n is the length of a and m is the length of b. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Not the answer you're looking for? Which reverse polarity protection is better and why? Folder's list view has different sized fonts in different folders. To learn more, see our tips on writing great answers. What differentiates living as mere roommates from living in a marriage-like relationship? Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? Use MathJax to format equations. When do you use in the accusative case? What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Why refined oil is cheaper than cold press oil? How would you do a "not in" query with LINQ? I'm querying to return every element of a List, so I can then set those values. Eric Lippert wrote a great blog post about the subject that is worth a read: "foreach" vs "ForEach". Weighted sum of two random variables ranked by first order stochastic dominance. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. What is Wario dropping at the end of Super Mario Land 2 and why? If you want to create a new List with each element set to a value, you can do this: var changes = Enumerable.Range (0, width) .Select (x => I didn't know either Single() or SingleOrDefault(). Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Using LINQ to remove elements from a List, How to use LINQ to select object with minimum or maximum property value. Making statements based on opinion; back them up with references or personal experience. How can I control PNP and NPN transistors together from one pin? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, There is no ForEach for IEnumerable. Can my creature spell be countered if I cast a split second spell after it? Weighted sum of two random variables ranked by first order stochastic dominance. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 10 : (tl.name == "marks" ? Note that this will throw if the item doesn't exist. A boy can regenerate, so demons eat him for years. Set operations (C#) | Microsoft Learn 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How are engines numbered on Starship and Super Heavy? This assumes that there are only 3 types of name. Asking for help, clarification, or responding to other answers. How is this any different? No symbols have been loaded for this document." // Next, when I try to add vnlist to vendlist, I get an error as I cannot add this to the list I get and error saying I have some invalid arguments. How do I get the number of elements in a list (length of a list) in Python? What are the advantages of running a power tool on 240 V vs 120 V? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. There are a few ways (note that this is not a complete list). c# - Select Multiple Fields from List in Linq - Stack Overflow I've tried using ForEach and various forms of select, etc.. nothing seems to work right. Certainly, foreach is the right way. Update all objects in a collection using LINQ - Stack Overflow Web3. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. At the moment I am doing it like this: You could do it using the let keyword. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? Even if there is a solution out there, I'm not sure I'd use Linq for something like this. I really don't understand why you say it's not meant for this. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Generic Doubly-Linked-Lists C implementation. Parabolic, suborbital and ballistic trajectories all follow elliptic paths. create enumerables over existing collections. Connect and share knowledge within a single location that is structured and easy to search. The list IS updated as expected. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? Was Aristarchus the first to propose heliocentrism? So, finally, I have found an 'inermediate' solution, the 'foreach' method, just similar to the 'Select': Anyway may be it's not as clear as the more simple: First off, this is not a good idea. Can my creature spell be countered if I cast a split second spell after it? It was designed to bring native data querying to .NET. For multiple. How can I get the index of an item in a list in a single step? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. When new changes occure, then those elements get a new DateTime. List1 and List2 are two collections. Not the answer you're looking for? If we need to find an element from the list, then we can use the Find and FindAll extensions method, but there is a slight difference between them. How a top-ranked engineering school reimagined CS curriculum (Ep. Why is it shorter than a normal address? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I don't have a C# compiler here but maybe AddRange instead of Add works: Not the answer you're looking for? Use a combination of query syntax and method from c in listOfCompany where c.id == 1 select c => The code looks like this: For the life of me, I can't seem to figure this one out. Why don't we use the 7805 for car phone chargers? When changes are cleared, I need to reset the times to MinValue. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Weighted sum of two random variables ranked by first order stochastic dominance. This search will find the first or default value, which it will return. 1. Is a downhill scooter lighter than a downhill MTB with same performance? Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? It only takes a minute to sign up. There's not a single query in LINQ that modifies the queried collection (hence "query"). Are there any canonical examples of the Prime Directive being broken that aren't shown on screen? How do I make a flat list out of a list of lists? I just want to get a taste of LINQ searching from enumeration case. Can these methods be used with other collections too like, @yellavon these are extension methods on any type that implements. "Signpost" puzzle from Tatham's collection. What should I follow, if two altimeters show different altitudes? c# - conditional Updating a list using LINQ - Stack Overflow Canadian of Polish descent travel to Poland with Canadian passport. It can be done this way as well foreach (Company company in listofCompany.Where(d => d.Id = 1)).ToList()) What were the most popular text editors for MS-DOS in the 1980s? If you want to create a new List with each element set to a value, you can do this: If you really want to do it using ForEach/LINQ, it's possible to abuse Select (but I don't recommend it): Can you describe some use cases of how you propose to use the said delegate? The list may be a class with several properties and some are used for search. Boolean algebra of the lattice of subspaces of a vector space? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. (Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement). By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. If you want the index of the element, this will do it: You can't get rid of the lambda in the first pass. rev2023.5.1.43405. If I understand you correctly you have to enumerate your nested array for several different reasons and would like to encapsulate that functionality to be reused.. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. He also rips off an arm to use as a sword, Identify blue/translucent jelly-like animal on beach, Ubuntu won't accept my choice of password. foreach(var item in self) { Reme. Avoiding it would require enumerating the collection: Again, I wouldn't recommend this. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? What does 'They're at four. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. When to use .First and when to use .FirstOrDefault with LINQ? Do you want the item in the list or the actual item itself (would assume the item itself). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. When to use .First and when to use .FirstOrDefault with LINQ? But then, at this point, you're better off (with less typing) doing it the "clear" way: This is shorter, very clear in its intent, and very clean. List If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, That's great. LINQ stands for Language Integrated Query. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI, Moving List View items from one list to another, Best way of updating a list of unique items, Find items in a table that match a set of conditions in another table, Multiple similar manager classes for handling scroll lists, Recursive search on Node Tree with Linq and Queue, Collecting data into objects and POSTing to 3rd Party API, Python scripts that generate valid ngrams for use in pseudoword generation. c# - how to query LIST using linq - Stack Overflow To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What is the difference between Python's list methods append and extend? > var boys = new List {"Harry", "Ron", "Neville"}; > boys.IndexOf ("Neville") 2 > boys [2] == "Neville" True This will help you in getting the first or default value in your LINQ List search This search will find the first or default value, which it will return. How can I control PNP and NPN transistors together from one pin? 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Besides, the LINQ equivalent probably wouldn't be any less verbose than my example above. I am using below linq query to set value of SecKey, but I still see the old value in list studentData, below id the sample I am It's better to operate on List. Use LINQ to get items in one List<>, that are not in another List<>. I have my doubts that my box is 18,000 times faster than yours, so something else must be at work here. Was Aristarchus the first to propose heliocentrism? Short story about swapping bodies as a job; the person who hires the main character misuses his body. Connect and share knowledge within a single location that is structured and easy to search. What are the advantages of running a power tool on 240 V vs 120 V? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How can I control PNP and NPN transistors together from one pin? correctionQoutas is a custom object that has four properties. When do you use in the accusative case? I'm trying this but can't get it right: It wouldn't be at all difficult to write a LINQ "query" with side-effects to do what Mystere Man requires, but (a) it would be a dirty hack, and (b) it would probably require as much code as an equivalent, cleaner, non-LINQ solution. Set list property value using LINQ ForEach. I pass a List a using ref, along with another List b. I need to cycle thru List b, which contains around 200,000 items, and for each item in b, it it matches criteria in a, which contains 100,000 or more items, and update it. When to use .First and when to use .FirstOrDefault with LINQ? Connect and share knowledge within a single location that is structured and easy to search. Without digging into what your actual conversion function is doing. Here I have a simple example to find an item in a list of strings. If you need to transform the elements, then you need to use the Select() LinQ function: This gives you an IEnumerable, to freeze the contents and actually do the evaluation, you can use the ToList() function after the Select() function. How to force Unity Editor/TestRunner to run at full speed when in background? This will help you in getting the first or default value in your Linq List search. Why don't we use the 7805 for car phone chargers? How are engines numbered on Starship and Super Heavy? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Which reverse polarity protection is better and why? AddRange takes an enumerable, and it will enumerate it all on its own. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? However, one potential optimization could be realized in your foreach line as such: This would limit the set brought back to only those members that actually need their ToUpdate set rather than just setting them whether they need to or not. Simply put: what you're doing is, it will create new list which will replace old one, BTW the only LINQ here is. I don't have a C# compiler here but maybe AddRange instead of Add works: Thanks for contributing an answer to Stack Overflow! Extract values from HttpContext.User.Claims, Ultrawingrid - Select row based on unique value, Concat all strings inside a List using LINQ, Using LINQ to remove elements from a List. 1. Find centralized, trusted content and collaborate around the technologies you use most. So any LINQ way to search like "from .. in where select", Nah, sorry. There are several different ways to accomplish but here is one using linq and one with out this would allow you to reuse this and do different things to each item. At this point, the Select option is far uglier, more typing, etc.
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how to set value in list using linq c# 2023