how to set value in list using linq c#

Which was the first Sci-Fi story to predict obnoxious "robo calls"? from c in listOfCompany where c.id == 1 select c => Asking for help, clarification, or responding to other answers. When new changes occure, then those elements get a new DateTime. I'm not happy yet. 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? Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? The following example depicts the behavior of the Enumerable.Distinctmethod on a I think you try to add a complete list instead of a single CheckItems instance. "Signpost" puzzle from Tatham's collection, Simple deform modifier is deforming my object. If you need to add any IEnumerable collection of elements to the list you need to use AddRange. ), Ubuntu won't accept my choice of password. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Find centralized, trusted content and collaborate around the technologies you use most. Why refined oil is cheaper than cold press oil? { Asking for help, clarification, or responding to other answers. rev2023.5.1.43405. (from c in listOfCompany where c.id == 1 select c).First ().Name = "Whatever Name"; For Multiple updates. 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 Thanks for contributing an answer to Stack Overflow! var list = from something in someList select GetModifiedObject (x); // but change one property private MyType Boolean algebra of the lattice of subspaces of a vector space? 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. Canadian of Polish descent travel to Poland with Canadian passport. Does a password policy with a restriction of repeated characters increase security? I have my doubts that my box is 18,000 times faster than yours, so something else must be at work here. I didn't know either Single() or SingleOrDefault(). In both cases , the update is not done with Linq :). You're trading one assignment for one condition, that shouldn't change much. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? I used to use a Dictionary which is some sort of an indexed list which will give me exactly what I want when I want it. I like this. As sircodesalot mentioned, you can't use linq to do something like that. Connect and share knowledge within a single location that is structured and easy to search. Short story about swapping bodies as a job; the person who hires the main character misuses his body. If we had a video livestream of a clock being sent to Mars, what would we see? Why did US v. Assange skip the court of appeal? Thanks. If you want to avoid this anonymous type here is the And the enumerable containing the objects isn't modified at all. This will help you in getting the first or default value in your Linq List search. Why are players required to record the moves in World Championship Classical games? What are the advantages of running a power tool on 240 V vs 120 V? No symbols have been loaded for this document." and do I need to check if _list is null in the form of from .. in _list? The OP since updated the question and having it makes no more sense at all since it's true 100% of the time. Learn more about Stack Overflow the company, and our products. What are the advantages of running a power tool on 240 V vs 120 V? Is a downhill scooter lighter than a downhill MTB with same performance? ', referring to the nuclear power plant in Ignalina, mean? What is the best way to give a C# auto-property an initial value? Would My Planets Blue Sun Kill Earth-Life? Reme. Most of these methods (First, Single, Any, ) cannot be. Was Aristarchus the first to propose heliocentrism? Enumerable.Empty()) instead of list. How do I split a list into equally-sized chunks? How can I control PNP and NPN transistors together from one pin? Should I re-do this cinched PEX connection? If you want to modify all returned objects, you still have to use a loop to iterate over the objects. Note that this will throw if the item doesn't exist. I just want something more concise that can be used more easily in a delegate without creating a multi-line monster. Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? I'm trying this but can't get it right: 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? 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 should I follow, if two altimeters show different altitudes? It's about querying, i.e. So simply iterate over that enumeration and set the new values: Note that I cut the trailing decimals by simple arithmetic instead of converting the values to strings and back. It should not be hard to analyze the complexity of this. 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. rev2023.5.1.43405. I just want to get a taste of LINQ searching from enumeration case. At the moment I am doing it like this: You could do it using the let keyword. 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. Very useful. Identify blue/translucent jelly-like animal on beach. How do I remedy "The breakpoint will not currently be hit. Code Review Stack Exchange is a question and answer site for peer programmer code reviews. Asking for help, clarification, or responding to other answers. Making statements based on opinion; back them up with references or personal experience. I guess what I'm really saying here is I want a concise way to set all elements of a multi-dimensional array to a given value. 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). If you had a more generic collection IEnumerable, you can use Select in Linq to build a projection where property will be set as desired (original collection will be left untouched!): listOfRequestAssigned .Where (x => x.RequestedNumber == CurrentRequest) .Select (x => { x.RequestCompleted = true; return x; }) WebYou can try LINQ. LINQ is not really intended to be used for updating collections. IEnumerable vs List - What to Use? Not the answer you're looking for? How a top-ranked engineering school reimagined CS curriculum (Ep. What were the most popular text editors for MS-DOS in the 1980s? WebIf you really want to use linq, you can do something like this li= (from tl in li select new Myclass { name = tl.name, age = (tl.name == "di" ? Can you perhaps include some description of your answer instead of just posting a blob of code? Where will return all items which match your criteria, so you may get an IEnumerable with one element: First will return the first item which matches your criteria: Note that FirstOrDefault() will behave the same, except it will return null for reference types, or the default value for value types, instead of throwing an exception. Here is an example. Single will return a single result, but will throw an exception if it finds none or more than one (which may or may not be what you want): Note that SingleOrDefault() will behave the same, except it will return null for reference types, or the default value for value types, instead of throwing an exception. It's exactly what I was looking for, How a top-ranked engineering school reimagined CS curriculum (Ep. C# void QueryHighScores(int exam, int score) { var highScores = from student in students where student.ExamScores [exam] > score select new { Name Besides checking for it's existance with if, first. The code will look something like this. (Your question does not sound like you want to copy the original objects). Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? FYI, I know that DateTime defaults to MinValue, in reality this is clearing the arrays to default after they've already been set. Adding EV Charger (100A) in secondary panel (100A) fed off main (200A), Folder's list view has different sized fonts in different folders. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Why did DOS-based Windows require HIMEM.SYS to boot? Not the answer you're looking for? I've tried using ForEach and various forms of select, etc.. nothing seems to work right. Doing changes must be done in other logic. I disagree, it is in fact a query, but a query with side effects. Eric Lippert wrote a great blog post about the subject that is worth a read: "foreach" vs "ForEach". Find centralized, trusted content and collaborate around the technologies you use most. Or use (list ?? This article shows the three ways in which you can write a LINQ query in C#: Use query syntax. foreach(var item in self) { 1. rev2023.5.1.43405. Connect and share knowledge within a single location that is structured and easy to search. If x.Value has decimals, I want to change that value to take just the first decimal woithout rounding it. 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. I really don't understand why you say it's not meant for this. It's an easy way to filter out nulls. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. What were the most popular text editors for MS-DOS in the 1980s? Is there any known 80-bit collision attack? Asking for help, clarification, or responding to other answers. There's no -1 index (not found) in my example. Folder's list view has different sized fonts in different folders. Set list property value using LINQ ForEach. Connect and share knowledge within a single location that is structured and easy to search. This appears to be a response to another answer rather than an answer to the question. Be aware that it only updates the first company it found with company id 1. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? It's also a violation of the expectations involved with LINQ - LINQ is about querying, which suggests there shouldn't be side effects when using LINQ, and the entire purpose here is to create side effects. it will be discarded but, how will you replace older list values? To learn more, see our tips on writing great answers. Note that you can add a ForEach extension method which performs an action on each object, but I would still recommend avoiding that. 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. Where does the version of Hamapil that is different from the Gemara come from? Can I use LINQ to find an item in the list? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, How to use LINQ to select object with minimum or maximum property value, LINQ: When to use SingleOrDefault vs. FirstOrDefault() with filtering criteria. LINQ is about querying, not for updating collections. rev2023.5.1.43405. 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 I want to do: Just change all values for a property in all elements of my collection. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Even by limiting it like this, it still takes around 3 min. Google "LINQ side effects" for more information. 20 : 30)) See below for arguments against it. What is the symbol (which looks similar to an equals sign) called? Think about a typical Linq2SQL query where you query data and then update the values. my code gives error can you please tell how i do this. To learn more, see our tips on writing great answers. 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. Also, you Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, That's great. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Making statements based on opinion; back them up with references or personal experience. Did the drapes in old theatres actually say "ASBESTOS" on them? Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? 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? However, those are all lamda expression style. Your code is O ( n m ), where n is the length of a and m is the length of b. The below is practically the same as the answer provided by Florian Schmidinger: Thanks for contributing an answer to Stack Overflow! Nevermind, actually you can get rid of the lambdas for a few cases Great answers! What are the advantages of running a power tool on 240 V vs 120 V? This solves the problem by resorting to nullable ints: If you want to count the number of items that match: And don't forget to check the list for null in any of these cases. Where does the version of Hamapil that is different from the Gemara come from? You can create a extension method: public static IEnumerable Do(this IEnumerable self, Action action) { Making statements based on opinion; back them up with references or personal experience. 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 If you simply need to get the elements that are of a certain type, you can do this: That would give the subset that are MyQuota or are directly assignable to that type. Your first example is actually the correct method. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, This question is difficult/dangerous to answer without misleading people into thinking that LINQ is an appropriate solution to your problem. Should I re-do this cinched PEX connection? correctionQoutas is a custom object that has four properties. Asking for help, clarification, or responding to other answers. If you want the index of the element, this will do it: You can't get rid of the lambda in the first pass. foreach(var item in self) { Is there a generic term for these trajectories? Would My Planets Blue Sun Kill Earth-Life? There are a few ways (note that this is not a complete list). He also rips off an arm to use as a sword. using Linq would be: listOfCompany.Where(c=> c.id == 1).FirstOrDefault().Name = "Whatever Name"; 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. Connect and share knowledge within a single location that is structured and easy to search. Connect and share knowledge within a single location that is structured and easy to search. Ubuntu won't accept my choice of password. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I don't really see how this is any different. What does LINQ return when the results are empty, Use LINQ to get items in one List<>, that are not in another List<>. There are certainly ways to (ab)use LINQ to achieve the same results, but I'd consider them to be dirty hacks. Can I use my Coinbase address to receive bitcoin? LINQ stands for Language Integrated Query. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. When do you use in the accusative case? Please read, Updating items of one List that match another List, How a top-ranked engineering school reimagined CS curriculum (Ep. To learn more, see our tips on writing great answers. How can I get the index of an item in a list in a single step? dont forget the return syntax it took me one hour, Very neat! Since you haven't given any indication to what you want, here is a link to 101 LINQ samples that use all the different LINQ methods: 101 LINQ Samples. Connect and share knowledge within a single location that is structured and easy to search. How can I control PNP and NPN transistors together from one pin? WebThis is the best I have right now: var allCountries = repository.GetCountries (); var topitem = allCountries.Single (x => x.id == 592); var finalList = new List (); finalList.Add Not the answer you're looking for? Without digging into what your actual conversion function is doing. 10 : (tl.name == "marks" ? is there such a thing as "right to be heard"? In my application I have a list of items I need to sort by price and set a rank/position index for each item. ex. // 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. Why did DOS-based Windows require HIMEM.SYS to boot? 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. //d You are essentially doing a join and then an update. 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. Making statements based on opinion; back them up with references or personal experience. rev2023.5.1.43405. Which method performs better: .Any() vs .Count() > 0? Not the answer you're looking for? Web14. Use LINQ to get items in one List<>, that are not in another List<>. What is the Efficiency and Performance of LINQ and Lambda Expression in .Net? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The check if you have decimal places is unneccessary too, since the output will be a double anyway. 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. Thanks for contributing an answer to Code Review Stack Exchange! Weighted sum of two random variables ranked by first order stochastic dominance. 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. rev2023.5.1.43405. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. But,in my case, I must repeat the foreach in many collections, and I didn't want to repeat the loop. One thing to note about using SingleOrDefault is that because it throws an exception if more than one match is in the list, it has to iterate through every item, where FirstOrDefault will stop searching once the first match is found. Simply put: what you're doing is, it will create new list which will replace old one, BTW the only LINQ here is. The ToList is making a list, populating it, and the immediately discarding it. Weighted sum of two random variables ranked by first order stochastic dominance. I suspect that this can be written shorter using LINQ over objects syntax. I think your code is perfectly readable and won't improve much if you force it to have lots of lambdas and such. Here is one way to rewrite your method to use LINQ: public static int GetItemIndex(string search) { List _list = new List() { "one", "two", By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Are there any canonical examples of the Prime Directive being broken that aren't shown on screen? So any LINQ way to search like "from .. in where select", Nah, sorry. When to use .First and when to use .FirstOrDefault with LINQ? 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. 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. Sorry, guys. What were the most popular text editors for MS-DOS in the 1980s? You have also a way to set a default value. When to use .First and when to use .FirstOrDefault with LINQ? You could try something like this (not a pure LINQ approach): Here is one way, assuming a class structure as follows: You can join the second list on matching IDs: I think using Join then looping through the list would be more efficient. Not the answer you're looking for? Can I use the spell Immovable Object to create a castle which floats above the clouds? What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? Why did US v. Assange skip the court of appeal? How can I control PNP and NPN transistors together from one pin? Asking for help, clarification, or responding to other answers. Was Aristarchus the first to propose heliocentrism? Do I need to check if list is null first? If you really want to use linq, you can do something like this. Use method syntax. > 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. Not the answer you're looking for? To learn more, see our tips on writing great answers. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? How a top-ranked engineering school reimagined CS curriculum (Ep. The code looks like this: For the life of me, I can't seem to figure this one out. Any suggestion? Using LINQ to change values in collection, How a top-ranked engineering school reimagined CS curriculum (Ep. To learn more, see our tips on writing great answers. This assumes that there are only 3 types of name. Normally I use a for loop or anonymous delegate to do it like this: LINQ is new for me. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Generic Doubly-Linked-Lists C implementation, "Signpost" puzzle from Tatham's collection, Embedded hyperlinks in a thesis or research paper. All values are updated in one line of code and you browse the List only ONE time. Can my creature spell be countered if I cast a split second spell after it? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Here I have a simple example to find an item in a list of strings. Was Aristarchus the first to propose heliocentrism?

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