how to set value in list using linq c#

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 using Linq would be: listOfCompany.Where(c=> c.id == 1).FirstOrDefault().Name = "Whatever Name"; The check if you have decimal places is unneccessary too, since the output will be a double anyway. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Not the answer you're looking for? EDIT: Simply put: what you're doing is, it will create new list which will replace old one, BTW the only LINQ here is. 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 A new List, yes - but containing the same items, which will be updated correctly. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Simple deform modifier is deforming my object. Following the logic of the first example, we could use, msdn.microsoft.com/en-us/library/bb342451(v=vs.110).aspx, How a top-ranked engineering school reimagined CS curriculum (Ep. 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. Which reverse polarity protection is better and why? Connect and share knowledge within a single location that is structured and easy to search. Using LINQ to change values in collection, How a top-ranked engineering school reimagined CS curriculum (Ep. Generic Doubly-Linked-Lists C implementation. rev2023.5.1.43405. Why refined oil is cheaper than cold press oil? A boy can regenerate, so demons eat him for years. Even if there is a solution out there, I'm not sure I'd use Linq for something like this. How can I control PNP and NPN transistors together from one pin? I think I'm not undertanding LINQ well. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How a top-ranked engineering school reimagined CS curriculum (Ep. Why did US v. Assange skip the court of appeal? 8 Answers. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? You can use Magiq, a batch operation framework for LINQ. I assume you want to change values inside a query so you could write a function for it Two MacBook Pro with same model number (A1286) but different year. Why is it shorter than a normal address? Note that you can add a ForEach extension method which performs an action on each object, but I would still recommend avoiding that. LINQ stands for Language Integrated Query. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. In general Linq is a query- not an update tool, but you can use a foreach: var currentRequests = Great answer. I need to store the rank because the price may change afterward. I have a bit of code that i'd like to turn into a linq expression (preferably with lambdas) to make it easier to use as a delegate. Making statements based on opinion; back them up with references or personal experience. LINQ is not really intended to be used for updating collections. 1. Asking for help, clarification, or responding to other answers. I found SingleOrDefault to be my answer of choice - same as Single but returns 'null' if it can't find it. 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 => and MatchingColumnName1 and MatchingColumnName2 are properties of collections. dont forget the return syntax it took me one hour, Very neat! I'm trying this but can't get it right: Which language's style guidelines should be used when writing code that is supposed to be called from another language? rev2023.5.1.43405. What does LINQ return when the results are empty, Use LINQ to get items in one List<>, that are not in another List<>. Most of these methods (First, Single, Any, ) cannot be. Asking for help, clarification, or responding to other answers. 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. This new list is then discarded. Very useful. The i.age = 10 part is not different from the item.age = 10 part. What's the cheapest way to buy out a sibling's share of our parents house if I have no cash and want to pay less than the appraised value? How would you do a "not in" query with LINQ? In my application I have a list of items I need to sort by price and set a rank/position index for each item. How do I remedy "The breakpoint will not currently be hit. Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). When do you use in the accusative case? Why did US v. Assange skip the court of appeal? Now, the only reason I added count was so that once 10000 items in a have been updated, the loop will stop, otherwise it will take a very long time to go thru all of the items. To use a linq statement to get a new List of CorrectionQuota you would do something like this: Transform the results into what you want first and then make the new List. However, those are all lamda expression style. is there such a thing as "right to be heard"? //using linq list = Students.Where (s => s.Name == "ABC").ToList (); //traditional way foreach (var student in Students) { if (student.Name == "ABC") list.Add (Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement). Making statements based on opinion; back them up with references or personal experience. It can be done this way as well foreach (Company company in listofCompany.Where(d => d.Id = 1)).ToList()) Short story about swapping bodies as a job; the person who hires the main character misuses his body. I really don't understand why you say it's not meant for this. Besides, the LINQ equivalent probably wouldn't be any less verbose than my example above. I just want something more concise that can be used more easily in a delegate without creating a multi-line monster. I want to compare these lists using LINQ and if IDs from both lists are equal, I want to set WorkingID in the first list, A list. This search will find the first or default value, which it will return. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? When do you use in the accusative case? How is this any different? You can't modify a collection while you're iterating it. Connect and share knowledge within a single location that is structured and easy to search. How to call asynchronous method from synchronous method in C#? Folder's list view has different sized fonts in different folders. It's not them. Find centralized, trusted content and collaborate around the technologies you use most. from c in listOfCompany where c.id == 1 select c => You could make it O(n + m) (assuming only a small number of items from a match each item in b) by using a hash table. { By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Certainly, foreach is the right way. What is the Efficiency and Performance of LINQ and Lambda Expression in .Net? What differentiates living as mere roommates from living in a marriage-like relationship? This should work Of course you can write your own ForEach extension for IEnumerable but I remember I had side-effect with it. var list = from something in someList select GetModifiedObject (x); // but change one property private MyType One possible way to do this is to use ToLookup(): Another way to do basically the same thing would be using join: Also, you should really use better variable names. If you want the index of the element, this will do it: You can't get rid of the lambda in the first pass. When to use .First and when to use .FirstOrDefault with LINQ? Web3. It's about querying, i.e. How do I clone a list so that it doesn't change unexpectedly after assignment? All values are updated in one line of code and you browse the List only ONE time. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? An interesting question, but Linq is about querying and what you're doing here doesn't look much like a query to me. "Signpost" puzzle from Tatham's collection. 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. Does a password policy with a restriction of repeated characters increase security? Without digging into what your actual conversion function is doing. Do I need to check if list is null first? Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? I think using Join then looping through the list would be more efficient. rev2023.5.1.43405. how to check for a value in a list of decimal C#, C# Select From Json List Using Where Clause, String search function XML file with ASP.NET MVC. For Starship, using B9 and later, how will separation work if the Hydrualic Power Units are no longer needed for the TVC System? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. { The list IS updated as expected. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? Passing negative parameters to a wolframscript. Connect and share knowledge within a single location that is structured and easy to search. Close enough for me, I think. Which method performs better: .Any() vs .Count() > 0? Thanks for contributing an answer to Stack Overflow! Asking for help, clarification, or responding to other answers. See below for arguments against it. Thanks for contributing an answer to Stack Overflow! foreach(var item in self) { Use LINQ to get items in one List<>, that are not in another List<>, Simple deform modifier is deforming my object. 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. Also, you How are engines numbered on Starship and Super Heavy? It only takes a minute to sign up. 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; }) Here is an example. Reme. If it is possible, how? The code looks like this: For the life of me, I can't seem to figure this one out. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? Note that this will throw if the item doesn't exist. Why is it shorter than a normal address? For multiple. 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 learn more, see our tips on writing great answers. x.Value = Convert.ToDouble(string.Format("{0:0.0}", x)) : x.Value = x.Value); This gives you an I don't really see how this is any different. 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. Why did US v. Assange skip the court of appeal? You can create a extension method: public static IEnumerable Do(this IEnumerable self, Action action) { 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. Does a password policy with a restriction of repeated characters increase security? 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. I have my doubts that my box is 18,000 times faster than yours, so something else must be at work here. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. 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? Find centralized, trusted content and collaborate around the technologies you use most. Not the answer you're looking for? Thanks for contributing an answer to Stack Overflow! Asking for help, clarification, or responding to other answers. Was Aristarchus the first to propose heliocentrism? 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. Identify blue/translucent jelly-like animal on beach. When to use .First and when to use .FirstOrDefault with LINQ? Not the answer you're looking for? I like this. Why don't we use the 7805 for car phone chargers? It should not be hard to analyze the complexity of this. Assigning a value to a parameter of an lambda does not change the queried collection Linq expression to set all values of an array to a given value, How a top-ranked engineering school reimagined CS curriculum (Ep. Asking for help, clarification, or responding to other answers. What is the difference between Python's list methods append and extend? What were the most popular text editors for MS-DOS in the 1980s? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Update all objects in a collection using LINQ, Concat all strings inside a List using LINQ, How to use LINQ to select object with minimum or maximum property value, Searching if value exists in a list of objects using Linq, All possible array initialization syntaxes, String.IsNullOrWhiteSpace in LINQ Expression. 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. I think your code is perfectly readable and won't improve much if you force it to have lots of lambdas and such. Concat all strings inside a List using LINQ, Using LINQ to remove elements from a List. Code Review Stack Exchange is a question and answer site for peer programmer code reviews. Not the answer you're looking for? Find centralized, trusted content and collaborate around the technologies you use most. Is there a generic term for these trajectories? Use LINQ to get items in one List<>, that are not in another List<>. What's the cheapest way to buy out a sibling's share of our parents house if I have no cash and want to pay less than the appraised value? Is there any known 80-bit collision attack? 20 : 30)) What is the symbol (which looks similar to an equals sign) called? WebYou can try LINQ. Is there any known 80-bit collision attack? Making statements based on opinion; back them up with references or personal experience. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Why did US v. Assange skip the court of appeal? Google "LINQ side effects" for more information. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Can my creature spell be countered if I cast a split second spell after it? When do you use in the accusative case? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Was Aristarchus the first to propose heliocentrism? 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" ? Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? You need change increment to postfix (rankPosition++) or initial value of rankPosition to 0. Would My Planets Blue Sun Kill Earth-Life? Let me try to look it up. Making statements based on opinion; back them up with references or personal experience. If you want to modify all returned objects, you still have to use a loop to iterate over the objects. Not the answer you're looking for? 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. So, if you wanted to grab only a specific property from a collection you would use that. Why don't we use the 7805 for car phone chargers? You really shouldn't use LINQ to perform side effects. 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. from c in listOfCompany where c.id == 1 select c => Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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. You can select multiple fields using linq Select as shown above in various examples this will return as an Anonymous Type. Weighted sum of two random variables ranked by first order stochastic dominance. 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. To learn more, see our tips on writing great answers. MathJax reference. Eric Lippert wrote a great blog post about the subject that is worth a read: "foreach" vs "ForEach". To learn more, see our tips on writing great answers. When to use .First and when to use .FirstOrDefault with LINQ? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. "Signpost" puzzle from Tatham's collection. Not the answer you're looking for? I'm querying to return every element of a List, so I can then set those values. What should I follow, if two altimeters show different altitudes? Can you perhaps include some description of your answer instead of just posting a blob of code? What were the most popular text editors for MS-DOS in the 1980s? Making statements based on opinion; back them up with references or personal experience. Besides checking for it's existance with if, first. Normally I use a for loop or anonymous delegate to do it like this: LINQ is new for me. Two points. Set list property value using LINQ ForEach. According to this link: Update all objects in a collection using LINQ, you can do this: repo.getAll().Select(c => {c.B = value; return c;}).ToList(); However, Hm, using your example and stuffing various random data into the objects into the two lists of the sizes you specify, it executes in less than 1/100 second on my machine. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Can anyone help me with a working expression? Should I re-do this cinched PEX connection? There are a few ways (note that this is not a complete list). Why? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. It's exactly what I was looking for, How a top-ranked engineering school reimagined CS curriculum (Ep. > 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. The code will look something like this. Connect and share knowledge within a single location that is structured and easy to search. At the moment I am doing it like this: You could do it using the let keyword. Would My Planets Blue Sun Kill Earth-Life? I've tried using ForEach and various forms of select, etc.. nothing seems to work right.

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