Connect and share knowledge within a single location that is structured and easy to search. rev2023.5.1.43405. dont forget the return syntax it took me one hour, Very neat! Identify blue/translucent jelly-like animal on beach. To learn more, see our tips on writing great answers. 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. 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 disagree, it is in fact a query, but a query with side effects. it will be discarded but, how will you replace older list values? Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Making statements based on opinion; back them up with references or personal experience. 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? Asking for help, clarification, or responding to other answers. I've tried using ForEach and various forms of select, etc.. nothing seems to work right. Learn more about Stack Overflow the company, and our products. Even by limiting it like this, it still takes around 3 min. Do I need to check if list is null first? 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. It's not LINQ, and it's not really much different to your nested for loops, just slightly less verbose. How do they work? Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? What should I follow, if two altimeters show different altitudes? 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. 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. The best answers are voted up and rise to the top, Not the answer you're looking for? Asking for help, clarification, or responding to other answers. One other point I should mention is that the Select method does a projection of some specific information to return to an IEnumerable. (from c in listOfCompany where c.id == 1 select c).First ().Name = "Whatever Name"; For Multiple updates. c# - Set values with a Linq-Query? - Stack Overflow What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? If you need to add any IEnumerable collection of elements to the list you need to use AddRange. 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. He also rips off an arm to use as a sword. Making statements based on opinion; back them up with references or personal experience. 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? using Linq would be: listOfCompany.Where(c=> c.id == 1).FirstOrDefault().Name = "Whatever Name"; How would you do a "not in" query with LINQ? For multiple. Remember that linq is a querying language, which means all you can do is query it. The i.age = 10 part is not different from the item.age = 10 part. I need to store the rank because the price may change afterward. Is there any known 80-bit collision attack? You are essentially doing a join and then an update. MathJax reference. 8 Answers. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I think you try to add a complete list instead of a single CheckItems instance. To learn more, see our tips on writing great answers. I really don't understand why you say it's not meant for this. Not the answer you're looking for? 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. Use LINQ to get items in one List<>, that are not in another List<>, Simple deform modifier is deforming my object. 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. UPDATE This can be simplified to be listOf 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 "Signpost" puzzle from Tatham's collection, Simple deform modifier is deforming my object. List1 and List2 are two collections. When to use .First and when to use .FirstOrDefault with LINQ? 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. Connect and share knowledge within a single location that is structured and easy to search. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? This assumes that there are only 3 types of name. What is Wario dropping at the end of Super Mario Land 2 and why? 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. How are engines numbered on Starship and Super Heavy? Here I have a simple example to find an item in a list of strings. Web3. One more way to check the existence of an element in a List: You want to search an object in object list. In both cases , the update is not done with Linq :). c# - How to update value in a List using LINQ - Stack Overflow How to call asynchronous method from synchronous method in C#? Find centralized, trusted content and collaborate around the technologies you use most. I have my doubts that my box is 18,000 times faster than yours, so something else must be at work here. rev2023.5.1.43405. It's about querying, i.e. Ubuntu won't accept my choice of password. Does a password policy with a restriction of repeated characters increase security? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Here is one way to rewrite your method to use LINQ: You can use FirstOfDefault with the Where LINQ extension to get a MessageAction class from the IEnumerable. I don't have a C# compiler here but maybe AddRange instead of Add works: 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. It's exactly what I was looking for, How a top-ranked engineering school reimagined CS curriculum (Ep. Not the answer you're looking for? For multiple. The list may be a class with several properties and some are used for search. 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. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? Without digging into what your actual conversion function is doing. c# - Add items to list from linq var - Stack Overflow What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? When do you use in the accusative case? foreach(var item in self) { How a top-ranked engineering school reimagined CS curriculum (Ep. I have another List that contains the data, this just maps each element of the string array to a time when they last changed. I have a list where i whant to change the value of a double property in that list if that property has decimals. I think using Join then looping through the list would be more efficient. 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. If we had a video livestream of a clock being sent to Mars, what would we see? Which reverse polarity protection is better and why? WebYou can try LINQ. That's all it does. Not the answer you're looking for? This article shows the three ways in which you can write a LINQ query in C#: Use query syntax. Use method syntax. Use a combination of query syntax and method syntax. The following examples demonstrate some simple LINQ queries by using each approach listed previously. Does a password policy with a restriction of repeated characters increase security? Not knowing the full extent of the data types behind the MatchA, MatchB and ToUpdate properties, it'll be difficult to give an answer which completely solves your performance issues. You can create a extension method: public static IEnumerable Do(this IEnumerable self, Action action) { I didn't know either Single() or SingleOrDefault(). What is the symbol (which looks similar to an equals sign) called? Thanks for contributing an answer to Stack Overflow! I mean, if PopulateChanges() is returning you a List<> of DateTime arrays, and you are going through all of them and setting them to DateTime.MinValue, what exactly is the code unit that you want to put in the delegate? How can I control PNP and NPN transistors together from one pin? 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. LINQ is not really intended to be used for updating collections. Thanks for contributing an answer to Stack Overflow! If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? 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. c# - ToList method in Linq - Stack Overflow Connect and share knowledge within a single location that is structured and easy to search. Asking for help, clarification, or responding to other answers. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. See below for arguments against it. Find centralized, trusted content and collaborate around the technologies you use most. //d 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. How do I make a flat list out of a list of lists? What is the symbol (which looks similar to an equals sign) called? Folder's list view has different sized fonts in different folders. How to set a value in one list when comparing it with other list Where does the version of Hamapil that is different from the Gemara come from? rev2023.5.1.43405. Which language's style guidelines should be used when writing code that is supposed to be called from another language? Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Normally I use a for loop or anonymous delegate to do it like this: LINQ is new for me. I suspect that this can be written shorter using LINQ over objects syntax. When do you use in the accusative case? 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, 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? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Is a downhill scooter lighter than a downhill MTB with same performance? 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, There is no ForEach for IEnumerable. Making statements based on opinion; back them up with references or personal experience. 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: //d How is this any different? correctionQoutas is a custom object that has four properties. 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. and do I need to check if _list is null in the form of from .. in _list? With LINQ2SQL you query the database and then modify the returned objects. Which reverse polarity protection is better 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. Use LINQ to get items in one List<>, that are not in another List<>. The check if you have decimal places is unneccessary too, since the output will be a double anyway. I use a simple list here. A boy can regenerate, so demons eat him for years. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Thanks. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This will give syntax error, How to set a value in one list when comparing it with other list using LINQ, How a top-ranked engineering school reimagined CS curriculum (Ep. Is a downhill scooter lighter than a downhill MTB with same performance? "Signpost" puzzle from Tatham's collection. At the moment I am doing it like this: You could do it using the let keyword. How do I clone a list so that it doesn't change unexpectedly after assignment? Connect and share knowledge within a single location that is structured and easy to search. It can be done this way as well foreach (Company company in listofCompany.Where(d => d.Id = 1)).ToList()) Asking for help, clarification, or responding to other answers. Asking for help, clarification, or responding to other answers. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I just want to get a taste of LINQ searching from enumeration case. LINQ is about querying, not for updating collections. I would externalize that part into a function to make it more manageable. 10 : (tl.name == "marks" ? To learn more, see our tips on writing great answers. Why did US v. Assange skip the court of appeal? 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The below is practically the same as the answer provided by Florian Schmidinger: is there such a thing as "right to be heard"? The ToList is making a list, populating it, and the immediately discarding it. This search will find the first or default value, which it will return. Parabolic, suborbital and ballistic trajectories all follow elliptic paths. Enumerable.Empty()) instead of list. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? An interesting question, but Linq is about querying and what you're doing here doesn't look much like a query to me. What differentiates living as mere roommates from living in a marriage-like relationship? Set list property value using LINQ ForEach. 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. create enumerables over existing collections. How are engines numbered on Starship and Super Heavy? rev2023.5.1.43405. Find centralized, trusted content and collaborate around the technologies you use most. It only takes a minute to sign up. 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. In my application I have a list of items I need to sort by price and set a rank/position index for each item. A new List, yes - but containing the same items, which will be updated correctly. And the enumerable containing the objects isn't modified at all. Why does Acts not mention the deaths of Peter and Paul? In general Linq is a query- not an update tool, but you can use a foreach: var currentRequests = Are there any canonical examples of the Prime Directive being broken that aren't shown on screen? What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? I want to do: Just change all values for a property in all elements of my collection. 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. Asking for help, clarification, or responding to other answers. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, That's great. Canadian of Polish descent travel to Poland with Canadian passport. Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? Can anyone help me with a working expression? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. IEnumerable vs List - What to Use? Connect and share knowledge within a single location that is structured and easy to search. Google "LINQ side effects" for more information. Two points. Extracting arguments from a list of function calls. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? It's not them. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Was Aristarchus the first to propose heliocentrism? I think your code is perfectly readable and won't improve much if you force it to have lots of lambdas and such. Think about a typical Linq2SQL query where you query data and then update the values. 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. Thanks for contributing an answer to Stack Overflow! Was Aristarchus the first to propose heliocentrism? If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? Double StartTime, Double EndTime, Double Value and string Id. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. What is Wario dropping at the end of Super Mario Land 2 and why? Two MacBook Pro with same model number (A1286) but different year. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Most of these methods (First, Single, Any, ) cannot be. EDIT: If you want to modify all returned objects, you still have to use a loop to iterate over the objects. While you can use a ForEach extension method, if you want to use just the framework you can do collection.Select (c => {c.PropertyToSet = value; return Can I use LINQ to find an item in the list? Making statements based on opinion; back them up with references or personal experience. The following example depicts the behavior of the Enumerable.Distinctmethod on a You can remove the .ToList call. No symbols have been loaded for this document." Find centralized, trusted content and collaborate around the technologies you use most. Where can I find a clear diagram of the SPECK algorithm? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. Why refined oil is cheaper than cold press oil? Can my creature spell be countered if I cast a split second spell after it? ex. rev2023.5.1.43405. Why did US v. Assange skip the court of appeal? 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 Why are players required to record the moves in World Championship Classical games? Use method syntax. FYI, I know that DateTime defaults to MinValue, in reality this is clearing the arrays to default after they've already been set. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? First, there's no real need to use. (from c in listOfCompany where c.id == 1 select c).First ().Name = "Whatever Name"; For Multiple updates. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? What is the best way to give a C# auto-property an initial value? Weighted sum of two random variables ranked by first order stochastic dominance. 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. Not the answer you're looking for? Short story about swapping bodies as a job; the person who hires the main character misuses his body. Why don't we use the 7805 for car phone chargers? Asking for help, clarification, or responding to other answers. (Your question does not sound like you want to copy the original objects). Why did US v. Assange skip the court of appeal? You're trading one assignment for one condition, that shouldn't change much. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Ok, this should hopefully be of some help: I would also look into PLINQ as you have a lot of data to plow through. Why waste the time on it. Connect and share knowledge within a single location that is structured and easy to search. If you really want to use linq, you can do something like this. Use MathJax to format equations. 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.
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