Code Review Stack Exchange is a question and answer site for peer programmer code reviews. :p. I didn't ask u for difference var and IEnumerable. Not the answer you're looking for? using System.Collections.Generic; By using this website, you agree with our Cookies Policy. Display(new List
{ true, false, true }); The following code example shows us how we can convert a List data structure to an IEnumerable data structure with the AsEnumerable() function of LINQ in C#. The graphdata class is public, but its members are private by default. Use AsEnumerable to return the argument typed as a generic IEnumerable. Agree View this solution by signing up for a free trial. Re knowing what it is - hover ;) or better: use a profiler (such as mvc-mini-profiler) so that you can keep a close eye on the queries it is running at all times. You can not convert rows in the Customers table to IEnumerable<DataRow>. How to Convert Horizontal List to Vertical List in Excel? Find centralized, trusted content and collaborate around the technologies you use most. Examples. IEnumerable is an interface defining a single method GetEnumerator() that returns an IEnumerator interface. using System.Collections; I think Louis has won the goldfish. Of course, restrictions apply to when you can use 'var'. Convert the List to IEnumerable With the Typecasting Method in, Convert the List to IEnumerable With the LINQ Method in, Get the First Object From List Using LINQ. Can the supreme court decision to abolish affirmative action be reversed at any time? List class represents the list of objects which can be accessed by index. Seem to me very much like knife in monkey's hand. This forum has migrated to Microsoft Q&A. variance to do that, otherwise you can iterate on the list, cast one element to another and use
@Mr. I am reading this article to understand difference between var and IEnumerable. I should say that there is no common ancestry (except object) between the two enumerated classes. Find centralized, trusted content and collaborate around the technologies you use most. How would you do a "not in" query with LINQ? If you used var or IQueryable, you would retrieve only the first row. IEn1 & Ien2 both contain an Id field (in reality an index), in1.Property = IEn2.Where(a=>in1.ID == a.ID).Select(a=>a.property2). Possible Duplicate: How can I convert var matlab code into Python code, Conversion failed while converting var char value active to int. And a List and you want to convert it to an Class2[], you can do this: It should be simple enough to understand. Is this something you were looking for? List class also provides the methods to search, sort, and manipulate lists. 585), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned. As for whether it's IEnumerable or IQueryable - that depends on the type of dataBase.CaseTables. This forum has migrated to Microsoft Q&A. Grappling and disarming - when and why (or why not)? { second, selecting the matching item and updating that way. Never experienced it though irl (and obviously that is why I mentioned "No") and even more - it looks like a big surprise for me, Actually, in the example I imagine var would use IQueryable-of-T. @Marc could you tell me how you come out with this idea? What is the earliest sci-fi work to reference the Titanic? You do this by invoking the AsEnumerable operator. A Chemical Formula for a fictional Room Temperature Superconductor. This is wrong, the resultant type will always be the type returned, whether specified explicitly or not; you would need to know the type anyway, if you intend to use the result! Convert list of string to list of list in Python. Program to convert linked list by alternating nodes from front and back in Python. Use IEnumerable when you already know the type of query result. We can also use the typecasting method to store an object of the List data type into an object of the IEnumerable data type, as shown in the following code example. Is Logistic Regression a classification or prediction model? IEnumerable is good for in-memory collection. Novel about a man who moves between timelines. Of course, it works because it requires to I set a generic type. Although the difference is going to be negligible most of the time. Grappling and disarming - when and why (or why not)? Further, there are some cases where knowing that an enumerator will behave as a value type could be semantically useful (e.g. using System.Collections.Generic; var list = GroupViewModel.Convert<GroupViewModel>(model); There is GroupViewModel extends from BaseViewModel. { static void Main() You just let the compiler determine the type. class Program Emanuel Varga, @Mike - I had never heard of the Tuple class, but I', only using 3.4, @Emanuel - I don't think that's what I am after. Like all good ideas its obvious when someone else shows you. Other than heat, Beep command with letters for notes (IBM AT + DOS circa 1984). @Daniel IEnumerable uses LINQ-to-Objects. Use IEnumerable when you already know the type of query result. I hadn't considered Extensions as a solution @Louis. It's also very nice when you want to discover the not-so-obvious type of a variable (via IntelliSense) - "LINQ" rings some bells. But the where clause references a user-defined client-side method (isValidProduct), which cannot be converted to SQL. make me clear about 3 and 4 if u know. class Program ;=), http://msdn.microsoft.com/en-us/library/bb386921.aspx. 20 Bay Street, 11th Floor Toronto, Ontario, Canada M5J 2N8
I think I'm still confused about the IQueryable and IEnumerable. By contrast, if one calls such a method multiple times with a value type like List.Enumerator, each call will copy the enumeration state to a new heap object which implements IEnumerator, pass that object to the method (which will read five items through it), and then abandon that object and its associated space (leaving the enumeration state associated with the original variable unaffected). why does music become less harmonic if we transpose it down to the extreme low end of the piano? Just trying to grab the table from my LINQ DataConext and use it as a DataGrid DataSource. Ask your own question & get feedback from real experts. Making statements based on opinion; back them up with references or personal experience. Idiom for someone acting extremely out of character, Is there and science or consensus or theory about whether a black or a white visor is better for cycling? But how can I reduce this generic casting to it will get GroupViewModel type automaticaly when I call it so: var list = GroupViewModel.Convert(model);. Everything is wrong here, so briefly at least: A note on usage of var, though, to give a broader set of notions: using var is generally only a good idea when the resultant type is evident based on the current statement - I don't really understand Darren's reasoning or how that would ever be useful, but consider the following: var is a contextual keyword that implicitly types a variable. It only takes a minute to sign up. All Rights Reserved. This difference could be important if e.g. Experts Exchange is like having an extremely knowledgeable team sitting and waiting for your call. static void Main() IEnumerable and IQueryable, which one does it use when I use the var keyword? "var" is usefull to make your code less bloated when the type of the variable is evident from its declaration. Returning IEnumerable vs. IQueryable. Use Var type when you want to make a "custom" type on the fly. Just I learn C# only. class Program what is the difference in List and IEnumerable, difference between IEnumerable vs Dictionary C#. If one calls such a method multiple times with a variable of type IEnumerator, each call will read the next five items from the enumeration. why does music become less harmonic if we transpose it down to the extreme low end of the piano? I prompt an AI into generating something; who created it: me, the AI, or the AI's author? Here i think you can create your own class and use it like List instead of List. While I can see your logic, I wanted a piece of code that a relatively inexperienced user could look at without scratching his left earlobe. LINQ provides a very elegant and powerful way to work with sequences of data in C#. Did the ISS modules have Flight Termination Systems when they launched? Is it possible? Question regarding IEnumerable and IEnumerator, Var vs IEnumerable when it comes to Entity Framework. Why would a god stop using an avatar's body? List class can be used to create a collection of different types like integers, strings etc. Suggest you find a better article. https://msdn.microsoft.com/en-us/library/bb384054.aspx. C# Enjoy unlimited access on 5500+ Hand Picked Quality Video Courses. But one thing that can be a bit tricky is when you need to introduce . Is there any particular reason to only include 3 out of the 6 trigonometry functions? Disappointment: I was too lazy to find one, but here it is: @zerkms it really can - see the example I added, @Marc Gravell: yep, already did and +1'd you. That also seems clumsy. ", Converting models into a list of ViewModels [closed], How to get the best value out of Code Review - Asking Questions, How Bloombergs engineers built a culture of knowledge sharing, Making computer science more humane at Carnegie Mellon (ep. const int _max = 1000000; Dot Net Perls is a collection of tested code examples. "Although, I can't understand why C# can't get generic type in this expression. Australia to west & east coast US: which order is better? How do I convert a LINQ query to a ienumerable LIST. How should I ask my new chair not to hire someone? If it was already IEnumerable then it will make no difference. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Mainly because I need to understand when I return. Do I owe my company "fair warning" about issues that won't be solved, before giving notice? if one wanted to be able to repeatedly re-enumerate part of a collection). Note that in probably 99% of cases, either value semantics or reference semantics would be equally acceptable in an enumerator; in the majority of those, value semantics would make code run faster, and only very rarely would it make code run meaningfully slower. For what purpose would a language allow zero-size structs? Casting a value type to reference type changes representation - the value needs to be boxed and the reference to the boxed value is returned. { Understand that English isn't everyone's first language so be lenient of bad
I am trying to pass the result of a LINQ query to a new WinForm in order to create a graph with the data, but cannot get the following code to work. This works for read-only access to a collection that implements that IEnumerable can be used with a foreach statement. 585), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Dealing with Entity Framework's lack of enum support, Caliburn Micro communication between list and edit viewmodels, Field wrappers for tracking and applying changes to database fields, Recursive search on Node Tree with Linq and Queue, Short story about a man sacrificing himself to fix a solar sail. Not a problem, glad I was able to help. Connect and share knowledge within a single location that is structured and easy to search. It isn't that I wanted =) But I like this solution! It will make a difference if the return type isn't the same, and this then changes composition. C# 'var' vs specific type performance, In term of performance does it make any difference to use var or IEnumerable in linq? Do you need your, CodeProject,
Although, I can't understand why C# can't get generic type in this expression. How to inform a co-worker about a lacking technical skill without sounding condescending. 3 & 4 is not clear to me. IEnumerable is an interface defining a single method GetEnumerator () that returns an IEnumerator interface. IEnumerable is good for in-memory collection. The variable declared by that is still statically typed, and the compiler will infer its type. What this all means: yes, using var can make a difference: it can make your code faster, in some cases much faster. {method} or Queryable. { I was under the assumption that Users is a DataTable (from a DataSet). msdn.microsoft.com/en-us/library/bb383973.aspx, How Bloombergs engineers built a culture of knowledge sharing, Making computer science more humane at Carnegie Mellon (ep. Cannot set Graph Editor Evaluation Time keyframe handle type to Free. Author wrote four points like following. In this example, LINQ to SQL (using the default generic Query) would try to convert the query to SQL and execute it on the server. Ugly, confusing, difficult to decipher andpossibly slow; all aspects I try to avoid in my code. More info about Internet Explorer and Microsoft Edge. Example example = new Example(); using System; Was the phrase "The world is yours" used as an actual Pan American advertisement? Assuming I have two IEnumerables that are a different cup of , and of the same Length, how do I write the same with IEnumerable and IEnumable? Sorry, but your solution doesn't work! It is the base interface for all non-generic collections that can be enumerated. First I have to get it working. How to transfer values from IEnumerable to IEnumerable, How To: Joining multiple DataTable using LINQ to DataSet. What are the pitfalls of using an existing IR/compiler infrastructure like LLVM? Why does var List(); work and var IEnumerable(); not work? Can we convert a List to Set and back in Java? .NET Framework Data and modeling ADO.NET SQL Server and ADO.NET C# Convert a Type to a Generic IEnumerable Article 09/15/2021 10 contributors Feedback In this article Example See also Use AsEnumerable to return the argument typed as a generic IEnumerable. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. After all that's what your original array code assumes too. Is there any advantage to a longer term CD that has a lower interest rate than a shorter term CD? Why not just use a standard ADO.NET SqlDataAdapter to fill a DataSet? It is also super handy when working with anonymous types, eg. See the following example. We can use the AsEnumerable () function of LINQ to convert a list to an IEnumerable in C#. using System.Linq; He has over 4 years of experience with Python programming language. class Example In term of performance does it make any difference to use var or IEnumerable in linq? Is IEnumerable different in VB.net and C#? } The keyword "var" is just syntactic sugar in C#. select cust; Which returns a collection of Customers rows. Why is there inconsistency about integral numbers of protons in NMR in the Clayden: Organic Chemistry 2nd ed.? After the question has been edited to contain working code, we will consider reopening it. {, using System; static void Main() "Users" is a table in my SQL Database that I'm pulling with LINQ ( simple query: from user in users select user). Behind the scenes the CLR will infer the variables type (When using var) at runtime, most likely to IEnumerable. Doesn't it follow the rules of stackoverflow?? using System.Diagnostics; LINQ equivalent of foreach for IEnumerable, Update crontab rules without overwriting or duplicating, Protein databank file chain, segment and residue number modifier. how can I differentiate between them? Here This example shows the yield contextual keyword in a method that returns IEnumerable<T>. The LINQ integrates the SQL query functionality with the data structures in C#. but what do I put in the place of using your suggestion? rev2023.6.29.43520. Just I learn C# only. Return The return value is a generic IEnumerable collection of ints. The following code example shows us how we can convert a List data structure to an IEnumerable data structure with the AsEnumerable () function of LINQ in C#. If a question is poorly phrased then either ask for clarification, ignore it, or. { Iterating using that is going to be faster than iterating through IEnumerator. Covered by US Patent, All of life is about relationships, and EE has made a viirtual community a real community. When you implement IEnumerable<T>, you must also implement IEnumerator<T> or, for C# only, you can use the yield keyword. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. "Error" does not tell anyone anything other than you got an error. Alternatively your code doesn't yieldresult beingIEnumerable so I cannot run the following: in order to pass the list in format, Public class TheClass(List list). Here is an indexing solution (which assumes no entries are ever deleted from the lists, which is true on my real-life case), "@Mike - I had never heard of the Tuple class, but I', only using 3.4". Any help will be greatly appreciated. This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL). It lifts everyone's boat. In order to use the composing interface, the stronger IQueryable interface must be used. This page was last updated on Mar 21, 2023 (edit). Don't tell someone to read the manual. var result =from row in SalesDT.AsEnumerable () where (row.Field<int> ("Item") == item) && (row.Field<int> ("Site") == site) select new { Date=row.Field<DateTime> ("Date"), Sales=row.Field<int> ("Sales"), SOH=row.Field<int> ("SOH") }; //IEnumerable<graphdata> result2 = result.OfType<graphdata> (); //var count = result.Count (); //resu. Chances are they have and don't get it. Beep command with letters for notes (IBM AT + DOS circa 1984). Is it possible? In the above code, we converted the List of integers ilist to the IEnumerable of integers enumerable with the as keyword in C#. static void Main() @AtishDipongkor it's: could you give me some useful links PLEASE. Do native English speakers regard bawl as an easy word? But how can I reduce this generic casting to it will get GroupViewModel type automaticaly when I call it so: var list = GroupViewModel.Convert(model);. what about IEnumerable or IQueryable? Pages are continually updated to stay current, with code correctness a top priority. Why do CRT TVs need a HSYNC pulse in signal? Questions containing broken code or asking for advice about code not yet written are off-topic, as the code is not ready for review. Learn more, C# Program to cast a type to its IEnumerable equivalent, Difference between IEnumerator and IEnumerable Interface in C#. The solution is to specify the client-side generic IEnumerable implementation of where to replace the generic IQueryable. How can one know the correct direction on a cloudy day? This can make difference even without IQueryable. using System.Collections.Generic; using System.Linq; using System; How Do I Convert A Var Type Data Into List Below Code Is No Working. This works for read-only access to a collection that implements that IEnumerable can be used with a foreach statement. {method} is used. Find out why thousands trust the EE community with their toughest problems. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. class Program Provide an answer or move on to the next question. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States. We can abstract the loop itself out. I gather that the LINQ result needs to be in IEnumerable format. class Example : using System; But if you wanted to fill a DataTable object with this . For what purpose would a language allow zero-size structs? for ex: in code below. You can convert it to list using .ToList () method. I am asking for those alternative ways. Novel about a man who moves between timelines. If you declared as var, the type of test is still IEnumerable in your example. If you absolutely, positively, have to pass DataTables to the UI for binding, then why use LINQ-to-SQL in the first place? Connect and share knowledge within a single location that is structured and easy to search. In the above code, we converted the List of integers ilist to the IEnumerable of integers enumerable with the ilist.AsEnumerable() function in C#. What is the status for EIGHT piece endgame tablebases? Var is also good for remote collection. static void Display(, using System; How to convert list into dictionary. It comes under the System.Collection.Generic namespace. We can convert the List data structure to the IEnumerable data structure with the as keyword in C#. For example: If this is actually a DB provider, the second should issue a "select COUNT(1) from Users" (1 row, 1 column) - however, the first will issue a "select * from Users" - n columns times m rows. All rights reserved. { using System.Linq; class Program 585), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Returning IEnumerable vs. IQueryable. static int[,] _grid = new int[15, 15]; +1 (416) 849-8900.
Can one be Catholic while believing in the past Catholic Church, but not the present? That will be the fastest way, and is vaguely understandable, and flexible due to the use of a delegate. Out of the thousands of errors that it could be should we guess? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. using System; What does the interface IEnumerable do in C#? I'm not sure I understand, but I think the differences between, stackoverflow.com/questions/41479/use-of-var-keyword-in-c, How Bloombergs engineers built a culture of knowledge sharing, Making computer science more humane at Carnegie Mellon (ep. Info We use IEnumerable and the foreach-loop to access, in sequence, all items in a 2D array. We make use of First and third party cookies to improve our user experience. The best answers are voted up and rise to the top, Not the answer you're looking for? Maisam is a highly skilled and motivated Data Scientist. This assumesthatboth IEnumerable contain the same number of elements and the order is the same. Example There is GroupViewModel extends from BaseViewModel. Couldn't do my job half as well as I do without it! On the other hand, it's probably a good idea for code which uses implementations of IEnumerator to be aware of what kind of implementation they may be using. Is it possible to "get" quaternions without specifically postulating them? Async Enumerable in C# (Part 1) .NET. var q = ( from t1 in Bank.Users join t2 in Bank.Questions on t1.Id equals t2.Id_Users select new UserInfo { Id = t1.Id, Name = t1.Name }); Now, q is an IEnumerable<UserInfo>. var is already a List! Affordable solution to train a team and make them project ready. {. What's the meaning (qualifications) of "machine" in GPL's "machine-readable source code"? using System.Collections.Generic; It doesn't really make a difference which one you use, more of a coding style IMO, I personally use var when returning something from a collection using LINQ rather than IEnumerable or IQueryable. Convert List to dictionary without using Linq and Var? 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? If I understand your question correctly I think. I don't want to 'transfer' anything to the IEnumerable, just update the contents of one with another, which is a perfectly legitimate thing to do. This tutorial will discuss the methods to convert a list to IEnumerable in C#. Please help to understand these point with examples. How could a language make the loop-and-a-half less error-prone? } Author wrote four points like following, point no. rev2023.6.29.43520. even in msdn.microsoft.com most of the examples use var. You can combine the LINQ "operators" (such as Select or Where) to form "pipelines" that filter and transform elements of IEnumerable<T> sequences. When you use IEnumerable you are explicitly stating the type to be defined, were as var will use type inference. email is in use. I don't believe that IEnumerable is any more beneficial for in memory collections at all. What error do you have? No. This
To learn more, see our tips on writing great answers. I believe the third item is silently comparing against, @MarcGravell I was just adding a parenthesised caveat for that last one - I knew the danger. If the type ofMyListhad beenIEnumerable, the return type ofMyList.GetEnumerator()would have beenIEnumerator`, which has reference semantics. { 1. He loves solving complex problems and sharing his results on the internet. What do you do with graduate students who don't want to work, sit around talk all day, and are negative such that others don't want to be there? What is the difference between IEnumerable and arrays? using System.Collections.Generic; Want to Convert my data in Var format to List type. IEnumerable vs List - What to Use? How to convert list to dictionary in Python? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Copyright TUTORIALS POINT (INDIA) PRIVATE LIMITED. Visit Microsoft Q&A to post new questions. What is the status for EIGHT piece endgame tablebases? Thank you very much! We can use the AsEnumerable() function of LINQ to convert a list to an IEnumerable in C#. DataClasses1DataContext Northwind = new DataClasses1DataContext (); IEnumerable<Customers> query = from cust in Northwind.Customers. In your code above (assuming dataBase.CaseTables is IQueryable backed by LINQ to SQL or some similar provider), if you wrote test.First(), you could retrieve lots of rows from the database to get only the first one. IEn1.Update(IEn2,(a,b)=>a.property1 = b.property2); How about this one, using these (very) contrived example classes: Here's the call to the UpdateWith method: I would add some checks against same length etc, but you get the drift. With regards to point 3 and 4. 4 Answers Sorted by: 7 The IEnumerable<T> interface is covariant, but covariance doesn't work with value types. What should be included in error messages? Visit Microsoft Q&A to post new questions. Best Regards,
yield to return it (given that they are variance of one another). { Difference between var and IEnumerable in C#? It seems that you are looking for something like this: If you're using .Net 4.0 you can use
Why exactly do you need this, maybe someone can suggest an alternative way of doing it? 1996-2023 Experts Exchange, LLC. Let's make it more readable than just keeping it in objects. how can we know which one is IEnumerable and which one is IQueryable? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. As we all want to make our code more efficient or improve it in one way or another. I am reading this article to understand difference between var and IEnumerable. Is Logistic Regression a classification or prediction model? {. IEnumerable is basically a read only interface, you cannot "transfer" anything to an IEnumerable. By the way, VAR in this case becomes the "Class" , not the IEnumerable so it's not going to work. It is the base interface for all non-generic collections that can be enumerated. Use Var type when you want to make a "custom" type on the fly. this third item is pure poppycock; it makes no sense in and of itself; Asking for help, clarification, or responding to other answers. var is just an implicitly typed local variable. You can fix that error by declaring the members as public too: Thanks for your help, but how do I pass this to the new FORM? var is only syntax for the programmer - it doesn't change the semantics at all. If a polymorphed player gets mummy rot, does it persist when they leave their polymorphed form? How can one know the correct direction on a cloudy day? what about IEnumerable or IQueryable? It will drag the data over the network, materialise it into objects, and then (LINQ-to-Objects) count the objects. How should I ask my new chair not to hire someone? (And in an easy-to-understand way for the casual bug fixer / maintenance programmer).
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