The IEnumerable that contains the elements to be cast to type TResult. In this Model, I have an attribute called: public List DependentsDocuments {get; set; }: I'm trying to bring benefits that contain the depedentID equal of the parameter. Asking for help, clarification, or responding to other answers. But I would say that having a lazily evaluated structure coming straight from the DB layer and leaving the DB layer is likely to be a, "harsh" was a poor choice of words on my part. Further discussion is available via this reference. Awesome! Maybe you could be a little more specific : where are you getting this error? Assume only IEnumerable functionality is required by the caller and my question can be reworded into: How do I signify to the caller that each enumeration may be expensive? The compiler is told that GetHistory returns IEnumerable, and even though it is a list, it doesn't know that. Return a List. In fact, IObservable implements IEnumerable. Convert System.Collection.Generic.IEnumerable<System.Text - Ocelot20. An explicit conversion exists (are you missing a cast?)". Question about ActionResult<IEnumerable<Something>> #3224 - GitHub You get that error because myClass.GetHistory(); returns IEnumerable, which is not same as List at compile time, although it is actually List at runtime. My mongodb has a colletion called Employee. Applies to The values returned by the IEnumerable interface are read-only. c# - Cannot convert type IEnumerable to List - Stack Overflow Compiler Error CS0266 | Microsoft Learn Program to convert linked list by alternating nodes from front and back in Python. Convert list of string to list of list in Python. An IEnumerable<int> represents multiple int values - which one do you want to assign to the variable "a"? To learn more, see our tips on writing great answers. I didn't downvote it, but I'd guess the reason is the redundant creation of a new list instead of the reuse of the existing one. Also your UserLogin method is void so you can't return anything (you are trying "return user", you can only just "return"). Can I mark the async method (GetProductTypes ()) as Task<actionresult<ienumerable>> too? Is there any political terminology for the leaders who behave like the agents of a bigger power? Provide an answer or move on to the next question. The number of times the method is called, as well as whether or not the consumer iterates over the result would be the determining factor. It only takes a minute to sign up. If they enumerate the whole lot several times, then a ToList() makes sense to them to perform. What is the difference between IEnumerable and IQueryable in C#? Why did Kirk decide to maroon Khan and his people instead of turning them over to Starfleet? List elements can be accessed or manipulated as follows: The namespace must be imported to use the ToList function as follows: Below is the syntax of the ToList() method. Adverb for when a person has never questioned something they believe, Formulating P vs NP without Turing machines. @Ocelot20 OK, I think my Update 1 clarifies what I'm trying to achieve. Thanks for your answer, but I'm a bit confused, you're asking what the code that calls it does then saying I shouldn't care about what the caller does. CS8625 - Cannot convert null literal to non-nullable reference type. A List in C# already implements an IEnumerable but you may still feel the need to convert a List to IEnumerable in C#. If they don't enumerate the whole lot, then a ToList() would be a waste for me (or the caller) to perform. Making statements based on opinion; back them up with references or personal experience. 20 Bay Street, 11th Floor Toronto, Ontario, Canada M5J 2N8 Abdullahi is a full-stack developer and technical writer with over 5 years of experience designing and implementing enterprise applications. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Like I mentioned before, there are plenty of acceptable reasons to return a lazily evaluated. Should i refrigerate or freeze unopened canned food items? ), An explicit conversion exists (are you missing a cast? Use the select clause of a query to perform other conversion types, like the implicit numeric conversions. This is essentially what this comes down to. Solution 1 The error message are pretty explicit: 'MyProjectJTable.Models.Student' does not contain a constructor that takes 0 parameters Which means you can't do this: C# a => new Student () You need to look at your Student class and find out which constructors are available, and call one of those with the appropriate parameters. Does the DM need to declare a Natural 20? Is it possible to notify a user of a new message in my Flutter chat app without Firestore or FCM? If an element cannot be converted to type TResult, this method throws a InvalidCastException. Learn more, C# Program to cast a type to its IEnumerable equivalent, Difference between IEnumerator and IEnumerable Interface in C#. In some applications this solution might not be viable due to the performance impact, and you might feel uneasy about the loss of control here (this is where IoC comes in handy). How do i convert IEnumerable<int> to int You need to call ToList at the end of your Select in order to get back a list, instead of an IEnumerable. Method returning IEnumerable<T> should ToList() or not ), Error: "Cannot implicitly convert type 'long' to 'int'. Cannot implicitly convert type 'System.Collections.Generic.IEnumerable An explicit conversion exists (are you missing a cast?). 234k 27 338 445 asked Jun 26, 2012 at 12:06 CC Inc 5,812 3 33 64 Hi! Connect and share knowledge within a single location that is structured and easy to search. The program below shows how we can use ToList() method to convert an IEnumerable to a list. Like every other interface, it exposes a method. Converting models into a list of ViewModels [closed] The ToList<TSource>(IEnumerable<TSource>) method forces immediate query evaluation and returns a List<T> that contains the query results. You can append this method to your query in order to obtain a cached copy of the query results. Use an "Assign" activity to convert the IEnumerable<> to a List using the . CS8631 - The type cannot be used as type parameter in the generic type or method. Connect and share knowledge within a single location that is structured and easy to search. CS8624 - Argument cannot be used as an output due to differences in the nullability of reference types. In MVC? Or you could call .ToList() on the enumerable. To answer you question, I think that yes you should call ToList before returning the enumeration mainly because your IEnumerable could be an EF query and there's no way for the user of your class to know this, meaning the person could use this enumeration multiple times and launch tons of SQL queries without knowing it (until there would be performance problems and diagnostic would lead to that IEnumerable launching queries). IEnumerable is an interface contained in the System.Collections.Generic namespace. Confining signal using stitching vias on a 2 layer PCB, Lateral loading strength of a bicycle wheel, Options to insulate basement electric panel, Looking for advice repairing granite stair tiles. Enumerable.Cast<TResult>(IEnumerable) Method (System.Linq) @dusky this makes sense, but remember that. The runtime type of the elements in the collection must match the target type, or in the case of value types, the runtime type of elements must be the result of a boxing conversion of the target type. The type to cast the elements of source to. The method ToList() has one parameter only. Do you need your, CodeProject, Not the answer you're looking for? 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 IEnumerable to create a List from. The correct syntax to use this method is as follows Enumerable.ToList(source); The method ToList () has one parameter only. The ToList() method in C# is an alternate method to manipulate these data. The performance cost of using ToList is the same as using new List<>([your enumerable]) constructor, which is an O(n) operation since you need to copy the whole array. You shouldn't care about what the caller does with it, because the return type clearly states what the returned value is capable of doing. Returning an IQueryable as an IEnumerable or List will be no different WRT how many times the query is executed. Cannot convert list to Ienumerable in mvc - C# Corner here we go Whether or not he'll run into concurrency issues highly depends on what he's exposing/doing with the results. Why do most languages use the same token for `EndIf`, `EndWhile`, `EndFunction` and `EndStructure`? Do large language models know what they are talking about? Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<T>' to 'Microsoft.AspNetCore.Mvc.ActionResult<System.Collections.Generic.IEnumerable<T>> aspnet/Mvc#8061 rcollette mentioned this issue on Jul 23, 2018 Limitation of ActionResult<T> not mentioned dotnet/AspNetCore.Docs#7777 msftbot bot locked as on Dec 3, 2019 So he needs to just use var. In C#, an IEnumerable can be converted to a List through the following lines of code: IEnumerable enumerable = Enumerable.Range(1, 300); List asList = enumerable.ToList(); To achieve the same result in UiPath: Create a List<> variable to store the List. The correct syntax to use this method is as follows. Flutter change focus color and icon color but not works. An IEnumerable backed by a database should not be lazily evaluated, as the connection it was bound to can potentially be closed by the time it is enumerated. 'System.Collections.Generic.IEnumerable', 'System.Collections.Generic.List', //List to store enemies already hit by this chain jump, //List to store enemies that can be jumped to, (You must log in or sign up to reply here. More info about Internet Explorer and Microsoft Edge. [Solved] Cannot implicitly convert type 'task<ienumerable Why are lights very bright in most passenger trains, especially at night? How do laws against computer intrusion handle the modern situation of devices routinely being under the de facto control of non-owners? Hi! results.Cast (Of String) ().ToList ()? ). 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. Return an IEnumerable. See also immutable list. To get things working you just need to change the return type of your GetHistory() method to List<URL>. IEnumerable to List C #, What is the best way to get this data?