ienumerable

问题 I have a model which has an IEnumerable property (warning pseudo-code to follow) public class PersonModel { public string Name { get; set; } public IEnumerable<AddressModel> Addresses { get; set; } } public class AddressModel { public string Name { get; set; } } I want to display the Address sub-objects in the same view Person.cshtml @model PersonModel <form> <h2>Person</h2> @Html.EditorFor(m=>m.Name) <ul>@Html.EditorFor(m=>m.Addresses)</ul> </form> EditorTemplate/AddressModel @model

问题 I wrote a LINQ extension method SplitBetween analogous to String.Split . > new List<int>(){3,4,2,21,3,2,17,16,1} > .SplitBetween(x=>x>=10) [3,4,2], [3,2], [], [1] Source: // partition sequence into sequence of contiguous subsequences // behaves like String.Split public static IEnumerable<IEnumerable<T>> SplitBetween<T>(this IEnumerable<T> source, Func<T, bool> separatorSelector, bool includeSeparator = false) { var l = new List<T>(); foreach (var x in source) { if (separatorSelector(x)) { if

问题 All string.Split methods seems to return an array of strings ( string[] ). I'm wondering if there is a lazy variant that returns an IEnumerable<string> such that one for large strings (or an infinite length IEnumerable<char> ), when one is only interested in a first subsequences, one saves computational effort as well as memory. It could also be useful if the string is constructed by a device/program (network, terminal, pipes) and the entire strings is thus not necessary immediately fully

问题 I'm using a linq query to output an int array. But I need to pass this into a method that only accepts int?[]. So after searching on ways to convert int[] to int?[] I found something that seemed might work here The following code is a simplified example that shows what is working and not working. using System; using System.Collections.Generic; using System.Web; using System.Linq; namespace ConsoleApp { class Program { static void Main(string[] args) { // working... int[] vids1 = new[] { "",

问题 In 8.8.4 of the C# specification, it provides this example: A foreach statement of the form foreach (V v in x) embedded-statement is then expanded to: { E e = ((C)(x)).GetEnumerator(); try { V v; while (e.MoveNext()) { v = (V)(T)e.Current; embedded-statement } } finally { … // Dispose e } } It also says: The iteration variable corresponds to a read-only local variable with a scope that extends over the embedded statement. The variable v is read-only in the embedded statement. How is the

问题 Does there exist a standard pattern for yield returning all the items within an Enumerable? More often than I like I find some of my code reflecting the following pattern: public IEnumerable<object> YieldReturningFunction() { ... [logic and various standard yield return] ... foreach(object obj in methodReturningEnumerable(x,y,z)) { yield return obj; } } The explicit usage of a foreach loop solely to return the results of an Enumerable reeks of code smell to me. Obviously I could abandon the

问题 I have an IEnumerable<string> , which is "streamed" per yield statements from a method. Now I want to convert this enumerable to a Stream to use it as streamed result. Any ideas how I can do this? What I finally want to do is to return the Stream as FileStreamResult from an ASP.NET controller action. This result should be streamed as download to the client. What I do NOT want to do is to write the whole content of the IEnumerable to the stream before I return the result. This would eliminate

问题 Like two overlapping line segments, we can find infinite points of intersection. To enumerate all these points might not make sense, and we might just want to present that this collection is infinity. Floating point numbers have defined NegativeInfinity and PositiveInfinity . A number which represents count or ordinal seem not necessary to use floating point numbers, however, integers are not defined something to represent infinity. So I tried to implement an infinite enumerable. But I

问题 So basically i have this method. public List<Customer> FilterCustomersByStatus(List<Customer> source, string status) { return (List<Customer>)source.Where(c => c.Status == status); } I throws me an error that it cannot cast: Unable to cast object of type 'WhereListIterator`1[AppDataAcces.Customer]' to type 'System.Collections.Generic.List`1[AppDataAcces.Customer]'. Why...? since the underlying type is the same, does the Enumerable.Where create a new instance of WhereListIterator and if so why

问题 So basically i have this method. public List<Customer> FilterCustomersByStatus(List<Customer> source, string status) { return (List<Customer>)source.Where(c => c.Status == status); } I throws me an error that it cannot cast: Unable to cast object of type 'WhereListIterator`1[AppDataAcces.Customer]' to type 'System.Collections.Generic.List`1[AppDataAcces.Customer]'. Why...? since the underlying type is the same, does the Enumerable.Where create a new instance of WhereListIterator and if so why