WebDec 30, 2014 · If you want your ForEach extension to throw when called for null enumerables, you can just leave the null check away, and call it with the same elvis syntax as the List's version: myPossiblyNullEnumerable?.ForEach (i => ...); Share Follow answered Nov 16, 2024 at 13:34 Riikka Heikniemi 193 1 8 Add a comment Your Answer WebDec 2, 2024 · One of the use cases of the null-forgiving operator is in testing the argument validation logic. For example, consider the following class: C# #nullable enable public class Person { public Person(string name) => Name = name ?? throw new ArgumentNullException (nameof(name)); public string Name { get; } }
C# – Shorten null check around foreach loops - Jon Schneider
WebSep 24, 2013 · I'm asking what is the reasoning for throwing an exception when the object that you are trying to iterate over with a foreach loop is null? For example, the following code throws an exception: public void Test () { IEnumerable numbers = null; foreach (var number in numbers) { //Do stuff } } Now the fix is easy enough, just check for null ... WebJan 17, 2024 · If you have a nullable that doesn't have a value, and you try to ask it for it's value, you get this exception: Make sure your p.StartYear nullable has a value, or check for p.HasValue and only run your loop if it's true. 1 - The variable "year" must be a List, and not a simple Int. You can replace the declaration "int year = " to "var year = "; db2 case when 多条件
C# 有效地从
WebJul 30, 2012 · C# 8 could simply have a null-conditional foreach of some sort, i.e. syntax like this: foreach? (var i in collection) { } I think it's a common enough scenario to justify … WebJan 4, 2024 · Unfortunately, this means changing the language and issuing a warning when you assign null (string text = null, for example) or assign a nullable reference type (such as string? text = null; string moreText = text;). The first of … WebMay 23, 2024 · using System.Collections; using System.Collections.Generic; public static class IsNullOrEmptyExtension { public static bool IsNullOrEmpty (this IEnumerable source) { if (source != null) { foreach (object obj in source) { return false; } } return true; } public static bool IsNullOrEmpty (this IEnumerable source) { if (source != null) { foreach (T … db2 backup history command