在使用 linq 列舉 Hashset 之前如何查找計數？如果計數為零，我想回傳空 代碼小提琴
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
private static HashSet<string> signalsobject = new HashSet<string>();
public enum Signals : long
{
SHORT20EMASIGNAL = 2 ^ 7,
DOUBLESHORTSIGNAL = 2 ^ 8,
}
;
public static void Main()
{
signalsobject.Add(Signals.SHORT20EMASIGNAL.ToString());
signalsobject.Add(Signals.SHORT20EMASIGNAL.ToString());
signalsobject.Remove(Signals.SHORT20EMASIGNAL.ToString());
Console.WriteLine(signalsobject.Count);
Console.WriteLine(signalsobject.Aggregate((a, b) => a " " b));
//Console.WriteLine(signalsobject.ToString());
// string a = signalsobject.Count>0? (signalsobject.Aggregate((a, b) => a " " b)): "Empty";
}
}
我目前在 Program.Main() 的 System.Linq.Enumerable.Aggregate[TSource](IEnumerable 1 source, Func3 func) 得到 [System.InvalidOperationException: Sequence contains no elements]：第 21 行
uj5u.com熱心網友回復：
像這樣？信號物件.Aggregate("", (a, b) => a " " b)
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