检查集合为空或不 [英] Check if collection is empty or not

问题描述

public ActionResult Create(FormCollection collection, FormCollection formValue)
{
    try
    {
        Project project = new Project();

        TryUpdateModel(project, _updateableFields);

        var devices = collection["devices"];
        string[] arr1 = ((string)devices).Split(',');
        int[] arr2 = Array.ConvertAll(arr1, s => int.Parse(s));

        project.User = SessionVariables.AuthenticatedUser;
        var time = formValue["Date"];
        project.Date = time;
        project.SaveAndFlush();

        foreach (int i in arr2)
        {
            Device d = Device.Find(i);
            d.Projects.Add(project);
            d.SaveAndFlush();
        }

        return RedirectToAction("Index");
    }
    catch (Exception e)
    {
        return View(e);
    }
}

我想换行的foreach中，检查是否

I want to wrap the foreach in a if statement which checks if

var devices = collection["devices"];

为空或不是。如果它的每个空的，不应被执行。根据记录，收集[设备]是复选框值的集合，从一种形式。

is empty or not. If its empty the for each should not be executed. For the record, collection["devices"] is a collection of checkbox values from a form.

推荐答案

您不需要检查，如果集合为空，如果是空的ForEach内code将不会被执行，看我下面的例子

You do not need to check if the collection is empty, if it is empty the code inside the ForEach will not be executed, see my example below.

using System;
using System.Collections.Generic;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> emptyList = new List<string>();

            foreach (string item in emptyList)
            {
                Console.WriteLine("This will not be printed");
            }

            List<string> list = new List<string>();

            list.Add("item 1");
            list.Add("item 2");

            foreach (string item in list)
            {
                Console.WriteLine(item);
            }

            Console.ReadLine();
        }
    }
}

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