小编A19*_*919的帖子

声明：

(definitions != null && definitions.Where(key => key.asset_id != null &&
                                          key.asset_id == item).FirstOrDefault() != null

投掷：

集合被修改，枚举操作可能无法执行

如何解决这个问题？

if (definitions != null 
    && definitions
         .Where(key => key.asset_id != null && key.asset_id == item)
         .FirstOrDefault() != null)
{
    CurrentDuration = definitions
                        .Where(key => key.asset_id != null && key.asset_id == item)
                        .FirstOrDefault().duration;
}

如何启用内容可见性？为什么它不可见？

<div class="header"></div>
<div class="categories"></div>
<div class="content"></div>

CSS样式:

body {
  margin: 0;
  padding: 0;
}
.header {
  padding-top: 0;
  margin-top: 0;
  height: 160px;
  background: #666;
}
.categories {
  position: absolute;
  height: 100%;
  width: 20%;
  background: #b6fd40;
}
.content {
  height: 100%;
  width: 100%;
  background: gray;
}

小提琴.

例如,让我有这样的事情.

public enum CarEnum { BWM, LadaKalina };

    class Program
    {
        static void Main(string[] args)
        {
            var carEnum = CarEnum.LadaKalina;
            GetMessage(carEnum);
        }
        public static void GetMessage(CarEnum carEnum)
        {
            switch (carEnum)
            {
                case CarEnum.BWM:
                    Console.WriteLine("BWM");
                    break;
                case CarEnum.LadaKalina:
                    Console.WriteLine("LadaKalina");
                    break;
                default:
                    Console.WriteLine("default");
                    break;
            }
        }
    }

我想在函数GetMessage中调用默认情况.通过论证更好的是什么？

是)我有的:

1. 25686-47362-04822-08149-48999-28161-15124-63556

2. 25686-47362-04822-08149-48999-28161-15124-6355654534

3. 54354325686-47362-04822-08149-48999-28161-15124-63556

4. 25686-47362-04822-08149-48999-28161-15124-6355654534fds

5. fdsfds54354325686-47362-04822-08149-48999-28161-15124-63556

6. 25686-47362-04822-08149-48999-28161-15124-63556-63556

我希望得到什么

1. 25686-47362-04822-08149-48999-28161-15124-63556

我尝试了最近的东西 ([0-9]{5,5}){8}

我试图避免2,3,4,5,6.

我在面试任务中找到了这段代码.结果取决于调试.为什么Value改变调试模式？请解释它是如何工作的.

static IEnumerable<int> Square(IEnumerable<int> a)
{
    foreach (var r in a)
    {
        Console.WriteLine(r * r);
        yield return r * r;
    }
}
class Wrap
{
    private static int init = 0;
    public int Value1
    {
        get { return ++init; }
    }
}

static void Main(string[] args)
{
    var w = new Wrap();
    var wraps = new Wrap[3];
    for (int i = 0; i < wraps.Length; i++)
    {
        wraps[i] = w;
    }
    var values = wraps.Select(x => x.Value1);
    var …

为什么要List<Component> l = second.ToList();导致

System.NullReferenceException'发生在ConsoleApplication1.exe中

在 select new { id = b.id, Name = b.Name };

如何解决这个问题？

namespace ConsoleApplication1
{
class Program
{
    static void Main(string[] args)
    {
        List<Component> firstlist = new List<Component>();
        List<Component> secondlist = new List<Component>();
        List<Component> thirdlist = new List<Component>();

        firstlist.Add(new Component { id = 1, Name = "Jhon" });
        secondlist.Add(new Component { id = 2, Name = "Jhon" });
        thirdlist.Add(new Component { id = 3, Name = "Jhon" });

        var first = from d …

我是C++领域的新手,面对双指针.问题是如何设置x=5功能test？

#include <iostream>
using namespace std;

typedef struct _DoublePointer
{
    int x;
    int y;
} DoublePointer;

void test(_DoublePointer** pointer)
{

}

void main()
{
    _DoublePointer* pointer = new _DoublePointer;
    _DoublePointer** doublePointer = &pointer;
    test(doublePointer);
}