Question

c#如何为foreach语句中的空值赋值？

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
//Program mytest = new Program();
//Console.WriteLine(testing());

testing();
}

private static string testing()
{
//string sum = "";
string[] arr = new string[5];
arr[1] = "5";
arr[3] = "51";
arr[4] = "52";
foreach (string i in arr)
{
if (i=="")
{
i="空";
}

Console.WriteLine(i);

}
//return sum;
return arr.ToString();
}
}
}

调试的结果出错
提示为：“i是一个foreach变量，无法为它赋值”

Answer 1

foreach中不可对正在迭代的变量赋值

改成

for (int i = 0; i < arr.Length; i++)
{
if (arr[i] == "")
arr[i] = "空";
}

Answer 2

//你可以用for代替foreach
private static string testing()
{
//string sum = "";
string[] arr = new string[5];
arr[1] = "5";
arr[3] = "51";
arr[4] = "52";
for (int i=0;i<arr.Length;i++)
{
if (string.IsNullOrWhiteSpace(arr[i]))
{
arr[i] = "空";
}
Console.WriteLine(arr[i]);

}
//return sum;
return arr.ToString();
}

Answer 3

问题关键出在，你给 i 赋值，提示的已经很清楚了，
foreach中不可对正在迭代的变量赋值@Raiuy，是正解。
这种情况的正确做法，应该是用for循环，@涐会 的做法最好

Answer 4

经过的风格

Answer 5

i是个数组的下标 你怎么能给他赋值呢