从数组中获取键的方法

Question

这个PHP脚本的等效C#语法是什么？:

<?php
$arr = array("linux", "windows", "linux", "linux", "windows", "mac os", "unix", "mac os");
$unique = array_unique($arr);
foreach($unique as $key=>$value){
    echo $key."\n";
}
?>

上面代码的结果是:

0
1
5
6

因此,删除数组的副本,然后显示数组的键.我只能显示数组的值:

string[] arr = { "linux", "windows", "linux", "linux", "windows", "mac os", "unix", "mac os" };
string[] uniq = arr.Distinct().ToArray();
foreach (string unik in uniq)
{
    textBox1.AppendText(unik+"\r\n");
}

Answer 1

你可以很容易地使用Linq做到这一点:

var indices = arr.Distinct()
                 .Select(s => Array.IndexOf(arr,s));

foreach (int i in indices)
{
    textBox1.AppendText(i+"\r\n");
}

或包括值和索引:

var indices = arr.Distinct()
                 .Select(s => new {s, i = Array.IndexOf(arr,s)});

foreach (var si in indices)
{
    textBox1.AppendText(string.Format({0}: {1}\n", si.i, si.s));
}

如果性能是一个问题,那么更高效(虽然难以理解)的版本将是:

var indices = arr.Select((s, i) => new {s, i})  // select the value and the index
                 .GroupBy(si => si.s)           // group by the value
                 .Select(g => g.First());       // get the first value and index

foreach (var si in indices)
{
    textBox1.AppendText(string.Format({0}: {1}\n", si.i, si.s));
}