如何使用 C# 遍历 Dictionary<string, object>

Question

我有一个

Dictionary<string, List<string>> demo = new Dictionary<string, List<string>>();

List<String> key1val= new List<string>();
key1val.Add("1");
key1val.Add("2");
key1val.Add("3");

List<String> key2val= new List<string>();
key2val.Add("4");
key2val.Add("5");

demo.Add("key1", key1val);
demo.Add("key2", key2val);

foreach (var item in demo)
{
    foreach(var it in item.Value)
    {
        Console.WriteLine(it);
    }
}

我想遍历所有键，例如 key1,key2。

如果当前项是 key1，那么内部循环应该获取关于 key1 的所有值并将其迭代到第二个循环

loop
iterate though key1
iterate though [1,2,3] 

loop
iterate though key2
iterate though [4,5]

Answer 1

foreach (var item in demo )
{
   WriteLine("loop");
   WriteLine($"iterate though {item.key}");
   WriteLine($"iterate though {item.Value}");
   WriteLine();
}

这应该输出你想要的但是，您可以：

foreach (var item in demo )
{
   WriteLine("loop");
   WriteLine($"iterate though {item.key}");
   if (item.Value is IEnumerable<string> val) foreach(var v in val) WriteLine(v);
   WriteLine();
}

Answer 2

嗯，使用 2 个嵌套循环。

外层遍历键，内层遍历相应条目的值：

Dictionary<string, List<string>> demo = new Dictionary<string, List<string>>();

List<String> key1val= new List<string>();
key1val.Add("1");
key1val.Add("2");
key1val.Add("3");

List<String> key2val= new List<string>();
key2val.Add("4");
key2val.Add("5");

demo.Add("key1", key1val);
demo.Add("key2", key2val);

foreach (var key in demo.Keys)
{
    Console.WriteLine(key);
    foreach (var elem in demo[key])
    {
        Console.WriteLine(elem);
    }
}

这输出

key1
1
2
3
key2
4
5

Answer 3

使用 LINQ SelectMany 将值累积到单个列表中：

foreach (string value in demo.SelectMany(kvp => kvp.Value))
{
    Console.WriteLine(val);
}

Answer 4

foreach (var item in demo)
{
    Console.WriteLine("loop");
    Console.WriteLine($"iterate though {item.Key}");
    var valueAsString = $"[{String.Join(",", item.Value)}]";
    Console.WriteLine($"iterate though {valueAsString}");
}

输出：

loop
iterate though key1
iterate though [1,2,3]

loop
iterate though key2
iterate though [4,5]

您可以测试：https://dotnetfiddle.net/REqIdD

Answer 5

Linq 解决方案包括 Concat 将 Key 和 Values 组合成一个单个集合SelectMany 扁平化 他们：

Dictionary<string, List<string>> demo = ...

var result = demo
  .SelectMany(pair => new string[] { pair.Key }.Concat(pair.Value));  

// Let's have a look
foreach (var item in result)
  Console.WriteLine(item);

如何使用 C# 遍历 Dictionary<string, object>

How to iterate through Dictionary<string, object> using c#

c#

foreach

dictionary

c#-4.0