Question

我有一个 Dictionary<string, string>[] 数组，其中每个元素都是一个 Dictionary<string, string>，具有相同的键和不同的值。

如何为给定的 Key 和 Value 获取对象的索引？

例如，如果字典数组有两个元素为：

    [0]: {'Key1', 'ValueA}
         {'Key2', 'ValueB}
    [1]: {'Key1', 'ValueC}
         {'Key2', 'ValueD}

如何获取'Key2' = 'ValueD'的索引？因此，索引结果 = 1。

Answer 1

您可以使用以下 LINQ 查询，它就像一个尽快中断的循环：

int index = dictionaries
    .Select((dict, index) => (dict, index)) // put the dictionary and it's index in a ValueTuple
    .Where(x => x.dict.Any(kv => kv.Key == "Key2" && kv.Value == "ValueD")) // filter by key & value
    .Select(x => x.index) // select the index
    .DefaultIfEmpty(-1)   // if no dictionary met the condition you want -1 as result
    .First(); // this is safe, you get either a single index or -1 as fallback

但请注意，您的方法正在失去字典的快速查找功能。

编辑：Somebody's approach 效率更高，您可以将其与此结合使用：

int index = dictionaries
    .Select((dict, index) => (dict, index)) // put the dictionary and it's index in a ValueTuple
    .Where(x => x.dict.TryGetValue("Key2", out string value) && value == "ValueD") // filter by key & value
    .Select(x => x.index) // select the index
    .DefaultIfEmpty(-1) // if no dictionary met the condition you want -1 as result
    .First(); // this is safe, you get either a single index or -1 as fallback

Answer 2

在这个解决方案中，在每个字典中搜索给定值是 O(1) 而不是其他解决方案中的 O(n)：

string expectedKey = "Key2";
string expectedValue = "ValueD";
var item = array.FirstOrDefault(x => x.TryGetValue(expectedKey , out string value) && value == expectedValue);
if(item == null)
{
   Console.WriteLine("entry wasn't found in any dictionary");
   return;
}
int index = Array.IndexOf(array, item);

Answer 3

var item = array.Where(x=>x.Any(y=>y.Key == "Key2" && y.Value == "ValueD")).First();

var index = array.IndexOf(item);

从给定键和值的字典数组中获取字典索引

3 个答案: