我看到了一些不同的方法来迭代C#中的字典。有标准的方法吗?


当前回答

除了在使用

foreach(KeyValuePair<string, string> entry in myDictionary)
{
    // do something with entry.Value or entry.Key
}

or

foreach(var entry in myDictionary)
{
    // do something with entry.Value or entry.Key
}

最完整的是以下内容,因为您可以从初始化中看到字典类型,kvp是KeyValuePair

var myDictionary = new Dictionary<string, string>(x);//fill dictionary with x

foreach(var kvp in myDictionary)//iterate over dictionary
{
    // do something with kvp.Value or kvp.Key
}

其他回答

C#7.0引入了解构器,如果您正在使用.NET Core 2.0+应用程序,那么结构KeyValuePair<>已经为您提供了一个解构器()。因此,您可以做到:

var dic = new Dictionary<int, string>() { { 1, "One" }, { 2, "Two" }, { 3, "Three" } };
foreach (var (key, value) in dic) {
    Console.WriteLine($"Item [{key}] = {value}");
}
//Or
foreach (var (_, value) in dic) {
    Console.WriteLine($"Item [NO_ID] = {value}");
}
//Or
foreach ((int key, string value) in dic) {
    Console.WriteLine($"Item [{key}] = {value}");
}

取决于你是在寻找关键点还是值。。。

来自MSDN Dictionary(TKey,TValue)类描述:

// When you use foreach to enumerate dictionary elements,
// the elements are retrieved as KeyValuePair objects.
Console.WriteLine();
foreach( KeyValuePair<string, string> kvp in openWith )
{
    Console.WriteLine("Key = {0}, Value = {1}", 
        kvp.Key, kvp.Value);
}

// To get the values alone, use the Values property.
Dictionary<string, string>.ValueCollection valueColl =
    openWith.Values;

// The elements of the ValueCollection are strongly typed
// with the type that was specified for dictionary values.
Console.WriteLine();
foreach( string s in valueColl )
{
    Console.WriteLine("Value = {0}", s);
}

// To get the keys alone, use the Keys property.
Dictionary<string, string>.KeyCollection keyColl =
    openWith.Keys;

// The elements of the KeyCollection are strongly typed
// with the type that was specified for dictionary keys.
Console.WriteLine();
foreach( string s in keyColl )
{
    Console.WriteLine("Key = {0}", s);
}

有很多选择。我个人最喜欢的是KeyValuePair

Dictionary<string, object> myDictionary = new Dictionary<string, object>();
// Populate your dictionary here

foreach (KeyValuePair<string,object> kvp in myDictionary)
{
     // Do some interesting things
}

您也可以使用键和值集合

正如在这个答案中已经指出的,KeyValuePair<TKey,TValue>实现了一个从.NET Core 2.0、.NET Standard 2.1和.NET Framework 5.0(预览版)开始的解构方法。

这样,就可以以KeyValuePair不可知的方式遍历字典:

var dictionary = new Dictionary<int, string>();

// ...

foreach (var (key, value) in dictionary)
{
    // ...
}

如果要使用for循环,可以执行以下操作:

var keyList=new List<string>(dictionary.Keys);
for (int i = 0; i < keyList.Count; i++)
{
    var key= keyList[i];
    var value = dictionary[key];
}