如何检查字典是否包含列表中的项目

Question

如何检查字典是否包含列表中的项目。 我有以下字典和以下列表：

public static List<string> DixieStatesList = new List<string>
        {
            "Alabama", "Arkansas", "Floryda", "Georgia", "KarolinaPołudniowa", "KarolinaPółnocna",
            "Kentucky", "Luizjana", "Mississippi", "Missouri", "Oklahoma", "Teksas", "Tennesee", "Wirginia",
            "WirginiaZachodnia"
        };

public static Dictionary<string, float> WallaceNPPFRpopularities = new Dictionary<string, float>()
        {
            {"Alabama", 6}, {"Alaska", 2}, {"Arizona", 1}, {"Arkansas", 4}, {"Connecticut", 2},
            {"DakotaPołudniowa", 5}, {"DakotaPółnocna", 5}, {"Delaware", 4}, {"Floryda", 4},
            {"Georgia",  6}, {"Idaho", 1.5f}, {"Illinois", 2}, {"Indiana", 5}, {"Iowa", 2},
            {"Kalifornia", 4}, {"Kansas", 5}, {"KarolinaPołudniowa", 6}, {"KarolinaPółnocna", 5},
            {"Kentucky", 3}, {"Kolorado", 3}, {"Luizjana", 4}, {"Maine", 6}, {"Maryland", 5},
            {"Massachusets", 2 }, {"Michigan", 5}, {"Minnesota", 1.5f}, {"Mississippi", 6},
            {"Missouri", 2}, {"Montana", 1.5f}, {"Nebraska", 2}, {"Nevada", 4}, {"NewHampshire", 2},
            {"NewJersey", 4}, {"NowyJork", 1.5f}, {"NowyMeksyk", 2}, {"Ohio", 4}, {"Oklahoma", 4},
            {"Oregon", 1}, {"Pensylwania", 1.5f}, {"RhodeIsland", 3}, {"Teksas", 4}, {"Tennesee", 4},
            {"Utah", 1.5f}, {"Vermont", 5}, {"Waszyngton", 1}, {"Wirginia", 6}, {"WirginiaZachodnia", 6},
            {"Wisconsin", 1.5f}, {"Wyoming", 2}
        };

我想使用'foreach'或'if'或两者来检查这个字典是否包含列表中的一个元素并最终改变字典中元素的值，它与列表中的元素具有相同的键0.25 F。

Answer 1

我在 c# 之前从未接触过，但你想要那样的东西。 而且我不认为您可以更改静态字典，但是，如果它不是静态的，这是一种方法：

foreach(string key in DixieStatesList){

if(WallaceNPPFRpopularities.ContainsKey(key)
    WallaceNPPFRpopularities[key] =+ 0.25;

}

Answer 2

您可以使用Enumerable.Intersect 方法：

const float Increment = .25f;
foreach (string state in WallaceNPPFRpopularities.Keys.Intersect(DixieStatesList))
{
    WallaceNPPFRpopularities[state] += Increment;

    // Incremented "Alabama" popularity to 6.25.
    // Incremented "Arkansas" popularity to 4.25.
    // Incremented "Floryda" popularity to 4.25.
    // Incremented "Georgia" popularity to 6.25.
    // Incremented "KarolinaPołudniowa" popularity to 6.25.
    // Incremented "KarolinaPółnocna" popularity to 5.25.
    // Incremented "Kentucky" popularity to 3.25.
    // Incremented "Luizjana" popularity to 4.25.
    // Incremented "Mississippi" popularity to 6.25.
    // Incremented "Missouri" popularity to 2.25.
    // Incremented "Oklahoma" popularity to 4.25.
    // Incremented "Teksas" popularity to 4.25.
    // Incremented "Tennesee" popularity to 4.25.
    // Incremented "Wirginia" popularity to 6.25.
    // Incremented "WirginiaZachodnia" popularity to 6.25.
    Console.WriteLine(@$"Incremented ""{state}"" popularity to {WallaceNPPFRpopularities[state]}.");
}

Answer 3

您可以简单地使用 Dictionary 上的 ContainsKey 来测试键是否存在，如果存在则使用索引获取结果。

        float result = -1;

        if(WallaceNPPFRpopularities.ContainsKey("Alaska"))
        {
            result = WallaceNPPFRpopularities["Alaska"];
        }

Answer 4

尝试这个

    foreach (var key in DixieStatesList)
    {
        if (WallaceNPPFRpopularities.ContainsKey(key))
            WallaceNPPFRpopularities[key] += 0.25f;
    }