Dictionary.Item [] C＃のプロパティ

C＃のDictionary.Item []プロパティは、ディクショナリで指定されたキーに関連付けられた値を取得または設定するために使用されます。

構文

以下は構文です-

public TValue this[TKey key] { get; set; }

例

ここで、Dictionary.Item[]プロパティを実装する例を見てみましょう-

using System;
using System.Collections.Generic;
public class Demo {
   public static void Main(){
      Dictionary<string, string> dict =
      new Dictionary<string, string>();
      dict.Add("One", "Chris");
      dict.Add("Two", "Steve");
      dict.Add("Three", "Messi");
      dict.Add("Four", "Ryan");
      dict.Add("Five", "Nathan");
      Console.WriteLine("Count of elements = "+dict.Count);
      Console.WriteLine("\nKey/value pairs...");
      foreach(KeyValuePair<string, string> res in dict){
         Console.WriteLine("Key = {0}, Value = {1}", res.Key, res.Value);
      }
      Console.WriteLine("Value for key three = "+dict["Three"]);
      dict["Three"] = "Ronaldo";
      Console.Write("Updated value associated with key Three...");
      Console.WriteLine(dict["Three"]);
      if (dict.ContainsValue("Angelina"))
         Console.WriteLine("\n\nValue found!");
      else
         Console.WriteLine("\n\nValue isn't in the dictionary!");
      dict.Clear();
      Console.WriteLine("Cleared Key/value pairs...");
      foreach(KeyValuePair<string, string> res in dict){
         Console.WriteLine("Key = {0}, Value = {1}", res.Key, res.Value);
      }
      Console.WriteLine("Count of elements now = "+dict.Count);
   }
}

出力

これにより、次の出力が生成されます-

Count of elements = 5
Key/value pairs...
Key = One, Value = Chris
Key = Two, Value = Steve
Key = Three, Value = Messi
Key = Four, Value = Ryan
Key = Five, Value = Nathan
Value for key three = Messi
Updated value associated with key Three...Ronaldo
Value isn't in the dictionary!
Cleared Key/value pairs...
Count of elements now = 0

例

ここで、Dictionary.Item[]メソッドを実装する別の例を見てみましょう-

using System;
using System.Collections.Generic;
public class Demo {
   public static void Main(){
      Dictionary<string, string> dict =
      new Dictionary<string, string>();
      dict.Add("One", "Chris");
      dict.Add("Two", "Steve");
      dict.Add("Three", "Messi");
      dict.Add("Four", "Ryan");
      dict.Add("Five", "Nathan");
      Console.WriteLine("Count of elements = "+dict.Count);
      Console.WriteLine("\nKey/value pairs...");
      foreach(KeyValuePair<string, string> res in dict){
         Console.WriteLine("Key = {0}, Value = {1}", res.Key, res.Value);
      }
      Console.WriteLine("Value for key three = "+dict["Three"]);
      dict["Three"] = "Katie";
      Console.Write("Updated value associated with key Three...");
      Console.WriteLine(dict["Three"]);
   }
}

出力

これにより、次の出力が生成されます-

Count of elements = 5
Key/value pairs...
Key = One, Value = Chris
Key = Two, Value = Steve
Key = Three, Value = Messi
Key = Four, Value = Ryan
Key = Five, Value = Nathan
Value for key three = Messi
Updated value associated with key Three...Katie