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法律研究C# 中的 Dictionary.ContainsKey() 方法
C# 中的 Dictionary.ContainsKey() 方法檢查 Dictionary<TKey, TValue< 是否有指定鍵。
語法
public bool ContainsKey (TKey key);
上面，引數鍵是要查詢的鍵。
現在讓我們看一個實現 Dictionary.ContainsKey() 方法的示例 −
示例
using System;
using System.Collections.Generic;
public class Demo {
public static void Main(){
Dictionary<string, string> dict =
new Dictionary<string, string>();
dict.Add("One", "John");
dict.Add("Two", "Tom");
dict.Add("Three", "Jacob");
dict.Add("Four", "Kevin");
dict.Add("Five", "Nathan");
Console.WriteLine("Count of elements = "+dict.Count);
Console.WriteLine("
Key/value pairs...");
foreach(KeyValuePair<string, string> res in dict){
Console.WriteLine("Key = {0}, Value = {1}", res.Key, res.Value);
}
if (dict.ContainsKey("Three"))
Console.WriteLine("Key found!");
else
Console.WriteLine("Key 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);
}
}輸出
這將產生以下輸出 −
Count of elements = 5 Key/value pairs... Key = One, Value = John Key = Two, Value = Tom Key = Three, Value = Jacob Key = Four, Value = Kevin Key = Five, Value = Nathan Key found! Cleared Key/value pairs... Count of elements now = 0
現在讓我們看另一個實現 Dictionary.ContainsKey 屬性的示例 −
示例
using System;
using System.Collections.Generic;
public class Demo {
public static void Main(){
Dictionary<string, string> dict =
new Dictionary<string, string>();
dict.Add("One", "John");
dict.Add("Two", "Tom");
dict.Add("Three", "Jacob");
dict.Add("Four", "Kevin");
dict.Add("Five", "Nathan");
Console.WriteLine("Count of elements = "+dict.Count);
Console.WriteLine("
Key/value pairs...");
foreach(KeyValuePair<string, string> res in dict){
Console.WriteLine("Key = {0}, Value = {1}", res.Key, res.Value);
}
if (dict.ContainsKey("mykey"))
Console.WriteLine("Key found!");
else
Console.WriteLine("Key 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);
}
}輸出
這將產生以下輸出 −
Count of elements = 5 Key/value pairs... Key = One, Value = John Key = Two, Value = Tom Key = Three, Value = Jacob Key = Four, Value = Kevin Key = Five, Value = Nathan Key isn't in the dictionary! Cleared Key/value pairs... Count of elements now = 0
更新於: 2019-11-04
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