.NET C#: NameValueCollection
11516 ワード
NameValueCollection class is in System.Collection.Specialized assembly.
Unlike with HashTable, NameValueCollection can have more than one values for one key.
So there is no error for code below:
NameValueCollection myCol = new NameValueCollection();
myCol.Add("red", "rojo");
myCol.Add("red", "rouge");
while using HashTable there will be an error.
Let us see some demo:
reference: https://msdn.microsoft.com/zh-cn/library/system.collections.specialized.namevaluecollection.aspx
Unlike with HashTable, NameValueCollection can have more than one values for one key.
So there is no error for code below:
NameValueCollection myCol = new NameValueCollection();
myCol.Add("red", "rojo");
myCol.Add("red", "rouge");
while using HashTable there will be an error.
Let us see some demo:
1 using System;
2 using System.Collections;
3 using System.Collections.Specialized;
4
5 public class ConsoleTest
6 {
7
8 public static void Main()
9 {
10
11 // Creates and initializes a new NameValueCollection.
12 NameValueCollection myCol = new NameValueCollection();
13 myCol.Add("red", "rojo");
14 myCol.Add("green", "verde");
15 myCol.Add("blue", "azul");
16 myCol.Add("red", "rouge");
17
18 // Displays the values in the NameValueCollection in two different ways.
19 Console.WriteLine("Displays the elements using the AllKeys property and the Item (indexer) property:");
20 PrintKeysAndValues(myCol);
21 Console.WriteLine("Displays the elements using GetKey and Get:");
22 PrintKeysAndValues2(myCol);
23
24 // Gets a value either by index or by key.
25 Console.WriteLine("Index 1 contains the value {0}.", myCol[1]);
26 Console.WriteLine("Key \"red\" has the value {0}.", myCol["red"]);
27 Console.WriteLine();
28
29 // Copies the values to a string array and displays the string array.
30 String[] myStrArr = new String[myCol.Count];
31 myCol.CopyTo(myStrArr, 0);
32 Console.WriteLine("The string array contains:");
33 foreach (String s in myStrArr)
34 Console.WriteLine(" {0}", s);
35 Console.WriteLine();
36
37 // Searches for a key and deletes it.
38 myCol.Remove("green");
39 Console.WriteLine("The collection contains the following elements after removing \"green\":");
40 PrintKeysAndValues(myCol);
41
42 // Clears the entire collection.
43 myCol.Clear();
44 Console.WriteLine("The collection contains the following elements after it is cleared:");
45 PrintKeysAndValues(myCol);
46
47 }
48
49 public static void PrintKeysAndValues(NameValueCollection myCol)
50 {
51 Console.WriteLine(" KEY VALUE");
52 foreach (String s in myCol.AllKeys)
53 Console.WriteLine(" {0,-10} {1}", s, myCol[s]);
54 Console.WriteLine();
55 }
56
57 public static void PrintKeysAndValues2(NameValueCollection myCol)
58 {
59 Console.WriteLine(" [INDEX] KEY VALUE");
60 for (int i = 0; i < myCol.Count; i++)
61 Console.WriteLine(" [{0}] {1,-10} {2}", i, myCol.GetKey(i), myCol.Get(i));
62 Console.WriteLine();
63 }
64
65
66 }
67
68 /*
69
70 This code produces the following output.
71
72 Displays the elements using the AllKeys property and the Item (indexer) property:
73 KEY VALUE
74 red rojo,rouge
75 green verde
76 blue azul
77
78 Displays the elements using GetKey and Get:
79 [INDEX] KEY VALUE
80 [0] red rojo,rouge
81 [1] green verde
82 [2] blue azul
83
84 Index 1 contains the value verde.
85 Key "red" has the value rojo,rouge.
86
87 The string array contains:
88 rojo,rouge
89 verde
90 azul
91
92 The collection contains the following elements after removing "green":
93 KEY VALUE
94 red rojo,rouge
95 blue azul
96
97 The collection contains the following elements after it is cleared:
98 KEY VALUE
99
100
101 */reference: https://msdn.microsoft.com/zh-cn/library/system.collections.specialized.namevaluecollection.aspx