C#:study(3)--索引
＠索引
一唯索引的一般格式如下：
element-type this[int index]
{
get{...}//返回index指定的值
set{...}//为index指定的对象赋值
}
索引值通过index传递。索引是公共的，允许类以外的代码使用。索引不必即支持get又支持set。可以通过只实现get访问函数的方式来创建只读索引，也可以通过之实现set访问函数的方式来创建只写索引。使用索引有一条重要的限制：因为索引没有定义存储空间，用索引得到的值不能当作ref或out型参数传递给方法。
多维索引形式一般为：
public re-type this[int param1, ..., int paramN]
{
get
{
// process and return some class data
}
set
{
// process and assign some class data
}
}
注意：索引可以被重载，索引的参数可以任何类型。
结果为：
Indexer Output
myInd[0]: empty
myInd[1]: empty
myInd[2]: empty
myInd[3]: Another Value
myInd[4]: empty
myInd[5]: Any Value
myInd[6]: empty
myInd[7]: empty
myInd[8]: empty
myInd[9]: Some Value//一个重载的索引指示器
运行结果为：
Indexer Output
myInd[0]: no value
myInd[1]: no value
myInd[2]: no value
myInd[3]: Another Value
myInd[4]: no value
myInd[5]: Any Value
myInd[6]: no value
myInd[7]: no value
myInd[8]: no value
myInd[9]: Some Value
Number of "no value" entries: 7
一唯索引的一般格式如下：
element-type this[int index]
{
get{...}//返回index指定的值
set{...}//为index指定的对象赋值
}
索引值通过index传递。索引是公共的，允许类以外的代码使用。索引不必即支持get又支持set。可以通过只实现get访问函数的方式来创建只读索引，也可以通过之实现set访问函数的方式来创建只写索引。使用索引有一条重要的限制：因为索引没有定义存储空间，用索引得到的值不能当作ref或out型参数传递给方法。
多维索引形式一般为：
public re-type this[int param1, ..., int paramN]
{
get
{
// process and return some class data
}
set
{
// process and assign some class data
}
}
注意：索引可以被重载，索引的参数可以任何类型。
1using System;
2
///
3
/// A simple indexer example.
4
///
5class IntIndexer
6{
7private string[] myData;
8
9public IntIndexer(int size)
10
{
11myData = new string[size];
12for (int i=0; i < size; i++)
13{
14myData[i] = "empty";
15
}
16}
17public string this[int pos]
18{
19get
20{
21return myData[pos];
22}
23set
24{
25myData[pos] = value;
26}
27}
28
29static void Main(string[] args)
30{
31int size = 10;
32IntIndexer myInd = new IntIndexer(size);
33myInd[9] = "Some Value";
34myInd[3] = "Another Value";
35myInd[5] = "Any Value";
36Console.WriteLine("\nIndexer Output\n");
37for (int i=0; i < size; i++)
38{
39Console.WriteLine("myInd[{0}]: {1}", i, myInd[i]);
40}
41}
42}
using System;2
/// 
3
/// A simple indexer example.4
/// 5
class IntIndexer6
{
7
private string[] myData;8
9
public IntIndexer(int size)10
{
11
myData = new string[size];12
for (int i=0; i < size; i++)13
{14
myData[i] = "empty";15
}16
}17
public string this[int pos]18
{19
get20
{21
return myData[pos];22
}23
set24
{25
myData[pos] = value;26
}27
}28
29
static void Main(string[] args)30
{31
int size = 10;32
IntIndexer myInd = new IntIndexer(size);33
myInd[9] = "Some Value";34
myInd[3] = "Another Value";35
myInd[5] = "Any Value";36
Console.WriteLine("\nIndexer Output\n");37
for (int i=0; i < size; i++)38
{39
Console.WriteLine("myInd[{0}]: {1}", i, myInd[i]);40
}41
}42
}Indexer OutputmyInd[0]: emptymyInd[1]: emptymyInd[2]: emptymyInd[3]: Another ValuemyInd[4]: emptymyInd[5]: Any ValuemyInd[6]: emptymyInd[7]: emptymyInd[8]: emptymyInd[9]: Some Value 1using System;
2///
3/// Implements overloaded indexers.
4///
5class OvrIndexer
6{
7private string[] myData;
8private int arrSize;
9public OvrIndexer(int size)
10{
11arrSize = size;
12myData = new string[size];
13for (int i=0; i < size; i++)
14{
15myData[i] = "empty";
16}
17}
18
19public string this[int pos]
20{
21get
22{
23return myData[pos];
24}
25set
26{
27myData[pos] = value;
28}
29}
30
31public string this[string data]
32{
33get
34{
35int count = 0;
36for (int i=0; i < arrSize; i++)
37{
38if (myData[i] == data)
39{
40count++;
41}
42}
43return count.ToString();
44}
45set
46{
47for (int i=0; i < arrSize; i++)
48{
49if (myData[i] == data)
50{
51myData[i] = value;
52}
53}
54}
55}
56
57static void Main(string[] args)
58{
59int size = 10;
60OvrIndexer myInd = new OvrIndexer(size);
61myInd[9] = "Some Value";
62myInd[3] = "Another Value";
63myInd[5] = "Any Value";
64myInd["empty"] = "no value";
65Console.WriteLine("\nIndexer Output\n");
66for (int i=0; i < size; i++)
67{
68Console.WriteLine("myInd[{0}]: {1}", i, myInd[i]);
69}
70Console.WriteLine("\nNumber of \"no value\" entries: {0}", myInd["no value"]);
71}
72}
using System;2
/// 3
/// Implements overloaded indexers.4
/// 5
class OvrIndexer6
{7
private string[] myData;8
private int arrSize;9
public OvrIndexer(int size)10
{11
arrSize = size;12
myData = new string[size];13
for (int i=0; i < size; i++)14
{15
myData[i] = "empty";16
}17
}18
19
public string this[int pos]20
{21
get22
{23
return myData[pos];24
}25
set26
{27
myData[pos] = value;28
}29
}30
31
public string this[string data]32
{33
get34
{35
int count = 0;36
for (int i=0; i < arrSize; i++)37
{38
if (myData[i] == data)39
{40
count++;41
}42
}43
return count.ToString();44
}45
set46
{47
for (int i=0; i < arrSize; i++)48
{49
if (myData[i] == data)50
{51
myData[i] = value;52
}53
}54
}55
}56
57
static void Main(string[] args)58
{59
int size = 10;60
OvrIndexer myInd = new OvrIndexer(size);61
myInd[9] = "Some Value";62
myInd[3] = "Another Value";63
myInd[5] = "Any Value";64
myInd["empty"] = "no value";65
Console.WriteLine("\nIndexer Output\n");66
for (int i=0; i < size; i++)67
{68
Console.WriteLine("myInd[{0}]: {1}", i, myInd[i]);69
}70
Console.WriteLine("\nNumber of \"no value\" entries: {0}", myInd["no value"]);71
}72
}Indexer OutputmyInd[0]: no valuemyInd[1]: no valuemyInd[2]: no valuemyInd[3]: Another ValuemyInd[4]: no valuemyInd[5]: Any ValuemyInd[6]: no valuemyInd[7]: no valuemyInd[8]: no valuemyInd[9]: Some ValueNumber of "no value" entries: 7
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