C＃中的索引构造函数

C＃8.0中Index Struct的Index(Int32，Boolean)构造函数用于初始化具有指定索引位置和值的新索引，该值显示索引是从集合或序列的开头还是结尾开始。如果指定的索引从头开始创建，则索引值1将指向最后一个元素，索引值0将指向最后一个元素之外。

句法：

public Index (int Value, bool FromEnd = false);

在这里，Value是索引值，并且是System.Int32类型。索引的值应等于或大于零。 FromEnd是一个布尔值，它指示索引是从集合或序列的开头还是结尾开始。在C＃8.0或更高版本上执行的以下代码：

范例1：

// C# program to illustrate
// the use of Index constructor
using System;
  
namespace example {
  
class GFG {
  
    static void Main(string[] args)
    {
        // Creating and initializing an array
        string[] greetings = new string[] {"Hello", "Hola", "Namaste", 
                                "Bonjour", "Ohayo", "Ahnyounghaseyo"};
  
        // Creating new indexes
        // Using Index() constructor
        var val1 = new Index(1, true);
        var val2 = new Index(2, true);
        var val3 = new Index(3, true);
        var val4 = new Index(1, false);
        var val5 = new Index(2, false);
        var val6 = new Index(3, false);
  
        // Getting the values of 
        // the specified indexes
        var res1 = greetings[val1];
        var res2 = greetings[val2];
        var res3 = greetings[val3];
        var res4 = greetings[val4];
        var res5 = greetings[val5];
        var res6 = greetings[val6];
  
        // Display indexes and their values
        Console.WriteLine("Index:{0} Value: {1}", val1, res1);
        Console.WriteLine("Index:{0} Value: {1}", val2, res2);
        Console.WriteLine("Index:{0} Value: {1}", val3, res3);
        Console.WriteLine("Index:{0} Value: {1}", val4, res4);
        Console.WriteLine("Index:{0} Value: {1}", val5, res5);
        Console.WriteLine("Index:{0} Value: {1}", val6, res6);
    }
}
}

输出：

Index:^1 Value: Ahnyounghaseyo
Index:^2 Value: Ohayo
Index:^3 Value: Bonjour
Index:1 Value: Hola
Index:2 Value: Namaste
Index:3 Value: Bonjour

范例2：

// C# program to illustrate 
// the use of Index constructor
using System;
  
namespace example {
  
class GFG {
  
    // Main Method
    static void Main(string[] args)
    {
  
        // Creating new indexes
        // Using Index() constructor
        var val1 = new Index(1, true);
        var val2 = new Index(2, true);
        var val3 = new Index(1, false);
        var val4 = new Index(2, false);
  
        // Checking if the specified 
        // index start from end or not
        var res1 = val1.IsFromEnd;
        var res2 = val2.IsFromEnd;
        var res3 = val3.IsFromEnd;
        var res4 = val4.IsFromEnd;
  
        // Display indexes and their values
        Console.WriteLine("Index:{0} Start from end?: {1}", val1, res1);
        Console.WriteLine("Index:{0} Start from end?: {1}", val2, res2);
        Console.WriteLine("Index:{0} Start from end?: {1}", val3, res3);
        Console.WriteLine("Index:{0} Start from end?: {1}", val4, res4);
    }
}
}

输出：

Index:^1 Start from end?: True
Index:^2 Start from end?: True
Index:1 Start from end?: False
Index:2 Start from end?: False