C#如何将整个ArrayList复制到一维数组

ArrayList.CopyTo方法用于复制整个数组列表到兼容的一维数组, 从目标数组的开头开始。

语法如下：

public virtual void CopyTo (Array array);

这里, Array是一维Array, 它是从ArrayList复制的元素的目的地。数组必须具有从零开始的索引。

例外情况：

• ArgumentNullException：如果Array一片空白。
• ArgumentException：如果Array是多维的OR源ArrayList中的元素数大于目标ArrayList中的元素数Array可以包含。
• InvalidCastException：如果源ArrayList的类型不能自动转换为目标的类型Array.

下面的程序说明了上述方法的使用：

示例1：

//C# code to illustrate the
//ArrayList.CopyTo Method
using System;
using System.Collections;
  
class GFG {
  
     //Driver code
     public static void Main()
     {
  
         //Creating an ArrayList
         ArrayList myList = new ArrayList();
  
         //Adding elements to ArrayList
         myList.Add( "A" );
         myList.Add( "B" );
         myList.Add( "C" );
         myList.Add( "D" );
         myList.Add( "E" );
         myList.Add( "F" );
         myList.Add( "G" );
         myList.Add( "H" );
  
         //Creates and initializes the
         //one-dimensional target Array.
         String[] arr = new String[9];
  
         arr[0] = "C" ;
         arr[1] = "C++" ;
         arr[2] = "Java" ;
         arr[3] = "Python" ;
         arr[4] = "C#" ;
         arr[5] = "HTML" ;
         arr[6] = "CSS" ;
         arr[7] = "PHP" ;
         arr[8] = "DBMS" ;
  
         Console.WriteLine( "Before CopyTo Method: " );
  
         Console.WriteLine( "\nArrayList Contains: " );
  
         //printing ArrayList elements
         foreach (Object obj in myList)
             Console.WriteLine( "{0}" , obj);
  
         Console.WriteLine( "\nString Array Contains: " );
  
         //printing String elements
         foreach (Object obj1 in arr)
             Console.WriteLine( "{0}" , obj1);
  
         Console.WriteLine( "After CopyTo Method: " );
  
         //using CopyTo Method to copy
         //the entire source ArrayList
         //to the target Array starting
         //at index 0
         myList.CopyTo(arr);
  
         Console.WriteLine( "\nArrayList Contains: " );
  
         //printing ArrayList elements
         foreach (Object obj in myList)
             Console.WriteLine( "{0}" , obj);
  
         Console.WriteLine( "\nString Array Contains: " );
  
         //printing String elements
         foreach (Object obj1 in arr)
             Console.WriteLine( "{0}" , obj1);
     }
}

输出如下：

Before CopyTo Method: 

ArrayList Contains: 
A
B
C
D
E
F
G
H

String Array Contains: 
C
C++
Java
Python
C#
HTML
CSS
PHP
DBMS

After CopyTo Method: 

ArrayList Contains: 
A
B
C
D
E
F
G
H

String Array Contains: 
A
B
C
D
E
F
G
H
DBMS

示例2：

//C# code to illustrate the
//ArrayList.CopyTo Method
using System;
using System.Collections;
  
class GFG {
  
     //Driver code
     public static void Main()
     {
  
         //Creating an ArrayList
         ArrayList myList = new ArrayList();
  
         //Adding elements to ArrayList
         myList.Add( "HTML" );
         myList.Add( "CSS" );
         myList.Add( "PHP" );
         myList.Add( "DBMS" );
  
         //Creates and initializes the
         //one-dimensional target Array.
         //Here array size is only 2 i.e
         //it can hold only 3 elements.
         String[] arr = new String[2];
  
         Console.WriteLine( "Before CopyTo Method: " );
  
         Console.WriteLine( "\nArrayList Contains: " );
  
         //printing ArrayList elements
         foreach (Object obj in myList)
             Console.WriteLine( "{0}" , obj);
  
         Console.WriteLine( "\nString Array Contains: " );
  
         //printing String elements
         foreach (Object obj1 in arr)
             Console.WriteLine( "{0}" , obj1);
  
         Console.WriteLine( "After CopyTo Method: " );
  
         //using CopyTo Method but It will give
         //Runtime Error as number of elements
         //in the source ArrayList is greater
         //than the number of elements that
         //the destination array can contain
         myList.CopyTo(arr);
  
         Console.WriteLine( "\nArrayList Contains: " );
  
         //printing ArrayList elements
         foreach (Object obj in myList)
             Console.WriteLine( "{0}" , obj);
  
         Console.WriteLine( "\nString Array Contains: " );
  
         //printing String elements
         foreach (Object obj1 in arr)
             Console.WriteLine( "{0}" , obj1);
     }
}

运行时错误：

未处理的异常：System.ArgumentException：目标数组不够长。检查destIndex和length, 以及数组的下限参数名称：destinationArray

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.collections.arraylist.copyto?view=netframework-4.7.2#System_Collections_ArrayList_CopyTo_System_Array_

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