ArrayList.CopyTo方法用于从目标数组的开头开始，将整个ArrayList复制到兼容的一维Array。
句法：
public virtual void CopyTo (Array array);在这里， 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：如果数组为null。
- ArgumentException：如果数组是多维数组，或者源ArrayList中的元素数大于目标数组可以包含的元素数。
- InvalidCastException：如果无法将源ArrayList的类型强制转换为目标array的类型。
下面的程序说明了上面讨论的方法的使用：
范例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：
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
范例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：
Unhandled Exception:
System.ArgumentException: Destination array was not long enough. Check destIndex and length, and the array’s lower bounds
Parameter name: 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_