ArrayList.CopyTo(Array，Int32)方法用于从目标数组的指定索引处开始，将整个ArrayList复制到兼容的一维Array。
句法：
public virtual void CopyTo (Array array, int arrayIndex);参数：
array: It is the one-dimensional Array that is the destination of the elements copied from ArrayList. The Array must have zero-based indexing.
arrayIndex: It is the zero-based index in array at which copying begins.
例外情况：
- ArgumentNullException：如果数组为null。
- ArgumentOutOfRangeException：如果arrayIndex小于零。
- 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(Array, Int32)
// 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");
// Creates and initializes the
// one-dimensional target Array.
String[] arr = new String[6];
// adding elements to Array
arr[0] = "HTML";
arr[1] = "PHP";
arr[2] = "Java";
arr[3] = "Python";
arr[4] = "C#";
arr[5] = "OS";
Console.WriteLine("Before Method: ");
Console.WriteLine("\nArrayList Contains: ");
// Displaying the elements in myList
for (int i = 0; i < myList.Count; i++) {
Console.WriteLine("myList[{0}] : {1}", i, myList[i]);
}
Console.WriteLine("\nArray Contains: ");
// Displaying the elements in arr
for (int i = 0; i < arr.Length; i++) {
Console.WriteLine("arr[{0}] : {1}", i, arr[i]);
}
Console.WriteLine("After Method: ");
// Copying the entire source ArrayList
// to the target Array starting at
// index 2.
myList.CopyTo(arr, 2);
Console.WriteLine("\nArrayList Contains: ");
// Displaying the elements in myList
for (int i = 0; i < myList.Count; i++) {
Console.WriteLine("myList[{0}] : {1}", i, myList[i]);
}
Console.WriteLine("\nArray Contains: ");
// Displaying the elements in arr
for (int i = 0; i < arr.Length; i++) {
Console.WriteLine("arr[{0}] : {1}", i, arr[i]);
}
}
}
输出：
Before Method:
ArrayList Contains:
myList[0] : A
myList[1] : B
myList[2] : C
myList[3] : D
Array Contains:
arr[0] : HTML
arr[1] : PHP
arr[2] : Java
arr[3] : Python
arr[4] : C#
arr[5] : OS
After Method:
ArrayList Contains:
myList[0] : A
myList[1] : B
myList[2] : C
myList[3] : D
Array Contains:
arr[0] : HTML
arr[1] : PHP
arr[2] : A
arr[3] : B
arr[4] : C
arr[5] : D
范例2：
// C# code to illustrate the
// ArrayList.CopyTo(Array, Int32)
// 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");
// 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 Method: ");
Console.WriteLine("\nArrayList Contains: ");
// Displaying the elements in myList
for (int i = 0; i < myList.Count; i++) {
Console.WriteLine("myList[{0}] : {1}", i, myList[i]);
}
Console.WriteLine("\nArray Contains: ");
// Displaying the elements in arr
for (int i = 0; i < arr.Length; i++) {
Console.WriteLine("arr[{0}] : {1}", i, arr[i]);
}
Console.WriteLine("After Method: ");
// using 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, 2);
Console.WriteLine("\nArrayList Contains: ");
// Displaying the elements in myList
for (int i = 0; i < myList.Count; i++) {
Console.WriteLine("myList[{0}] : {1}", i, myList[i]);
}
Console.WriteLine("\nArray Contains: ");
// Displaying the elements in arr
for (int i = 0; i < arr.Length; i++) {
Console.WriteLine("arr[{0}] : {1}", i, arr[i]);
}
}
}
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_System_Int32_