使用 ref 和 out 传递数组
与所有的 out 参数一样,在使用数组类型的 out 参数前必须先为其赋值,即必须由接受方为其赋值。例如:
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![](/Images/OutliningIndicators/ExpandedBlockEnd.gif)
![](/Images/OutliningIndicators/None.gif)
与所有的 ref 参数一样,数组类型的 ref 参数必须由调用方明确赋值。因此不需要由接受方明确赋值。可以将数组类型的 ref 参数更改为调用的结果。例如,可以为数组赋以 null 值,或将其初始化为另一个数组。例如:
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![](/Images/OutliningIndicators/ExpandedBlockEnd.gif)
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下面的两个示例说明 out 和 ref 在将数组传递给方法上的用法差异。
示例 1
在此例中,在调用方(Main
方法)中声明数组 myArray
,并在 FillArray
方法中初始化此数组。然后将数组元素返回调用方并显示。
// cs_array_ref_and_out.cs
using System;
class TestOut
{
static public void FillArray(out int[] myArray)
{
// Initialize the array:
myArray = new int[5] {1, 2, 3, 4, 5};
}
static public void Main()
{
int[] myArray; // Initialization is not required
// Pass the array to the callee using out:
FillArray(out myArray);
// Display the array elements:
Console.WriteLine("Array elements are:");
for (int i=0; i < myArray.Length; i++)
Console.WriteLine(myArray[i]);
}
}
输出
![](/Images/OutliningIndicators/None.gif)
![](/Images/OutliningIndicators/None.gif)
![](/Images/OutliningIndicators/None.gif)
![](/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/InBlock.gif)
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
![](/Images/OutliningIndicators/ExpandedBlockEnd.gif)
![](/Images/OutliningIndicators/None.gif)
Array elements are: 1 2 3 4 5
示例 2
在此例中,在调用方(Main
方法)中初始化数组 myArray
,并通过使用 ref 参数将其传递给 FillArray
方法。在 FillArray
方法中更新某些数组元素。然后将数组元素返回调用方并显示。
// cs_array_ref_and_out2.cs using System; class TestRef { public static void FillArray(ref int[] arr) { // Create the array on demand: if (arr == null) arr = new int[10]; // Otherwise fill the array: arr[0] = 123; arr[4] = 1024; } static public void Main () { // Initialize the array: int[] myArray = {1,2,3,4,5}; // Pass the array using ref: FillArray(ref myArray); // Display the updated array: Console.WriteLine("Array elements are:"); for (int i = 0; i < myArray.Length; i++) Console.WriteLine(myArray[i]); } }
输出
Array elements are: 123 2 3 4 1024