傳遞陣列當做引數 (C# 程式設計手冊)

發行項
06/10/2015

您可以將陣列當做引數傳遞至方法參數。由於陣列是參考型別，因此方法可變更元素的值。

將一維陣列當做引數傳遞

您可以將初始化的一維陣列傳遞至方法。例如，下列陳述式會傳送陣列至列印方法。

int[] theArray = { 1, 3, 5, 7, 9 };
PrintArray(theArray);

下列程式碼顯示列印方法的部分實作。

void PrintArray(int[] arr)
{
    // Method code.
}

您可以在一個步驟中初始化並傳遞新陣列，如下列範例所示。

PrintArray(new int[] { 1, 3, 5, 7, 9 });

範例

描述

在下列範例中，會初始化字串陣列，並將其當做引數傳遞至 PrintArray 方法做為字串。方法會顯示陣列的元素。接著會呼叫 ChangeArray 和 ChangeArrayElement 方法，示範透過值傳送陣列引數無法避免改變陣列元素。

程式碼

class ArrayClass
{
    static void PrintArray(string[] arr)
    {
        for (int i = 0; i < arr.Length; i++)
        {
            System.Console.Write(arr[i] + "{0}", i < arr.Length - 1 ? " " : "");
        }
        System.Console.WriteLine();
    }

    static void ChangeArray(string[] arr)
    {
        // The following attempt to reverse the array does not persist when 
        // the method returns, because arr is a value parameter.
        arr = (arr.Reverse()).ToArray();
        // The following statement displays Sat as the first element in the array.
        System.Console.WriteLine("arr[0] is {0} in ChangeArray.", arr[0]);
    }

    static void ChangeArrayElements(string[] arr)
    {
        // The following assignments change the value of individual array  
        // elements. 
        arr[0] = "Sat";
        arr[1] = "Fri";
        arr[2] = "Thu";
        // The following statement again displays Sat as the first element 
        // in the array arr, inside the called method.
        System.Console.WriteLine("arr[0] is {0} in ChangeArrayElements.", arr[0]);
    }

    static void Main()
    {
        // Declare and initialize an array. 
        string[] weekDays = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };

        // Pass the array as an argument to PrintArray.
        PrintArray(weekDays);

        // ChangeArray tries to change the array by assigning something new 
        // to the array in the method. 
        ChangeArray(weekDays);

        // Print the array again, to verify that it has not been changed.
        System.Console.WriteLine("Array weekDays after the call to ChangeArray:");
        PrintArray(weekDays);
        System.Console.WriteLine();

        // ChangeArrayElements assigns new values to individual array 
        // elements.
        ChangeArrayElements(weekDays);

        // The changes to individual elements persist after the method returns. 
        // Print the array, to verify that it has been changed.
        System.Console.WriteLine("Array weekDays after the call to ChangeArrayElements:");
        PrintArray(weekDays);
    }
}
// Output:  
// Sun Mon Tue Wed Thu Fri Sat 
// arr[0] is Sat in ChangeArray. 
// Array weekDays after the call to ChangeArray: 
// Sun Mon Tue Wed Thu Fri Sat 
//  
// arr[0] is Sat in ChangeArrayElements. 
// Array weekDays after the call to ChangeArrayElements: 
// Sat Fri Thu Wed Thu Fri Sat

將多維陣列當做引數傳遞

傳遞已初始化多維陣列至方法的方式，和傳遞一維陣列相同。

int[,] theArray = { { 1, 2 }, { 2, 3 }, { 3, 4 } };
Print2DArray(theArray);

下列程式碼顯示列印方法的部分宣告，此方法接受二維陣列做為其引數。

void Print2DArray(int[,] arr)
{
    // Method code.
}

您可以在一個步驟中初始化並傳遞新陣列，如下列範例所示。

Print2DArray(new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } });

範例

描述

在下列範例中，會初始化整數的二維陣列，並將其傳遞至 Print2DArray 方法。方法會顯示陣列的元素。

程式碼

class ArrayClass2D
{
    static void Print2DArray(int[,] arr)
    {
        // Display the array elements. 
        for (int i = 0; i < arr.GetLength(0); i++)
        {
            for (int j = 0; j < arr.GetLength(1); j++)
            {
                System.Console.WriteLine("Element({0},{1})={2}", i, j, arr[i, j]);
            }
        }
    }
    static void Main()
    {
        // Pass the array as an argument.
        Print2DArray(new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } });

        // Keep the console window open in debug mode.
        System.Console.WriteLine("Press any key to exit.");
        System.Console.ReadKey();
    }
}
    /* Output:
        Element(0,0)=1
        Element(0,1)=2
        Element(1,0)=3
        Element(1,1)=4
        Element(2,0)=5
        Element(2,1)=6
        Element(3,0)=7
        Element(3,1)=8
    */