params(C# 参考)params (C# Reference)

使用 params 关键字可以指定采用数目可变的参数的方法参数By using the params keyword, you can specify a method parameter that takes a variable number of arguments. 参数类型必须是一维数组。The parameter type must be a single-dimensional array.

在方法声明中的 params 关键字之后不允许有任何其他参数,并且在方法声明中只允许有一个 params 关键字。No additional parameters are permitted after the params keyword in a method declaration, and only one params keyword is permitted in a method declaration.

如果 params 参数的声明类型不是一维数组,则会发生编译器错误 CS0225If the declared type of the params parameter is not a single-dimensional array, compiler error CS0225 occurs.

使用 params 参数调用方法时,可以传入:When you call a method with a params parameter, you can pass in:

  • 数组元素类型的参数的逗号分隔列表。A comma-separated list of arguments of the type of the array elements.
  • 指定类型的参数的数组。An array of arguments of the specified type.
  • 无参数。No arguments. 如果未发送任何参数,则 params 列表的长度为零。If you send no arguments, the length of the params list is zero.

示例Example

下面的示例演示可向 params 形参发送实参的各种方法。The following example demonstrates various ways in which arguments can be sent to a params parameter.

public class MyClass
{
    public static void UseParams(params int[] list)
    {
        for (int i = 0; i < list.Length; i++)
        {
            Console.Write(list[i] + " ");
        }
        Console.WriteLine();
    }

    public static void UseParams2(params object[] list)
    {
        for (int i = 0; i < list.Length; i++)
        {
            Console.Write(list[i] + " ");
        }
        Console.WriteLine();
    }

    static void Main()
    {
        // You can send a comma-separated list of arguments of the
        // specified type.
        UseParams(1, 2, 3, 4);
        UseParams2(1, 'a', "test");

        // A params parameter accepts zero or more arguments.
        // The following calling statement displays only a blank line.
        UseParams2();

        // An array argument can be passed, as long as the array
        // type matches the parameter type of the method being called.
        int[] myIntArray = { 5, 6, 7, 8, 9 };
        UseParams(myIntArray);

        object[] myObjArray = { 2, 'b', "test", "again" };
        UseParams2(myObjArray);

        // The following call causes a compiler error because the object
        // array cannot be converted into an integer array.
        //UseParams(myObjArray);

        // The following call does not cause an error, but the entire
        // integer array becomes the first element of the params array.
        UseParams2(myIntArray);
    }
}
/*
Output:
    1 2 3 4
    1 a test

    5 6 7 8 9
    2 b test again
    System.Int32[]
*/

C# 语言规范C# language specification

有关详细信息,请参阅 C# 语言规范For more information, see the C# Language Specification. 该语言规范是 C# 语法和用法的权威资料。The language specification is the definitive source for C# syntax and usage.

请参阅See also