用c#定义描述复数的类，并实现复数的输入和输出。设计三个方法分别完成复数的加、减和乘法运算

在C#中，我们可以定义一个名为`ComplexNumber`的类来表示复数，包含实部（real）和虚部（imaginary）两个属性。下面是该类的基本定义以及用于输入输出和基本算术操作的方法：

using System;

public class ComplexNumber
{
    public double Real { get; set; }
    public double Imaginary { get; set; }

    // 构造函数，接收实部和虚部
    public ComplexNumber(double real, double imaginary)
    {
        Real = real;
        Imaginary = imaginary;
    }

    // 输入方法，从用户处获取复数
    public static ComplexNumber Input()
    {
        Console.Write("请输入实部: ");
        double real = double.Parse(Console.ReadLine());
        Console.Write("请输入虚部: ");
        double imaginary = double.Parse(Console.ReadLine());
        return new ComplexNumber(real, imaginary);
    }

    // 输出方法，打印复数
    public void Output()
    {
        Console.WriteLine($"复数 ({Real}, {Imaginary})");
    }

    // 加法运算方法
    public ComplexNumber Add(ComplexNumber other)
    {
        double realSum = Real + other.Real;
        double imaginarySum = Imaginary + other.Imaginary;
        return new ComplexNumber(realSum, imaginarySum);
    }

    // 减法运算方法
    public ComplexNumber Subtract(ComplexNumber other)
    {
        double realDifference = Real - other.Real;
        double imaginaryDifference = Imaginary - other.Imaginary;
        return new ComplexNumber(realDifference, imaginaryDifference);
    }

    // 乘法运算方法
    public ComplexNumber Multiply(ComplexNumber other)
    {
        double realProduct = Real * other.Real - Imaginary * other.Imaginary;
        double imaginaryProduct = Real * other.Imaginary + Imaginary * other.Real;
        return new ComplexNumber(realProduct, imaginaryProduct);
    }
}

你可以通过以下步骤使用这个类：

1. 创建复数实例并输入值
2. 执行相应的数学运算
3. 输出结果