基本的C#数字运算示例，执行两个数的加法、减法运算，返回相加、相减后的结果，实例化类对象，定义一个死循环，以便循环输入数据，记录运算符号，以运算符号为条件进行判断，判断是否为加号，判断是否为减号，不符合上面所有情况，实现基本的加法、减法运算。-The basic number crunching C# example, perform the addition of two numbers, subtraction, back together, after subtracting the result of instantiating the class object that defines an infinite loop to loop the input data, records arithmetic symbols to arithmetic symbols conditions to judge, to determine whether the plus sign to determine whether the minus sign, does not meet all of the above cases, the basic addition and subtraction.