c#数的阶乘for while do-while

在 C# 中，计算一个数的阶乘可以使用 for、while 或 do-while 循环。以下是三种方法的示例：

1. **For循环**:

public long Factorial(int number)
{
    if (number < 0) throw new ArgumentException("Number must be non-negative.");
    long factorial = 1;
    for (int i = 1; i <= number; i++)
    {
        factorial *= i;
    }
    return factorial;
}

2. **While循环**:

public long FactorialWhile(int number)
{
    if (number < 0) throw new ArgumentException("Number must be non-negative.");
    int current = 1;
    long factorial = 1;
    while (current <= number)
    {
        factorial *= current;
        current++;
    }
    return factorial;
}

3. **Do-while循环**:

public long FactorialDoWhile(int number)
{
    if (number < 0) throw new ArgumentException("Number must be non-negative.");
    bool continueLoop = true;
    long factorial = 1;
    do
    {
        factorial *= current;
        current++;
    } while (continueLoop && current <= number);
    return factorial;
}

在上述代码中，`factorial`变量会保存计算出的阶乘结果。注意，对于大的数字，可能会超过 `long` 类型的最大值，这时需要考虑使用 `BigInteger` 类。