C#正則表達式基礎入門訓練_艾孜爾江撰

namespace ： System.Text.RegularExpressions.

static void Main(string[] args)
{
    // if (IsInputMatchesNumber())
    if (IsInputMatchesNumberByRegx())
    {
        Console.WriteLine("Input charectors are all numbers.");
    }
    else
    {
        Console.WriteLine("Input charectors are not pure numbers.");
    }
}

//Common way to judge whether a string is pure numbers or not
static bool IsInputMatchesNumber()
{
    Console.Write("Please input your password: ");
    string str = Console.ReadLine();
    bool isMatch = true;
    for (int i = 0; i < str.Length; i++)
    {
        if (str[i] < '0' || str[i] > '9')
        {
            isMatch = false;
            break;
        }
    }
    return isMatch;
}


//Use regular expressions to judge, result is the same as above 
static bool IsInputMatchesNumberByRegx()
{
    Console.Write("Please input your password: ");
    string str = Console.ReadLine();
    //Regular expression always come with @
    // @  means "do not convert \ in string"
    // ^  means "start from"
    // $  means "end at"
    // *  means "has any"
    // \d means "number"
    string pattern = @"^\d*$";
    return Regex.IsMatch(str, pattern);
}