Question

我想确保我的用户输入是6位数字并以数字1开头。我怎样才能确保输入以1开头？

private static void GetCustomerInfo(out string accNumberC)
    {
        string accNumberC;

    Console.Write("Account number: ");
        accNumberC = Console.ReadLine();

    if (accNumberC == "" || accNumberC.Length < 6 || accNumberC.Length > 6)
        {
            Console.WriteLine("Invalid data entered - no value redorded");
            accNumberC = null;
        }



    }

Answer 1

您可以像使用索引一样访问第一个字符：

if (accNumberC == "" || accNumberC.Length != 6 || accNumberC[0] != '1') //or use StartsWith
{
        Console.WriteLine("Invalid data entered - no value redorded");
        accNumberC = null;
}

Answer 2

if (string.IsNullOrEmpty(accNumberC) || accNumberC.Length != 6 || !accNumberC.StartsWith("1")) 
{
   Console.WriteLine("Invalid data entered - no value redorded");
}

Answer 3

只需使用accNumberC[0]=='1'比较并标记错误。

Answer 4

您可以尝试将输入的字符串解析为整数值：

int val;
if (!int.TryParse(accNumberC, out val))
{
    // string cannot be parsed as int.
    Console.WriteLine("Cannot parse entered value");
}
else if (val < 100000 || val > 199999)
{
    // value is not 6 digits length or doesn't start with 1.
    Console.WriteLine("Invalid data entered - no value redorded");
}
else
{
    // acceptable value here.
}

Answer 5

另一种解决方案是使用正则表达式。这是一个例子：

bool isValid(string accountNumber)
{
    if(String.IsNullOrWhiteSpace(accountNumber)) return false;

    var result = System.Text.RegularExpressions.Regex.Match(accountNumber,"^1\\d{5}$");
    return result.Success;
}

C＃输入验证，第一个数字必须是1？

5 个答案: