c# - C#烦恼-在sting之外访问数据

我已经用C＃编写了一个电子邮件验证程序，但是如何检查字符串之外的数据？

这是我的C＃代码：

private bool CheckEmail()
{
    string email1 = email.Text;

    //calculating the length of the email
    int EmailLen = email1.Length;
    int num = 0;

    //the first character of the email must not be the "@"
    if (email1.Substring(0, 1) != "@")
    {
        //checking the email entered after the first character as it is not a "@" so i will start from 1.
        for (int i = 1; i < EmailLen; i++)
        {
            //prevents there from being two "@"next to each other
            if (email1[i] == '@' && (i + 1) < email1.Length && email1[i + 1] != '@')
            {
                //if there is an "@" in the email then num will increase by one
                num = num + 1;

                //now the stored value of i is the position where the "@" is placed. j will be i+2 as there should be at least one character after the "@"
                int j = i + 2;
                if (j < EmailLen)
                {
                    for (int k = j; k < EmailLen; k++)
                    {
                        //when it finds a "." In the email, the character after the "." Should not be empty or have a space, e.g. it should be something like ".com"

                        if (email1[k] == '.' && k + 1 < email1.Length && email1[k + 1] != ' ')
                        {
                            num = num + 1;
                        }
                    }
                }
                else
                {
                    break;
                }
            }
        }
    }
    else
    {
        num = 0;
    }

    //if the num is 2, then the email is valid, otherwise it is invalid.  If the email had more than one "@" for example, the num will be greater than 2.

    if (num == 2)
    {
        return true;
    }
    else
    {
        return false;
    }
}

当我尝试输入“ aa @”时，出现以下错误：“索引和长度必须引用字符串中的位置。”



当我输入aa @ a时。 ，出现此错误：“索引和长度必须引用字符串中的位置。”

最佳答案

您不能访问字符串之外的数据。这是有很好的理由-这样做会违反类型安全性，而后者是.NET CLR这样的虚拟机的主要吸引力。

您只想检查边界以确保您不尝试访问不存在的字符串部分。顺便说一句，对于检查单个字符，您完全想执行email1[i]而不是email1.Substring(i, 1)，因此您不必在左侧，右侧和中间构造新的字符串对象。

您的第一个测试应该是：

if (email1[i] == '@' && i + 1 < email1.Length && email1[i + 1] != '@')

关于c# - C#烦恼-在sting之外访问数据，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/15624424/