如何在C＃中从一个分隔符提取子字符串到另一个分隔符？

Question

My input is going to be as follows: abc@gmail.com,def@yahoo.com;xyz@gmail.com;ghi@hotmail.com and so on

Now I want my output to be: abc def xyz ghi

The following is my code:

using System;
using System.Text.RegularExpressions;

public class Program
{
    public static void Main(string[] args)
    {
        string str;
        string[] newstr,newstr2;
        Console.WriteLine("Enter the email addresses: ");
        str=Console.ReadLine();
        newstr=Regex.Split(str,",|;|@");
        foreach (string s in newstr)
        {
            Console.WriteLine(s);
        }
    }
}

My output right now is: abc gmail.com def yahoo.com xyz gmail.com ghi hotmail.com

Any kind of help would be greatly appreciated. Thanks.

Answer 1

You shouldn't use regex for split, and should no split by @ . Instead, use the follopwing code:

using System;

public class Program
{
    public static void Main(string[] args)
    {
        string str;
        string[] newstr;
        Console.WriteLine("Enter the email addresses: ");
        str = Console.ReadLine();
        newstr = str.Split(new char[] { ',', ';' }); // Split to get a temporal array of addresses 
        foreach (string s in newstr)
        {
            Console.WriteLine(s.Substring(0, s.IndexOf('@'))); // Extract the sender from the email addresses
        }
    }
}

Edit:

Or, with LINQ:

using System;
using System.Linq;

public class Program
{
    public static void Main(string[] args)
    {
        string str;
        string[] newstr;
        Console.WriteLine("Enter the email addresses: ");
        str = Console.ReadLine();
        newstr = str.Split(new char[] { ',', ';' })  // Split to get a array of addresses to work with
            .Select(s => s.Substring(0, s.IndexOf('@'))).ToArray(); // Extract the sender from the email addresses
        foreach (string s in newstr)
        {
            Console.WriteLine(s);
        }
    }
}

Answer 2

another approach without RegEx

string input = "abc@gmail.com,def@yahoo.com;xy@gmail.com; ghi@hotmail.com";
var result = input.Split(',', ';').Select(x => x.Split('@').First());

first Split the adresses by , and ; , then select the part before the @ by splitting again.

Answer 3

You can use this email regex:

            var regex = new Regex(@"(?<name>\w+([-+.']\w+)*)@\w+([-.]\w+)*\.\w+([-.]\w+)*");

            var results =
            regex.Matches("abc@gmail.com,def@yahoo.com;xyz@gmail.com;ghi@hotmail.com")
                .Cast<Match>()
                .Select(m => m.Groups["name"].Value)
                .ToList();

Answer 4

也许使用它可能有所帮助

str.Substring(0, str.LastIndexOf(" ")<0?0:str.LastIndexOf(" "));

Answer 5

As Mail is a weird thing with a complexe definition, I will never assume that something with an @ is a mail.
My best try would be to convert the string to a MailAddress, just in case it look like a mail but it's not one because of some invalid char etc.

string input = "abc@gmail.com,ghi@hotmail.com;notme; @op this is not a mail!";
var result = input
                .Split(',', ';')    // Split
                .Select(x =>
                {
                    string adr = "";
                    try
                    {   // Create an MailAddress, MailAddress has no TryParse.
                        adr = new MailAddress(x).User;
                    }
                    catch
                    {
                        return new { isValid = false, mail = adr };
                    }
                    return new { isValid = true, mail = adr };
                })
                .Where(x => x.isValid)
                .Select(x => x.mail);

Answer 6

Actually, in the regular expression, to capture some substring, you need to wrap the expected content by ( and )

Below code should work

string str22 = "abc@gmail.com;def@yahoo.com,xyz@gmail.com;fah@yao.com,h347.2162@yahoo.com.hk";// ghi@hotmail.com";
List<string> ret = new List<string>();
string regExp = @"(.*?)@.*?[,;]{1}|(.*)@";
MatchCollection matches = Regex.Matches(str22, regExp, RegexOptions.IgnoreCase);
foreach (Match match in matches)
{
    if (match.Success)
    {
        int pvt = 1;
        while (string.IsNullOrEmpty(match.Groups[pvt].Value))
        {
            pvt++;
        }
        MessageBox.Show(match.Groups[pvt].Value);
    }
}
return;

The regular expression is as below

  (.*?)@.*?[,;]{1}|(.*)@

(.*?)@.*?[,;]{1} is fetching the substring before @ and ? restrict it fetches the first match.

The last email do not contain , or ; , thus add a OR condition and fetch the last email name by the substring before @