如何使用正则表达式判断邮箱(以C#为例)

//正则验证引用
using System.Text.RegularExpressions;

/// <summary>
///  验证QQ邮箱
/// </summary>
/// <param name="mail">邮箱</param>
/// <returns></returns>
public static bool CheckMail(string mail)
{
    string str = @"^[1-9][0-9]{4,}@qq.com$";
    Regex mReg = new Regex(str);

    if (mReg.IsMatch(mail))
    {
        return true;
    }
    return false;
}

^[1-9][0-9]{4,}@qq.com$

/// <summary>
/// 验证是否为邮箱
/// </summary>
/// <param name="mail"></param>
/// <returns></returns>
public static bool CheckAllMail(string mail)
{
    string str = @"^[a-zA-Z0-9_.-]+@[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*\.(com|cn|net)$";
    Regex mReg = new Regex(str);
 
    if (mReg.IsMatch(mail))
    {
        return true;
    }
    return false;
}

^[a-zA-Z0-9_.-]+@[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*\.(com|cn|net)$

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("请输入一个邮箱");
        string email = Console.ReadLine();
        Regex regex = new Regex(@"^(\w)+(\.\w)*@(\w)+((\.\w+)+)$");
        if (regex.IsMatch(email))
        {
            Console.WriteLine("邮箱格式正确。");
        }
        else
        {
            Console.WriteLine("邮箱格式不正确。");
        }
    }
}