c#判断email地址是否为合法

class Program{static void Main(string[] args){Console.WriteLine("请输入正确的邮箱地址，以 @sina.com 结尾");string us =Convert.ToString(Console.ReadLine());string str1 = us.Replace("@", "");int count = us.Length - str1.Length;string str2 = us.Replace(".", "");int count2 = us.Length - str2.Length;int count3 = us.Length - 1;int xl=us.IndexOf(".")-us.IndexOf("@");bool mw = (us.IndexOf("@sina.com") == (us.Length-9));while (count == 1 && count2 == 1 && us.IndexOf("@") > 0 && us.IndexOf(".") > us.IndexOf("@") && us.IndexOf(".")<count3){if (xl != 1 && us.Contains("@sina.com") && mw){Console.WriteLine("正确");}else {Console.WriteLine("输入的邮箱地址有误");}break;}Console.ReadLine();}}