如何限制字符串中可以包含的字符数？

Question

I'm writing a program that limits how many characters can be in the output. Essentially a student id assigner and I'm now sure how to count only a specific amount of characters in a string. My code looks like this so far.

 string firstname, middleinitial, lastname,yearofentry;
        int year;
        Console.WriteLine("Please enter your first name.");
        firstname = Console.ReadLine();

        Console.WriteLine("Please enter your middle initial.");
        middleinitial = Console.ReadLine();

        Console.WriteLine("Please enter your last name.");
        lastname = Console.ReadLine();

        Console.WriteLine("Please enter your year of entry.");
        yearofentry = Console.ReadLine();
        year = (Convert.ToInt32(yearofentry)-2000);



        Console.WriteLine(firstname +middleinitial+ lastname + year + "@mail.edu");
    }
}

}

Answer 1

Just read in the full string, TrimStart() it and then use Substring() to get the parts you need

Console.WriteLine("Please enter your last name.");
lastname = Console.ReadLine().TrimStart();
var substrLen = Math.Min(lastname.Length, 7);
lastname = lastname.Substring(0, substrLen);

In the last WriteLine() call you can use .ToString("00") to get the 2 digits you require

Console.WriteLine(firstname + middleinitial + lastname + year.ToString("00") + "@mail.edu");

You should check that your users are entering a value between 2000 and 2099 though also.