public class Account
{
    public string UserName { get; private set; }
    public string Password { get; private set; }

    public Account(string UserName, string Password)
    {
        // check to see if the userName or password contain a space. If so, it is an error as they
        // are not allowed to have spaces.
        if ( UserName.Contains(" ") || UserName.Contains(" ") ){
            throw new Exception("You are not allowed to have spaces in the user name or password.");
        }

        // You already passed the validation -- no need for the else statement since this will only be run
        // if no error is thrown :)
        this.UserName = UserName;
        this.Password = Password;
    }
}

// main method in some other class
public static Main(){
    try{
        Account account = new Account ("someUserName", "somePassword");

        // instead of writing it out to the console, you would just open the
        // filestream and shove it in there.
        Console.Writeln("my user name : " + account.UserName);
        Console.Writeln("my password  : " + account.Password);
    }
    catch(Exception e){
        Console.Writeln("An error occurred. The information is as follows : ");
        Console.Writeln("\tInnerException : " + e.InnerException);
        Console.Writeln("\tMessage : " + e.Message);
    }
}