如果C#中的用户输入为空，则重复该问题

Question

我的学校代码有一个基本问题。代码需要作为控制台程序询问用户输入，但在继续操作之前，我需要它在输入空字段时重复这个问题。到目前为止，我已经尝试了很多while循环！isStringNullorEmpty，stringlength，试图创建一个函数来检查它和一些if语句。这两件事我都做不了。程序一直进行到最后。

System.Console.Write("Give first name");
String firstname = System.Console.ReadLine();
System.Console.Write("Give last name");
String lastname = System.Console.ReadLine();
System.Console.Write("Give date of birth");
DateTime = dt = DateTime.Parse(System.Console.ReadLine();

Answer 1

您可以尝试

string firstName = null;
Console.WriteLine("Give first name");
while(string.IsNullOrWhiteSpace(firstName = Console.ReadLine()))
  Console.WriteLine("OMG you had one job as a user of this application, to put in the right value!");

您可以对DateTime 执行相同操作

Console.Write("Give date of birth");
while (!DateTime.TryParse(Console.ReadLine(),out var dob))
    Console.Write("OMG you had one job as a user of this application, to put in the right value!");

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其他资源

DateTime.TryParse方法

将指定的日期和时间的字符串表示形式转换为其DateTime等效，并返回一个值，该值指示转换成功。

Answer 2

您可以编写

   System.Console.Write("Give first name");
   String firstname = null;
   while(firstname==null || firstname==""){
       firstname = System.Console.ReadLine();
   }

Answer 3

试试这个：

String lastname = null;
Console.Write("Give last name: ");
while (!String.IsNullOrEmpty(lastname)) {
    lastname = System.Console.ReadLine();
}

Answer 4

试试这个

            var firstname = string.Empty;
            var lastname = string.Empty;
            var dt = DateTime.MinValue;
            do
            {
                System.Console.Write("Give first name");
                 firstname = System.Console.ReadLine();
            } while (string.IsNullOrEmpty(firstname));
            do
            {
                System.Console.Write("Give last name");
                 lastname = System.Console.ReadLine();
            } while (string.IsNullOrEmpty(lastname));

            do
            {
                System.Console.Write("Give date of birth");
                 dt = DateTime.Parse(System.Console.ReadLine());
            } while (dt != DateTime.MinValue);

Answer 5

尝试这个

        bool value = true;
        while (value==true)
        {
            System.Console.Write("Give first name");
            String firstname = System.Console.ReadLine();
            if (firstname == "")
            {
                value = false;
                break;
            }
            System.Console.Write("Give last name");
            String lastname = System.Console.ReadLine();
            if (lastname == "")
            {
                value = false;
                break;
            }
            System.Console.Write("Give date of birth");
             DateTime dt = DateTime.Parse(System.Console.ReadLine());
            if (dt.ToString()=="")
            {
                value = false;
                break;
            }
        }