如何检查邮政编码是否在C＃文本框中正确输入

Question

For my school I need to make a program that checks if you give in the right postal code: for example it need to be in this format: 0000 XX. It's a dutch postal code.

I'm trying to find out how to do this, but I really don't know how to fix this problem. i can't use Regex, because we havent learnt that yet.

The events that I'm allowed to use:

TextChanged
KeyDown
KeyPress
KeyUp

Functions that i'm allowed to use:

char.isNumber();
char.isLetter();

If anyone could help me, that would be awesome. Thanks in advance.

Answer 1

As a help for a homework:

In the OnTextChanged-event iterate through the String:

if string is longer than 7?: fail

for each character in string:
  if char-pos <= 4 && character is not number: fail
  if char-pos == 5 && character is not whitespace: fail
  if char-pos > 5 && character is not letter: fail
end

good luck.

Answer 2

With respect, you CAN use RegEx - because RegEx is the proper solution that we would all use. Don't be afraid to move forward from your course and learn things on your own as well...

However, sticking to the functions you highlight...

using System;

namespace SO5
{
    class Program
    {
        public static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");

            Console.WriteLine(TestPostcode("1234 XC"));
            Console.WriteLine(TestPostcode("D4 XC"));
            Console.WriteLine(TestPostcode("4632 XC1"));

            Console.Write("Press any key to continue . . . ");
            Console.ReadKey(true);
        }

        public static bool TestPostcode(string input)
        {
            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            foreach (char c in input)
            {
                if (char.IsLetter(c))
                {
                    sb.Append("L");
                }
                else if (char.IsNumber(c))
                {
                    sb.Append("N");
                }
            }

            return sb.ToString() == "NNNNLL";

        }

    }
}

Now, if you want to impress, read about something called Unit Testing and a (free) product called NUnit. You will then be able to both execute your method with test cases at will, whilst also having effective tests that the thing still works...

Answer 3

A few ways you can go about it, but i'll give you a hint to how I would do it.

Handle TextChanged, and in that method get the string for the text entered.

Loop through each character, and depending on the position, check for the type of character you are looking for.