如何检查字符串中是否包含2个破折号？

Question

I am attempting to check that a string ( textBox1.Text ) has 2 dashes in it (eg XXXXX-XXXXX-XXXXX). I've had trouble figuring out the best way to do this without learning a whole new thing like Regex.

Right now I have:

else if (!textBox1.Text.Contains("-"))
{
    label3.Text = "Incorrect";
}

However, this only checks for 1 dash.

Basically, how would I have an if statement check if string textBox1.Text has exactly 2 dashes in it?

Answer 1

You can use the Count method

string input = "XXXXX-XXXXX-XXXXX";

var dashCounter = input.Count(x => x == '-');

then

if(dashCounter == 2) { }

Answer 2

Regex isn't really all that complicated, it's worth learning.

Here's a simple solution using LINQ.

int dashCount = textbox1.Text.Count(t=>t =='-');

Using TakeWhile as another suggested here will only show you the leading dashes . For example, to get 2 , you would need a string like --XX-XX (note that non-leading dashes wont be counted either).

Answer 3

You can check the count of dashes in a string with:

if str.Count(x => x == '-') != 2 { ... }

This basically means "count the number of items (characters) in the string when said item is equal to a dash". Checking it against two will allow you to detect the validity or otherwise of your input string.

---

If you were up to learning regular expressions, this is as good a place as any to start. You could check for a specific pattern with something like:

using System;
using System.Text.RegularExpressions;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string str = "XXXXX-XXXXX-XXXXX";
            Regex re = new Regex(@"^[^-]*-[^-]*-[^-]*$");
            Console.Out.WriteLine(re.Match(str).Success);
        }
    }
}

Now that regex may look complicated but it's relatively simple:

^       Start anchor.
[^-]*   Zero or more of any non-dash characters.
-       Dash character.
[^-]*   Zero or more of any non-dash characters.
-       Dash character.
[^-]*   Zero or more of any non-dash characters.
$       End anchor.