从C＃中的较长字符串解析此数字的最佳方法是什么？

Question

I have the following example strings

"CTS3010 - 6ppl"

or

"CTs3200 - 14ppl"

or

 "CTS-500 2ppl"

and i need to parse out the number from these strings. What is the best way to parse out the number before the "ppl" at the end of the string. Do i need regex? I have logic to loop backward but it feels like there is a more elegant solution here.

These are just examples but all examples seem to follow the same pattern being

• A bunch of text
• A number
• ppl suffix

Answer 1

You can do this to grab the number right before "ppl":

using System.Text.RegularExpressions;
...

Regex regex = new Regex("([0-9]+)ppl");
string matchedValue = regex.Match("CTS-500 122ppl").Groups[1].Value;

In this case matchedValue will be 122.

If you want to be safe, and you know "ppl" will always be at the end of the string, I would change the Regex to: "([0-9]+)ppl$" (the only difference is the dollar sign at the end).

Answer 2

Here's one way using LINQ:

const String ppl = "ppl";
var examples = new[] { "CTS3010 - 6ppl", "CTs3200 - 14ppl", "CTS-500 2ppl" };
var delimiters = new[] { " " };
var result = examples
    .Select(e => e.Split(delimiters, StringSplitOptions.RemoveEmptyEntries))
    .Select(t => t.Last().ToLowerInvariant().Replace(ppl, String.Empty))
    .Select(Int32.Parse)
    .ToList();

Note that this will fail if it can't parse the integer value. If you can't guarantee each string will end with NNppl you'll need to check that it is a numeric value first.

Answer 3

I dunno about the "best way" but one method that is very easy to understand and modify is an extension method for a string object:

 public static int Parse(this string phrase)
    {
        if (string.IsNullOrWhiteSpace(phrase)) { throw new NullReferenceException("phrase is null");}

        string num = string.Empty;
        foreach (char c in phrase.Trim().ToCharArray()) {
            if (char.IsWhiteSpace(c)) { break; }
            if (char.IsDigit(c)) { num += c.ToString(); }
        }
        return int.Parse(num);
    }

Assumes " " is the break condition. You may prefer int.TryParse if there is some chance you don't get a number and/or maybe a System.Text.StringBuilder.