CODEWITHSUNDEEP
c#regex
Alan
Alan

Reputation: 33

how to get a part from a string with regular expression in C#

How do I get 'Name' value and 'Age' value?

Case1 Data:

aaa bbbb; Name=John Lewis; ccc ddd; Age=20;

Case2 Data:

AAA bbbb; Age=21;

My regular expression:

(?:Name=(?'name'[\w\b]+)\;)[\s\S]*Age=(?'age'\d+)\;?

But no way to get values(Name, Age).

Upvotes: 1

Views: 205

Answers (4)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626747

Case 1: Only Name is optional

A regex for your case should account for an optional Name field.

(?:\bName=(?<Name>[^;]+).*?;\s+)?\bAge=(?<Age>\d+)
^^^                            ^^

See the regex demo

If Name and Age data are on separate lines, use the regex with RegexOptions.Singleline flag.

Details:

  • (?:\bName=(?<Name>[^;]+).*?;\s+)? - an optional string of subpatterns
    • \bName= - a whole word "Name" + =
    • (?<Name>[^;]+) - Group "Name" capturing 1+ chars other than ;
    • .*? - any 0+ chars (other than newline if (?s) is not used)
    • ; - a semi-colon
    • \s+ - 1 or more whitespaces
  • \bAge= - whole word Age + =
  • (?<Age>\d+) - Capturing group "Age" matching 1+ digits.

C# demo:

var strs = new[] { "aaa bbbb; Name=John Lewis; ccc ddd; Age=20;", "AAA bbbb; Age=21;" };
var pattern = @"(?:\bName=(?<Name>[^;]+).*?;\s+)?\bAge=(?<Age>\d+)";
foreach (var str in strs) 
{
    var result = Regex.Match(str, pattern);
    if (result.Success) 
        Console.WriteLine("Name: \"{0}\", Age: \"{1}\"", result.Groups["Name"].Value, result.Groups["Age"].Value);
}
// => Name: "John Lewis", Age: "20"
//    Name: "", Age: "21"

Case 2: Both Name and Age are optional

Use optional groups for both fields:

(?:\bName=(?<Name>[^;]+).*?;\s+)?(?:\bAge=(?<Age>\d+))?
^^^                            ^^^^^                 ^^

See this C# demo

var strs = new[] { "aaa bbbb; Name=John Lewis; ccc ddd; Age=20;", "AAA bbbb; Age=21;", "Irrelevant", "My Name=Wiktor; no more data" };
var pattern = @"(?:\bName=(?<Name>[^;]+).*?;\s+)?(?:\bAge=(?<Age>\d+))?";
foreach (var str in strs) 
{
    var results = Regex.Matches(str, pattern)
        .Cast<Match>()
        .Where(m => m.Groups["Name"].Success || m.Groups["Age"].Success)
        .Select(p => new {key=p.Groups["Name"].Value, val=p.Groups["Age"].Value} )
        .ToList();
    foreach (var r in results)
        Console.WriteLine("Name: \"{0}\", Age: \"{1}\"", r.key, r.val);
}

Else, if you want to use a more regex engine-friendly pattern, use an alternation with 2 branches where either of the two patterns are obligatory (so as to avoid empty matches handling):

var strs = new[] { "aaa bbbb; Name=John Lewis; ccc ddd; Age=20;", "AAA bbbb; Age=21;", "Irrelevant", "My Name=Wiktor; no more data" };
var pattern = @"(?:\bName=(?<Name>[^;]+).*?;\s+)?\bAge=(?<Age>\d+)|\bName=(?<Name>[^;]+)(?:.*?;\s+\bAge=(?<Age>\d+))?";
foreach (var str in strs) 
{
    var result = Regex.Match(str, pattern);
    if (result.Success)
    {
        Console.WriteLine("Name: \"{0}\", Age: \"{1}\"", result.Groups["Name"].Value, result.Groups["Age"].Value);
    }
}

See this C# demo

The (?:\bName=(?<Name>[^;]+).*?;\s+)?\bAge=(?<Age>\d+)|\bName=(?<Name>[^;]+)(?:.*?;\s+\bAge=(?<Age>\d+))? has 2 branches:

  • (?:\bName=(?<Name>[^;]+).*?;\s+)?\bAge=(?<Age>\d+) - the Name part is optional, Age is compulsory
  • | - or
  • \bName=(?<Name>[^;]+)(?:.*?;\s+\bAge=(?<Age>\d+))? - the Age part is optional, Name is compulsory

Upvotes: 1

Gusdor
Gusdor

Reputation: 14334

Here is the regex you want. (?<Key>\w+?)=(?<Value>(?:\w|\s)+);

This pattern captures key/value pairs into the named groups Key and Value.

This solution will fail to function correctly if a key name contains a space.

C# Usage

using System;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;

public class Test
{
    public static void Main()
    {
        string input = @"aaa bbbb; Name=John Lewis; ccc ddd; Age=20;";
        string pattern = @"(?<Key>\w+?)=(?<Value>(?:\w|\s)+);";

        var matches = Regex.Matches(input, pattern);
        foreach (var match in matches.OfType<Match>())
        {
            string key = match.Groups["Key"].Value;
            string value = match.Groups["Value"].Value;
            Console.WriteLine(key + ": " + value);
        }
    }
}

Output

Name: John Lewis
Age: 20

Upvotes: 1

DarkSquirrel42
DarkSquirrel42

Reputation: 10257

...

.*?(?:Name=(?'name'[^;]*);)*.*?(?:Age=(?'age'\d*);)*

Upvotes: 0

Paweł Hemperek
Paweł Hemperek

Reputation: 1180

(?'name'\w+)[=]{1}(?'value'[\w ]+)

This Regex will give you name and value groups. In name you'll have Name or Age and in value John Lewis or 20

You can see how it works here.

Upvotes: 0

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