Extracting specific JSON out of large string using C# Regex

Question

Here's a sample string:

Lorem ipsum dolor sit amet, ad eam option suscipit invidunt, ius propriae detracto cu. Nec te wisi lo{"firstName":"John", "lastName":"Doe"}rem, in quo vocent erroribus {"firstName":"Anna", "lastName":"Smith"}dissentias. At omittam pertinax senserit est, pri nihil alterum omittam ad, vix aperiam sententiae an. Ferri accusam an eos, an facete tractatos moderatius sea{"firstName":"Peter", "lastName":"Jones"}. Mel ad sale utamur, qui ut oportere omittantur, eos in facer ludus dicant.

Assume the following data model exists:

public class Person
{
   public string firstName;
   public string lastName;
}

How could I use regex to extract JSON out of this text and create a List<Person> with:

{"firstName":"John", "lastName":"Doe"},
{"firstName":"Anna", "lastName":"Smith"},
{"firstName":"Peter", "lastName":"Jones"}

Objects can be buried anywhere in the string, so their position relative to words, letters, punctuations, whitespaces, etc. does not matter. If the above JSON notation is broken, simply ignore it. The following would be invalid:

{"firstName":"John", "middleName":"", "lastName":"Doe"},
{"firstName":"Anna", "lastName":"Smith", "age":""},
{"firstName":"Peter", "lastName":"Jones" some text}

In other words, pattern search must be strict to the following:

{"firstName":"[val]", "lastName":"[val]"}

Does it have to be a Regex? It might be easier to just do this with procedural code. — Matthew Haugen
– Matthew Haugen, Commented Jan 30, 2016 at 5:46
You shouldn't use Regex with hierarchical data like JSON for the same reasons as XML — user585968
– user585968, Commented Jan 30, 2016 at 5:47
To Micky's point, is it legal to have nested JSON objects? I'd assume so, depending on where this is coming from. Or, equally frustrating, I assume you could have a string that contains a curly brace? Nobody would have a name with one, I assume, but it'd be totally valid JSON. — Matthew Haugen
– Matthew Haugen, Commented Jan 30, 2016 at 5:48
Nested objects aren't a concern at the moment. Ah, never thought about curly braces in the middle. I could instead use another symbol or substring and disallow the user from inputting it. — Mark13426
– Mark13426, Commented Jan 30, 2016 at 5:51

Travis Schettler · Accepted Answer · 2016-01-30 06:14:50Z

1

Here's a regex that you could use to extract the values:

({\s*"firstName":\s*"[^"]+",\s*"lastName":\s*"[^"]+"\s*})

After this, I'd suggest just using Json.NET to deserialize the objects.

edited Jan 30, 2016 at 6:14

answered Jan 30, 2016 at 5:51

Travis Schettler

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4 Comments

Mark13426 Over a year ago

Just to clarify, is this simply (opening curly brace + any number of characters that are not closing curly brace + closing curly brace)? What if there was another opening curly brace in between? Also, firstName and lastName should be hard-coded.

Mark13426 Over a year ago

This doesn't seem to return matches for me. Are the parentheses needed? Also, there is a space after the comma.

Travis Schettler Over a year ago

The parentheses are what returns the matches. The \s matches spaces. This is just the regex, you'll have to properly escape the backslashes and quotes in your C# string. Here's proof it is working: regex101.com/r/rO7bK2/1

Mark13426 Over a year ago

Great. I was able to figure out escaping!

Kutty Rajesh Valangai · Accepted Answer · 2016-01-30 06:06:16Z

use this code snippet,

//Take All first Name
    string strRegex1 = @"firstName"":""([^""""]*)"",";
//Take All Last Name
    string strRegex2 = @"lastName"":""([^""""]*)""";
    Regex myRegex = new Regex(strRegex, RegexOptions.None);
   Regex myRegex2 = new Regex(strRegex2, RegexOptions.None);
    string strTargetString = @"{""firstName"":""John"", ""middleName"":"""", ""lastName"":""Doe""}," + "\n" + @"{""firstName"":""Anna"", ""lastName"":""Smith"", ""age"":""""}," + "\n" + @"{""firstName"":""Peter"", ""lastName"":""Jones"" some text}";

    foreach (Match myMatch in myRegex.Matches(strTargetString))
    {
      if (myMatch.Success)
      {
       // Add your code here for First Name
      }
    }

foreach (Match myMatch in myRegex2.Matches(strTargetString))
    {
      if (myMatch.Success)
      {
        // Add your code herefor Last Name
      }
    }

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