Regex to Match Json array element in C#

Question

I need to match element of the JSON array element in c# for filter autocomplete in c#. Here is my code:

string firstname = "h";
List<user> userlist = new List<user>();
user user1 = new user();
user1.firstname = "Hardik";
user1.lastname = "Gondalia";
userlist.Add(user1);

user user2 = new user();
user2.firstname = "John";
user2.lastname = "Abraham";
userlist.Add(user2);

user user3 = new user();
user3.firstname = "Will";
user3.lastname = "Smith";
userlist.Add(user3);

user user4 = new user();
user4.firstname = "Martin";
user4.lastname = "Luthor";
userlist.Add(user4);

var myRegex = new Regex(".*\\b" + firstname + "\\b.*");
var u = userlist.Where(i => myRegex.IsMatch(i.firstname)).ToList();
return Json(u, JsonRequestBehavior.AllowGet);

When I pass character "h" as firstname, I am getting count of u = 0; I am expecting user1 and user2 in variable u.

_"I am expecting user1 and user2"_ - why? `\bh\b` will only match the lone standing `h` because of the "word boundary" `\b`... Perhaps start by reading a regex tutorial. — CodeCaster, Aug 03 '16 at 10:11
Well, these first names do not contain `h` as a whole word. And `Hardik` contains an uppercase `H` (pass `RegexOptions.IgnoreCase` flag to `myRegex`). Also, `Regex.IsMatch` also finds partial matches, you do not need `.*` in your pattern at all. Judging by the code, you may achieve that without a regex, use `userlist.Where(i => culture.CompareInfo.IndexOf(i.firstname, firstname, CompareOptions.IgnoreCase) >= 0).ToList()` (see http://stackoverflow.com/questions/444798/case-insensitive-containsstring) — Wiktor Stribiżew, Aug 03 '16 at 10:12
@CodeCaster : you mean to say that \b will match whole word rather then individual character? — Ubiquitous Developers, Aug 03 '16 at 10:14
@zerkms : I thought regex was good alternative. Any other approach is most welcome. — Ubiquitous Developers, Aug 03 '16 at 10:18
@UbiquitousDevelopers a good alternative to *what*? Why not `String.Contains`? — zerkms, Aug 03 '16 at 10:19
@zerkms : I don't know how to user String.Contains with list of class. — Ubiquitous Developers, Aug 03 '16 at 10:21

Wiktor Stribiżew · Accepted Answer · 2017-09-25T07:11:04.633

I am posting an answer since there are several issues here.

First, these first names do not contain h as a whole word and you defined \b in your pattern to match a first name as a whole word.

Second, Hardik contains an uppercase H (so, you should consider passing RegexOptions.IgnoreCase flag to myRegex).

Third, Regex.IsMatch also finds partial matches, you do not need .* in your pattern at all.

Judging by the code, you may achieve that without a regex, use

userlist.Where(i => culture.CompareInfo.IndexOf(i.firstname, firstname, CompareOptions.IgnoreCase) >= 0).ToList()

Regex to Match Json array element in C#

1 Answers1