String Functions in JSONPath

I'm using Json.Net's SelectToken method to query JSON using JSONPath with expressions like:

JToken acme = o.SelectToken("$.Manufacturers[?(@.Name == 'Acme Co')]");

-- http://www.newtonsoft.com/json/help/html/QueryJsonSelectTokenJsonPath.htm

Does JSONPath support XPath style String Functions?
By String Functions, I mean those described in How to use like in XPath?

For example, is there syntax for the contains() method?

I've tried:

o.SelectToken("$.Manufacturers[?(contains(@.Name, 'Acme')]");

but JSON.Net complains of a syntax error (it doesn't like contains).

Solution

Json.NET Release 11 introduced the regex operator =~ for JSONPath queries. Using it you can do string pattern matching including contains() matches. For example:

To match a value containing the string Acme use =~ /Acme/:

o.SelectToken("$.Manufacturers[?(@.Name =~ /Acme/)]")

To match a value containing the word Acme, bracket it with \b:

o.SelectToken("$.Manufacturers[?(@.Name =~ /\\bAcme\\b/)]")

To do a case-insensitive match on a string containing acme, preface the case-insensitive portion with (?i):
```
o.SelectToken("$.Manufacturers[?(@.Name =~ /(?i)acme/)]")
```
(?-i) ends case-insensitive matching.
To match a value that does not contain Acme, use =~ /^(?!.*Acme).*$/):
```
o.SelectToken("$.Manufacturers[?(@.Name =~ /^(?!.*Acme).*$/)]")
```
See: C# Regex to match a string that doesn't contain a certain string?.
To match strings starting with Acme, insert ^ at the beginning of the regex:
```
o.SelectToken("$.Manufacturers[?(@.Name =~ /^Acme/)]")
```
To match strings ending with Acme, add $ at the end of the regex:
```
o.SelectToken("$.Manufacturers[?(@.Name =~ /Acme$/)]")
```
To match strings with a specified length N, use =~ /(?s)^.{N}$/):
```
o.SelectToken("$.Manufacturers[?(@.Name =~ /(?s)^.{7}$/)]")
```
Here (?s) specifies single line mode (which forces newlines to be included in the character count), . matches any character, the quantifier .{7} requires exactly 7 matches of the preceding token ., and ^ and $ match the beginning and end of the string (which prevents the regex from matching strings longer than 7 characters).

Demo fiddle here.