String Functions in JSONPath

Question

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).

If by "JSONPath" you mean "the JSONPath supported by SelectToken and SelectTokens in Json.NET", the answer looks to be "no". If it did, there would be an appropriate ScanFilter here, but there isn't. QueryFilter is closest but QueryExpression doesn't have it. — dbc
– dbc, Commented Dec 10, 2015 at 0:22
@dbc - Thanks for checking the source. I guess you're saying if I want it, I'll need to build it? — Philip Pittle
– Philip Pittle, Commented Dec 10, 2015 at 1:16

dbc · Accepted Answer · 2023-08-07 19:36:07Z

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.

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