todynamic(), parse_json()

Interprets a string as a JSON value and returns the value as dynamic.


The todynamic() and parse_json() functions are interpreted equivalently.

This function is better than extractjson() function when you need to extract more than one element of a JSON compound object. Prefer using dynamic() when possible.


parse_json(json) todynamic(json)


  • json: An expression of type string. It represents a JSON-formatted value, or an expression of type dynamic, representing the actual dynamic value.


An object of type dynamic that is determined by the value of json:

  • If json is of type dynamic, its value is used as-is.
  • If json is of type string, and is a properly formatted JSON string, then the string is parsed, and the value produced is returned.
  • If json is of type string, but it isn't a properly formatted JSON string, then the returned value is an object of type dynamic that holds the original string value.


In the following example, when context_custom_metrics is a string that looks like this:


then the following CSL Fragment retrieves the value of the duration slot in the object, and from that it retrieves two slots, duration.value and duration.min (118.0 and 110.0, respectively).

| extend d=parse_json(context_custom_metrics) 
| extend duration_value=d.duration.value, duration_min=d["duration"]["min"]


It's common to have a JSON string describing a property bag in which one of the "slots" is another JSON string.

For example:

let d='{"a":123, "b":"{\\"c\\":456}"}';
print d

In such cases, it isn't only necessary to invoke parse_json twice, but also to make sure that in the second call, tostring is used. Otherwise, the second call to parse_json will just pass on the input to the output as-is, because its declared type is dynamic.

let d='{"a":123, "b":"{\\"c\\":456}"}';
print d_b_c=parse_json(tostring(parse_json(d).b)).c