JSONPath Functions

JsonPath expressions support basic method calls.

Method	Description	Example
length()	Returns the length of an array or string.	$.store.book[?(length(@.title) > 5)]
count()	Returns the count of matching elements.	$.store.book[?(count(@.authors) > 1)]
match()	Returns true if a string matches a regular expression.	$.store.book[?(match(@.title,'.*Century.*'))]
search()	Searches for a string within another string.	$.store.book[?(search(@.title,'Sword'))]
value()	Accesses the value of a key in the current object.	$.store.book[?(value(@.price) < 10)]

JSONPath Extensions Functions

You can extend the supported function set by registering your own functions.

Example: Implement a JsonNode Path Function:

Step 1: Create a custom function that returns the path of a JsonNode.

public class PathNodeFunction() : ExtensionFunction( PathMethod, CompareConstraint.MustCompare )
{
    public const string Name = "path";
    private static readonly MethodInfo PathMethod = GetMethod<PathNodeFunction>( nameof( Path ) );

    private static ScalarValue<string> Path( IValueType argument )
    {
        return argument.TryGetNode<JsonNode>( out var node ) ? node?.GetPath() : null;
    }
}

Step 2: Register your custom function.

JsonTypeDescriptorRegistry.GetDescriptor<JsonNode>().Functions
    .Register( PathNodeFunction.Name, () => new PathNodeFunction() );

Step 3: Use your custom function in a JSONPath query.

var results = source.Select( "$..[?path(@) == '$.store.book[2].title']" );