Invex.Extensions.Json

Invex.Extensions.Json is a small, allocation-conscious library for flattening, unflattening, and updating System.Text.Json node trees (JsonNode, JsonObject, and JsonArray) with readable paths such as user:address:city.

It is useful for configuration and environment-variable adapters, ETL pipelines, JSON diffing or patching, and exchanging JSON with flat key/value stores.

Features

• Flatten any JsonNode into path/value pairs.
• Rebuild a JsonObject from flattened pairs.
• Replace one or many values in an existing JsonObject, including array elements.
• Preserve JSON value types when flattening to a JsonObject.
• Use configurable separators, including multi-character separators.
• Avoid reflection and regular expressions on the hot paths.
• Target net10.0, net9.0, net8.0, and netstandard2.0.

Installation

dotnet add package Invex.Extensions.Json

The package exposes the Invex.Extensions.Json namespace. The netstandard2.0 target includes a System.Text.Json package dependency.

Quick start

using System.Text.Json.Nodes;
using Invex.Extensions.Json;

var json = JsonNode.Parse("""
{
  "user": {
    "name": "John",
    "tags": ["admin", "user"]
  }
}
""")!;

// String-valued flattening uses bracketed array indices.
IDictionary<string, string?> flat = JsonExtensions.Flatten(json);
// user:name       = "John"
// user:tags:[0]   = "admin"
// user:tags:[1]   = "user"

// The matching operation rebuilds the hierarchy.
JsonObject rebuilt = JsonExtensions.Unflatten(flat);

// Replacements mutate the existing object and use bare numeric indices.
rebuilt.ReplaceValues(new Dictionary<string, string?>
{
    ["user:name"] = "Jane",
    ["user:tags:1"] = "editor",
});

Choose an API surface

The library has two complementary path and value models. Pair operations from the same column when round-tripping.

	JsonExtensions	JsonObject extension members
Flattening input	Any JsonNode	JsonObject
Array path syntax	Bracketed: users:[0]:name	Bare numeric: users:0:name
Flattened values	string?	Original JSON nodes, or string? for the dictionary method
Unflattened arrays	Append order; no sparse padding	Numeric indices; sparse indices padded with null
Best suited to	Configuration and string key/value stores	Lossless JSON round-tripping

String-valued operations

JsonExtensions.Flatten returns an IDictionary<string, string?>, where JSON null is represented by a null value. JsonExtensions.Unflatten creates a new JsonObject, but every non-null leaf becomes a JSON string; numbers and booleans are not restored to their original JSON kinds.

Array indices in Unflatten are applied in the order encountered in the input. The method appends values rather than padding arrays to the numeric index. Empty objects and arrays produce no flattened entries and therefore cannot be represented by a flattened result.

Type-preserving JsonObject operations

var source = JsonNode.Parse(
    """{ "a": { "number": 42, "enabled": true, "items": [null, "x"] } }""")!
    .AsObject();

JsonObject flatObject = source.ToFlattenedJsonObject();
// a:number = 42, a:enabled = true, a:items:0 = null, a:items:1 = "x"

JsonObject roundTrip = flatObject.ToUnflattenedJsonObject();
Dictionary<string, string?> flatDictionary = source.ToFlattenedDictionary();
bool hasNestedValues = source.HasNestedObjects();

ToFlattenedJsonObject deep-clones leaf nodes, and ToUnflattenedJsonObject deep-clones them again, so these operations do not share mutable node references with their source. ToFlattenedDictionary stringifies values and cannot preserve their JSON kinds. HasNestedObjects checks only direct property values; it returns true for a direct JsonObject or JsonArray.

Replacing values

ReplaceValue and ReplaceValues modify the supplied JsonObject in place and return the same instance. Replacement values are always stored as JSON strings, or as JSON null when the supplied value is null.

ReplaceValue supports nested object paths but does not interpret array segments. A simple root-level path is replaced only when that property already exists. For a separated path, existing object segments are traversed; if a segment is missing, traversal stops at the deepest object reached and the final path segment is assigned there. If no object segment exists, that final segment is assigned on the root object.

ReplaceValues additionally supports existing arrays using bare, zero-based numeric segments such as users:0:name. It never creates intermediate objects or arrays. A missing or out-of-bounds path is left unchanged unless the document contains the applicable documented literal-path fallback. Empty keys are ignored, and [0] is a literal property name rather than an array index.

See Replacing values for the complete traversal and fallback rules.

Separators and path notation

All path-based methods accept a separator, defaulting to ":". Separators can contain multiple characters:

var flat = JsonExtensions.Flatten(json, separator: "__");
var rebuilt = JsonExtensions.Unflatten(flat, separator: "__");

Use the same separator for both halves of a round trip, and avoid separators that occur in property names. Property names are not escaped; a separator in a property name will be interpreted as a path boundary when unflattening.

The two array conventions are intentionally different:

• JsonExtensions.Flatten and Unflatten use [0], [1], and so on.
• JsonObject extension members and ReplaceValues use 0, 1, and so on.

Do not pass bracketed paths from Flatten directly to ReplaceValues, and do not mix JsonExtensions.Unflatten with ToFlattenedJsonObject.

Documentation

Topic	Description
Getting started	Installation, namespaces, and guided examples
Path notation	Array conventions, separators, values, and edge cases
Flattening and unflattening	JsonExtensions.Flatten and Unflatten
JsonObject extension members	Type-preserving flattening and reconstruction
Replacing values	In-place updates, arrays, and fallbacks
API reference	Generated DocFX API documentation

License

Licensed under the MIT License.