Here is a solution using Microsoft's System.Text.Json library:
static string FormatJsonText(string jsonString)
{
using var doc = JsonDocument.Parse(
jsonString,
new JsonDocumentOptions
{
AllowTrailingCommas = true
}
);
MemoryStream memoryStream = new MemoryStream();
using (
var utf8JsonWriter = new Utf8JsonWriter(
memoryStream,
new JsonWriterOptions
{
Indented = true
}
)
)
{
doc.WriteTo(utf8JsonWriter);
}
return new System.Text.UTF8Encoding()
.GetString(memoryStream.ToArray());
}