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NuGet

Liersch.Json - JSON Support for .NET

Liersch.Json is a small .NET library for parsing and generating JSON documents. The library is written in C# 3.0 supporting the following .NET platforms:

  • from .NET Framework 2.0
  • from .NET Core 1.0
  • from .NET Standard 1.0
  • Mono
  • .NET Micro Framework 4.4

The file size of the compiled library is only ≈25 kB. All major changes are logged in the CHANGELOG.md file.

Getting Started

The easiest and the fastest way to integrate the library into a project is to use the Liersch.Json package published on NuGet. For older projects (before .NET Framework 4.0) the library has to be compiled and integrated manually. In order to compile the project for the outdated .NET Micro Framework, the compiler symbol NETMF must be defined in addition.

Migration from Version 1.x

  • The type name prefix SL used in version 1.x has been removed in version 2.x.
  • The reflection-based classes have been moved to the new Liersch.JsonSerialization library.

Parsing JSON Documents

The static function JsonNode.Parse should be used to parse JSON document in restrictive mode. The input document should be formatted correctly. Otherwise a JsonException is thrown.

For less restrictive parsing an instance of JsonParser must be created. There are different properties to configure the parsing mode. In JSON documents, strings must be delimited by double-quotation marks. The parser also accepts single-quotation marks if property AreSingleQuotesAllowed is true.

public static void RunExample1()
{
  string json=@"
  {
    ""addressBook"": [
      {""lastName"": ""Average"", ""firstName"": ""Joe""},
      {""lastName"": ""Doe"", ""firstName"": ""Jane""},
      {""lastName"": ""Smith"", ""firstName"": ""John""}
    ]
  }";

  var root=JsonNode.Parse(json);
  JsonNode book=root["addressBook"];
  if(book.IsArray)
  {
    int c=book.Count;
    for(int i=0; i<c; i++)
    {
      JsonNode entry=book[i];
      string ln=entry["lastName"];
      string fn=entry["firstName"];
      Console.WriteLine(fn+" "+ln);
    }
  }
}

JsonNode Class

The parser result is an instance of JsonNode. It can be used to process the parsed JSON document. JsonNode implements IEnumerable to enumerate all sub nodes for arrays and objects. In addition there is the property Names that can be used for objects to enumerate all property names.

public static void RunExample2()
{
  string json=RetrieveJsonExample();
  PrintNode(JsonNode.Parse(json), "demo = ", 0);
}

static void PrintNode(JsonNode node, string prefix, int level)
{
  Console.Write(new string(' ', level*2));
  Console.Write(prefix);

  switch(node.NodeType)
  {
    case JsonNodeType.Array:
      Console.WriteLine("(Array)");
      int c=node.Count;
      for(int i=0; i<c; i++)
        PrintNode(node[i], "["+i.ToString(CultureInfo.InvariantCulture)+"] = ", level+1);
      break;

    case JsonNodeType.Object:
      Console.WriteLine("(Object)");
      foreach(string name in node.Names)
        PrintNode(node[name], name+" = ", level+1);
      break;

    case JsonNodeType.Boolean:
    case JsonNodeType.Number:
    case JsonNodeType.String:
      Console.WriteLine(node.AsString+" ("+node.NodeType.ToString()+")");
      break;

    default:
      Console.WriteLine("("+node.NodeType.ToString()+")");
      break;
  }
}

The following properties can be used to read and write values: AsBoolean, AsInt32, AsInt64, AsDouble and AsString. If on reading a property, the value cannot be converted to the corresponding data type, the default value of the data type is returned instead.

If accessing a missing object or if using an invalid array index, no exception is thrown. Instead an empty node is returned. If a value setter is used for a not existing value, the value is created. JsonNode can also be used to create new JSON documents.

public static void RunExample3()
{
  var root=new JsonNode();
  root["addressBook"]=CreateAddressBook();
  Console.WriteLine(root.AsJson);
}

static JsonNode CreateAddressBook()
{
  var book=new JsonNode();

  book[0]["LastName"]="Average";
  book[0]["firstName"]="Joe";

  book[1]["LastName"]="Doe";
  book[1]["firstName"]="Jane";

  book[2]["LastName"]="Smith";
  book[2]["firstName"]="John";

  return book;
}

JsonMonitor Class

The JsonNode.CreateMonitor function can be used to create an instance of class JsonMonitor. It's only allowed for root nodes and it must not be called several times.

JsonMonitor.IsModified is set to true on any change. JsonMonitor.IsReadOnly can be used to disallow changing any node. If passing root nodes to external code, this property can be used to avoid unexpected side effects.

JsonWriter Class

The writer class JsonWriter has a very small footprint. It has a good performance, but no checks for incorrect use.

License

The software is published under the conditions of an open source license. Alternatively, other terms can be agreed under a commercial license. You can support the maintenance and further development of the software with a voluntary donation.

Copyright

Copyright © 2013-2021 Steffen Liersch
https://www.steffen-liersch.de/

Links

The source code is maintained on GitHub:
https://github.com/steffen-liersch/Liersch.Json

Packages can be downloaded through NuGet:
https://www.nuget.org/packages/Liersch.Json