C# JSON file into list

Question

In my C# + WPF + .NET 4.5 code, suppose I have defined a Player class in the following manner:

public class Player {
  public string FirstName;
  public string LastName;
  public List<int> Cells;
  public string Level;
}

And I have a myobjects.json file in which I managed to write (using JSON.NET) a serialized collection of these objects (first two shown below):

{
  "FirstName": "Foo",
  "LastName": "Fighter",
  "Cells": [
    1,
    2,
    3
  ],
  "Level": "46"
}{
  "FirstName": "Bar",
  "LastName": "Baz",
  "Cells": [
    104,
    127,
  ],
  "Level": "D2"
}

What I would like to do is to read the file, and deserialize these objects and populate a List of Players:

using (Stream fs = openDialog.OpenFile())
using (StreamReader sr = new StreamReader(fs))
using (JsonTextReader jr = new JsonTextReader(sr)) {
  while (jr.Read()) {
    /* Find player in file */
    Player p = /* Deserialize */
    PlayerList.Add(p);
  }
}

I4V · Accepted Answer · 2013-05-07 10:14:16Z

35

No need to read item by item.

string json = File.ReadAllText("myobjects.json");
var playerList = JsonConvert.DeserializeObject<List<Player>>(json);

You can use this code to write your player list to file

File.WriteAllText("myobjects.json", JsonConvert.SerializeObject(playerList));

answered May 7, 2013 at 10:14

I4V

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3 Comments

mbaytas Over a year ago

Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[MyApp.Player]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly. To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List<T>) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.

I4V Over a year ago

@baytas First, use the serialization code File.WriteAllText... and compare the result with yours. Most probably you are not forming a correct json array. (For ex, the json in your question misses a comma between objects.)

CodeHacker Over a year ago

Just for the sake of completion: The objects must be enclosed in [ ] so it's an array, and the objects must be separated by comas [{"firstName":"value1"},{"firstName":"value1"}]

R M Shahidul Islam Shahed · Accepted Answer · 2019-10-24 19:48:53Z

3

In C# .Net core console application: First, install Newtonsoft from NuGet by the following command.

PM> Install-Package Newtonsoft.Json -Version 12.0.2

    string filePath = Path.GetFullPath(Path.Combine(Environment.CurrentDirectory, @"..\..\..\")) + @"Data\Country.json";
    string _countryJson = File.ReadAllText(filePath);
    var _country = JsonConvert.DeserializeObject<List<Country>>(_countryJson);

answered Oct 24, 2019 at 19:48

R M Shahidul Islam Shahed

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