Deserialization with System.Text.Json in .NET Core 3.1 results in null property values

Question

I have the following json:

{
 "GameConfig":{
  "TeamConstraint":{
     "SameTeamPlayers":[
        "Raghav",
        "Surya"
     ],
     "OppositeTeamPlayers":[
        "Wolfman",
        "Pawan"
     ]
  },
  "Players":[
     "Tramp",
     "Surya",
     "Raghav",
     "Krishna",
     "Sanjay",
     "Bala",
     "Wolfman",
     "Eagle",
     "Sai",
     "Pawan",
     "Joo",
     "Srikanth"
  ],
  "Ranks":{
     "Tramp":10,
     "Surya":10,
     "Raghav":8,
     "Krishna":8,
     "Eagle":8,
     "Sai":8,
     "Sanjay":7.5,
     "Pawan":5,
     "Wolfman":5.0,
     "Srikanth":6,
     "Bala":4.5,
     "Joo":1.5
   }
  }
}

I am writing a simple console app .NET Core 3.1. I have tried both the JSON.NET as well as the new MSFT System.Text.Json deserializer. But I get only null values for all of the properties with the following Model object.

[Serializable]
public class GameConfig
{
    public TeamConstraint TeamConstraint { get; set; }
    
    public List<string> Players { get; set; }
    
    public Dictionary<string, double> Ranks { get; set; }
}

[Serializable]
public class TeamConstraint
{
    public List<string> OppositeTeamPlayers { get; set; }

    public List<string> SameTeamPlayers { get; set; }
}

I have tried several additional options like using a contract resolver with CamelCase properties and changing the code and json accordingly but nothing has worked so far. What am I missing?

This is the code I am using to deserialize.

var jsonString = File.ReadAllText(TeamGeneratorStandardSettings.Default.GameConfigFile);
var gameConfig = JsonSerializer.Deserialize<GameConfig>(jsonString);

Answer 1

You are trying to deserialize into GameConfig , whereas that is simply a top-level property of your overall json object structure. You need a new top-level type to deserialize into that contains your GameConfig object.

public class GameData
{
    public GameConfig GameConfig { get; set; } 
}

var jsonString = File.ReadAllText(TeamGeneratorStandardSettings.Default.GameConfigFile);
var gameConfig = JsonSerializer.Deserialize<GameData>(jsonString);

Alternatively, you could remove the wrapping object from your json and still deserialize directly to a GameConfig object:

{
  "TeamConstraint":{
     "SameTeamPlayers":[
        "Raghav",
        "Surya"
     ],
     "OppositeTeamPlayers":[
        "Wolfman",
        "Pawan"
     ]
  },
  "Players":[
     "Tramp",
     "Surya",
     "Raghav",
     "Krishna",
     "Sanjay",
     "Bala",
     "Wolfman",
     "Eagle",
     "Sai",
     "Pawan",
     "Joo",
     "Srikanth"
  ],
  "Ranks":{
     "Tramp":10,
     "Surya":10,
     "Raghav":8,
     "Krishna":8,
     "Eagle":8,
     "Sai":8,
     "Sanjay":7.5,
     "Pawan":5,
     "Wolfman":5.0,
     "Srikanth":6,
     "Bala":4.5,
     "Joo":1.5
   }
  }

var jsonString = File.ReadAllText(TeamGeneratorStandardSettings.Default.GameConfigFile);
var gameConfig = JsonSerializer.Deserialize<GameConfig>(jsonString);