using System;

using System.Text.Json;

using System.Text.Json.Serialization;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var emptyJson = 

            """

{

    "values": []

}

""";

        var nonEmptyJson = 

            """

{

    "values": {

        "key1": "value1",

        "key2": "value2"

    }

}

""";

        var emptyResult = JsonSerializer.Deserialize<Model>(emptyJson);

        var nonEmptyResult = JsonSerializer.Deserialize<Model>(nonEmptyJson);

        emptyResult.Dump();

        nonEmptyResult.Dump();

    }

}

​

public class Model

{

    [JsonPropertyName("values")]

    public Dictionary<string,string> Values {get;set;} = new();

    //public List<KeyValuePair<string,string>> Values {get;set;}

}