C#: Parsing a non-JSON array-only api response to

问题:

I have a response from some Rest API that just returns some array of arrays like the following:

[
[123,"0.01","0.02","0.03","0.04","12345.00000",123456789,"300.000",4000,"123.000","456.000","0"],
[456,"0.04","0.03","0.02","0.01","54321.00000",987654321,"500.000",4000,"123.000","456.000","1"],
[789,"0.05","0.06","0.07","0.08","12345.00000",123456789,"700.000",8000,"456.000","123.000","0"]    
]

In this example, the amount of datasets is 3, but the amount is always different and could be 100+ also.

I want to have this read out into a class object, which has 12 arrays according to each type of value shown in the response:

public class foo
{
    ...
    public int[] firstParam;
    public string[] secondParam;
    public string[] thirdParam;

    ...        
}

For example, firstParam should contain then {123,456,789}; secondParam should contain {"0.01","0.04","0.05"} and so on.

The schema for the columns is known and documented in Public Rest API for Binance: Kline/Candlestick data.. An example would be some query like https://api.binance.com/api/v1/klines?symbol=XVGBTC&interval=1h

回答1:

The API response is perfectly valid JSON; it is a jagged 2d array of primitive values where the columns have specific meanings as defined in the Public Rest API for Binance: Kline/Candlestick data. As such it can be parsed and deserialized using json.net, e.g. as an object [][]:

var arrays = JsonConvert.DeserializeObject<object [][]>(jsonString);

(Sample working .Net fiddle #1.)

However, rather than deserializing the JSON into a jagged 2d object array or (as you suggest in your question) a single root object with array properties corresponding to column values, I would recommend that you design a class BinanceKlineData that represents a single row of values for those specific columns, then deserialize into a List<BinanceKlineData> using the custom JsonConverter ObjectToArrayConverter<BinanceKlineData> from C# JSON.NET - Deserialize response that uses an unusual data structure.

Firstly, using the documented meanings of the columns, you can define your type BinanceKlineData as follows:

public class BinanceKlineData
{
    [JsonProperty(Order = 1)]
    public long OpenTime { get; set; }
    [JsonProperty(Order = 2)]
    public decimal Open { get; set; } // Or string, if you prefer
    [JsonProperty(Order = 3)]
    public decimal High { get; set; } // Or string, if you prefer
    [JsonProperty(Order = 4)]
    public decimal Low { get; set; } // Or string, if you prefer
    [JsonProperty(Order = 5)]
    public decimal Close { get; set; } // Or string, if you prefer
    [JsonProperty(Order = 6)]
    public decimal Volume { get; set; } // Or string, if you prefer
    [JsonProperty(Order = 7)]
    public long CloseTime { get; set; }
    [JsonProperty(Order = 8)]
    public decimal QuoteAssetVolume { get; set; } // Or string, if you prefer
    [JsonProperty(Order = 9)]
    public long NumberOfTrades { get; set; } // Should this be an long or a decimal?
    [JsonProperty(Order = 10)]
    public decimal TakerBuyBaseAssetVolume { get; set; }
    [JsonProperty(Order = 11)]
    public decimal TakerBuyQuoteAssetVolume { get; set; }
    // public string Ignore { get; set; }
}

Notice that I have annotated the properties with [JsonProperty(Order = N)]. This order corresponds to the order of the columns in the Rest API, and will be used to inform Json.NET how to map columns to properties by column index. Notice also that I modeled the numeric columns as decimal despite the fact that they appear as strings in the JSON. You could use string if you prefer a more literal deserialization.

Next, grab the generic ObjectToArrayConverter<T> from this answer. It has logic to make use of the Order = N metadata to map row values to member values in the generic type T by column index.

Finally, you will be able to deserialize the JSON as a List<BinanceKlineData> as follows:

var settings = new JsonSerializerSettings
{
    Converters = { new ObjectToArrayConverter<BinanceKlineData>() },
};

var root = JsonConvert.DeserializeObject<List<BinanceKlineData>>(jsonString, settings);

Sample working .Net fiddle #2.

Or if you prefer you could apply the converter directly to BinanceKlineData as follows:

[JsonConverter(typeof(ObjectToArrayConverter<BinanceKlineData>))]
public class BinanceKlineData
{
    // Remainder as before
}

When the converter is applied directly to the type it is no longer necessary to pass it in via JsonSerializerSettings.Converters.

Sample fiddle #3.

回答2:

Depending on exactly how the response is formatted you might be able to do something like this:

var s = "[[123,\"0.01\",\"0.02\",\"0.03\",\"0.04\",\"12345.00000\",123456789,\"300.000\",4000,\"123.000\",\"456.000\",\"0\"],[456,\"0.04\",\"0.03\",\"0.02\",\"0.01\",\"54321.00000\",987654321,\"500.000\",4000,\"123.000\",\"456.000\",\"1\"],[789,\"0.05\",\"0.06\",\"0.07\",\"0.08\",\"12345.00000\",123456789,\"700.000\",8000,\"456.000\",\"123.000\",\"0\"]]";

var lines = s.Split(new char[] { '[', ']' }, StringSplitOptions.RemoveEmptyEntries).Select(a => a.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries).Select(b => b.TrimEnd('"').TrimStart('"')).ToArray()).Where(a => a.Any());

var c = lines.Count();

var foo = new foo
{
    firstParam = new int[c],
    secondParam = new string[c],
    thirdParam = new string[c]
};

for (int i = 0; i < c; i++)
{
    foo.firstParam[i] = Int32.Parse(lines.ElementAt(i)[0]);
    foo.secondParam[i] = lines.ElementAt(i)[1];
    foo.thirdParam[i] = lines.ElementAt(i)[2];
}

Console.WriteLine(string.Join(", ", foo.firstParam)); \\123, 456, 789
Console.WriteLine(string.Join(", ", foo.secondParam)); \\0.01, 0.04, 0.05
Console.WriteLine(string.Join(", ", foo.thirdParam)); \\0.02, 0.03, 0.06