How to get DataTable from JSON string that contains an empty array using JsonConvert?

Question

(Json.NET) JsonConvert.DeserializeObject<DataTable>() works with a populated array but, not with an empty array ( [], as seen in my example: jsonString2 → col2 ). I would like it to create a string[] column by default, or skip, or otherwise avoid the exception.

Screenshot:

Code (Update 1: Removed extra comma after col3 and still getting exception.):

[TestMethod]
public void TestSerializeEmptyArray()
{
    var jsonString1 = @"[
        {
            ""col1"": ""bd3013bb-39a3-4704-b7c9-803c220f8abe"",
            ""col2"": [
            ""57ae6e0e-0c20-4da5-a246-b949c71ef551"",
            ""2bafe349-4b29-4161-814a-5a369459b78c""
                ],
            ""col3"": ""b2c172ea-e48c-4e20-9bee-3470278bd801""
        }]";
    var test1 = JsonConvert.DeserializeObject<DataTable>(jsonString1);

    var jsonString2 = @"[
        {
            ""col1"": ""bd3013bb-39a3-4704-b7c9-803c220f8abe"",
            ""col2"": [],
            ""col3"": ""b2c172ea-e48c-4e20-9bee-3470278bd801""
        }]";
    var test2 = JsonConvert.DeserializeObject<DataTable>(jsonString2);
}

Exception:

Newtonsoft.Json.JsonSerializationException HResult=0x80131500 Message=Unexpected JSON token when reading DataTable: EndArray. Path '[0].col2', line 4, position 12. Source=Newtonsoft.Json StackTrace: at Newtonsoft.Json.Converters.DataTableConverter.GetColumnDataType(JsonReader reader) at Newtonsoft.Json.Converters.DataTableConverter.GetColumnDataType(JsonReader reader) at Newtonsoft.Json.Converters.DataTableConverter.CreateRow(JsonReader reader, DataTable dt, JsonSerializer serializer) at Newtonsoft.Json.Converters.DataTableConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, Object existingValue) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent) at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType) at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings) at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings) at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value)

Update 1: @D-Shih I removed the extra comma after col3 to make that "Json Parser" happy but, I still get the same exact Exception. Note that I do not get any error on test1 but I do get the error on test2.

D-Shih D-Shih · Accepted Answer · 2018-07-06T21:48:29

The error from your test JSON data. remove the comma after col3

 ""col3"": ""b2c172ea-e48c-4e20-9bee-3470278bd801""

instead of

 ""col3"": ""b2c172ea-e48c-4e20-9bee-3470278bd801"",

I would recommed a website can easy check JSON format

Json Parser

EDIT

I saw the Json.net source code

If you want to JsonConvert.DeserializeObject as DataTable, you can't give it. an empty array

on source code

private static void CreateRow(JsonReader reader, DataTable dt)

there is a part of code Type columnType = GetColumnDataType(reader); to get json colunm type, if you didn't provide a type Json.net can't judgment type of this array.

So you can give the array as an empty string.

look like this.

var jsonString2 = @"[
{
    ""col1"": ""bd3013bb-39a3-4704-b7c9-803c220f8abe"",
    ""col2"": [""""],
    ""col3"": ""b2c172ea-e48c-4e20-9bee-3470278bd801""
}]";

c# online:https://dotnetfiddle.net/M6A3vE

EDIT1

This is an issue, I report to JSON.Net it will be fix in future version

Fix error when deserializing empty array in DataTable

How to get DataTable from JSON string that contains an empty array using JsonConvert?

1 Answers