如何在linq查询中反序列化json对象？

Question

I am fetching json data from txt file in linq and performing some actions on that to making the process fast. but when I am trying to call that query then it's showing me an error for deserialization of json object. So how to deserialize it?

I am getting error like

Cannot deserialize the current JSON object (eg {"name":"value"}) into type 'System.Collections.Generic.List1[MMF.LiveAMData]' because the type requires a JSON array (eg [1,2,3]) to deserialize correctly.

I search to solve this issue but almost all answers performing desrialization without linq. I need to use linq due to time latency.

Below is my method which I am calling

public static void something()
      {
          File.ReadLines(filePath)
              .AsParallel()
              .Select(x => x.TrimStart('[').TrimEnd(']'))
              .Select(JsonConvert.DeserializeObject<List<LiveAMData>>)
              .ForAll(WriteRecord);
      }

and below is my class object which I am using

public class LiveAMData
    {
        public string ev { get; set; }
        public string sym { get; set; }
    }

Answer 1

You're trying to deserialize a JSON array, but you're trimming the [ and ] parts so that it's no longer a JSON array. Remove the trim line:

public static void something()
{
    File.ReadLines(filePath)
        .AsParallel()
        .Select(JsonConvert.DeserializeObject<List<LiveAMData>>)
        .ForAll(WriteRecord);
}

If each line of your file is a JSON array like so:

[{"ev":"Test1", "sym": "test"},{"ev":"Test2", "sym": "test"}]

Your trim line will change it to this invalid JSON:

{"ev":"Test1", "sym": "test"},{"ev":"Test2", "sym": "test"}

Which certainly can't be deserialized to a List<LiveAMData>>

Answer 2

As you are deserializing each object individually, you don't need the List type in the DeserializeObject call. Try this:

        public static void something()
        {
            File.ReadLines(filePath)
                .AsParallel()
                .Select(x => x.TrimStart('[').TrimEnd(']'))
                .Select(JsonConvert.DeserializeObject<LiveAMData>)
                .ForAll(WriteRecord);
        }