Cannot deserialize the current JSON array for Revit design automation workitem

Question

1. i have a json file like below as input parameters for Revit design automation:

const data = {
    ModelId: "dXJuOmFkc2sud2lwcHJvZDpmcy5maWxlOnZmLjNSTzhMWmtUVGVHM3p1M1FoNjRGM3c_dmVyc2lvbj0x",
    ElementIds: [{
        "UniqueId": "ca5762b5-0f46-4a2f-8599-1d1a5dd19a81-00024b8c"
    }, {
        "UniqueId": "91e18c07-1bae-4949-a093-e0a4552bb478-000241ea"
    }]
};
var file = new File([data], "inputParameters.json", {
    type: "application/json"
});

2. "success" workitem except the below error message in report file:

[07/09/2022 03:36:41] Exception when parsing json file: Newtonsoft.Json.JsonSerializationException: Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'ProjectSchedule.InputCache' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.

3. my Revit plugin C# code as below:

    public static bool ImportFromCache(Application rvtApp, Document doc)
    {
        InputCache inputCache = InputCache.Parse("inputParameters.json");
    }
    internal class InputCache
    {
        public string ModelId { get; set; } = "";
        public string[] ElementIds { get; set; } = { };
        static public InputCache Parse(string jsonPath)
        {
            if (!File.Exists(jsonPath)) return new InputCache { ModelId = "", ElementIds = { } };
            string jsonContents = File.ReadAllText(jsonPath);
            return JsonConvert.DeserializeObject<InputCache>(jsonContents);
        }
    }

4. i tried to fix it via below C# code:

    public static bool ImportFromCache(Application rvtApp, Document doc)
    {
        string jsonContents = File.ReadAllText("cache.json");
        var inputCache = JsonConvert.DeserializeObject<List<InputCache>>(jsonContents);
    }
    internal class InputCache
    {
        public string ModelId { get; set; } = "";
        public string[] ElementIds { get; set; } = { };
    }

5. but "failedInstructions" workitem w/ below error message in report file:

[07/09/2022 05:02:16] Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: o. Path '', line 1, position 1.

Answer 1

There are 2 problems with your example.

First: You are saving the json data as an array but trying to deserialize as an object:

var file = new File([data], "inputParameters.json", {
    type: "application/json"
});

This explains the error you have:

Exception when parsing json file: Newtonsoft.Json.JsonSerializationException: Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'ProjectSchedule.InputCache' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.

To fix this, you can change your js code to not convert your data into an array or account for an array in your appbundle code.

A possible solution in js code:

var file = new File([JSON.stringify(data)], "inputParameters.json", {
    type: "text/plain"
});

Or change in appbundle code (removes the redundant square brackets):

string fileContents = File.ReadAllText("cache.json");
string jsonContents = fileContents.Substring(1, fileContents.Length-2);
var inputCache = JsonConvert.DeserializeObject<List<InputCache>>(jsonContents);

The second problem that you have not yet encountered with deserialization is explained in an earlier answer.

Answer 2

Your JSON data and the class object you are trying to deserialize to do not match. Your JSON data has a list of objects (ElementId) with each element id containing a field UniqueId. Where as your class InputCache expects only an array of strings. The fix would be to either change your json data format or the InputCache class structure.

Here is an example on .NET fiddle: https://dotnetfiddle.net/RfX20L

using System;
using Newtonsoft.Json;

public class Program
{
    internal class ElementId
    {
      public string UniqueId { get; set; }
    }

    internal class InputCache
    {
      public string ModelId { get; set; }
      public ElementId[] ElementIds { get; set; }
    }
    
    public static void Main()
    {
        var json = "{'ModelId':'dXJuOmFkc2sud2lwcHJvZDpmcy5maWxlOnZmLjNSTzhMWmtUVGVHM3p1M1FoNjRGM3c_dmVyc2lvbj0x','ElementIds':[{'UniqueId':'ca5762b5-0f46-4a2f-8599-1d1a5dd19a81-00024b8c'},{'UniqueId':'91e18c07-1bae-4949-a093-e0a4552bb478-000241ea'}]}";
        
        var obj = JsonConvert.DeserializeObject<InputCache>(json);
        
        foreach(var id in obj.ElementIds) {
            Console.WriteLine(id.UniqueId);
        }
        
    }
}