json-serialization-9.cs

internal class MyApiPostedValuesConverter : JsonConverter<IDictionary<string, IList<string>>>
{
    public override bool CanConvert(Type typeToConvert) => true;

    public override IDictionary<string, IList<string>> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        if (reader.TokenType != JsonTokenType.StartObject)
        {
            throw new JsonException(GetJsonExceptionMessage("Start object token not found"));
        }

        var result = new Dictionary<string, IList<string>>();
        while (reader.Read())
        {
            if (reader.TokenType == JsonTokenType.EndObject)
            {
                return result;
            }

            if (reader.TokenType != JsonTokenType.PropertyName)
            {
                throw new JsonException(GetJsonExceptionMessage("Field alias token not found"));
            }

            string fieldAlias = GetFieldAlias(ref reader);

            reader.Read();

            result[fieldAlias] = GetFieldValues(ref reader);
        }

        throw new JsonException(GetJsonExceptionMessage("End object token not found"));

        static string GetJsonExceptionMessage(string message) => $"Could not read input in {nameof(UmbracoFormsApiPostedValuesConverter)}. {message}.";

        static string GetFieldAlias(ref Utf8JsonReader reader)
        {
            string? fieldAlias = reader.GetString();
            if (string.IsNullOrEmpty(fieldAlias))
            {
                throw new JsonException(GetJsonExceptionMessage("Field alias value is empty"));
            }

            return fieldAlias;
        }

        static List<string> GetFieldValues(ref Utf8JsonReader reader)
        {
            var fieldValues = new List<string>();
            if (reader.TokenType == JsonTokenType.String)
            {
                string fieldValue = reader.GetString() ?? string.Empty;
                fieldValues.Add(fieldValue);
            }
            else if (reader.TokenType == JsonTokenType.StartArray)
            {
                fieldValues = new List<string>();
                while (reader.TokenType != JsonTokenType.EndArray)
                {
                    if (reader.TokenType == JsonTokenType.String)
                    {
                        string fieldValue = reader.GetString() ?? string.Empty;
                        fieldValues.Add(fieldValue);
                    }

                    reader.Read();
                }
            }

            return fieldValues;
        }
    }

    public override void Write(Utf8JsonWriter writer, IDictionary<string, IList<string>> value, JsonSerializerOptions options) => throw new NotImplementedException();
}