Deserialize json with auto-trimming strings

Question

I use Newtonsoft.Json library

Is there a way to trim spaces from any string data during deserialization?

class Program
{
    class Person
    {
              


        

Answer 1

You could write your own JsonConverter:

public class TrimmingConverter : JsonConverter
{
    public override bool CanRead => true;
    public override bool CanWrite => false;

    public override bool CanConvert(Type objectType) => objectType == typeof(string);

    public override object ReadJson(JsonReader reader, Type objectType,
                                    object existingValue, JsonSerializer serializer)
    {
        return ((string)reader.Value)?.Trim();
    }

    public override void WriteJson(JsonWriter writer, object value, 
                                   JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

You can use it like this to apply to all string fields:

var json = @"{ name:"" John "" }"
var p = JsonConvert.DeserializeObject(json, new TrimmingConverter());
Console.WriteLine("Name is: \"{0}\"", p.Name);
//Name is: "John"

Or you can apply this to certain fields only:

public class Person
{
    [JsonProperty("name")]
    [JsonConverter(typeof(TrimmingConverter))] // <-- that's the important line
    public string Name { get; set; }
    [JsonProperty("other")]
    public string Other { get; set; }
}

var json = @"{ name:"" John "", other:"" blah blah blah "" }"
var p = JsonConvert.DeserializeObject(json);
Console.WriteLine("Name is: \"{0}\"", p.Name);
Console.WriteLine("Other is: \"{0}\"", p.Other);

//Name is: "John"
//Other is: " blah blah blah "