Automatically HtmlEncode strings when model is serialized with Json.Net

You can use a solution similar to the solution to selectively remove HTML in lines during deserialization , with a few minor changes:

• Change HtmlEncodingValueProvider
  
  to apply encoding in GetValue
  
  , not SetValue
  
  (so that it encodes serialization, not deserialization).
• Modify the transformer to apply the value provider to all row properties, rather than look up the attribute.

This is what the resulting code would look like:

public class CustomResolver : DefaultContractResolver
{
    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        IList<JsonProperty> props = base.CreateProperties(type, memberSerialization);

        // Attach an HtmlEncodingValueProvider instance to all string properties
        foreach (JsonProperty prop in props.Where(p => p.PropertyType == typeof(string)))
        {
            PropertyInfo pi = type.GetProperty(prop.UnderlyingName);
            if (pi != null)
            {
                prop.ValueProvider = new HtmlEncodingValueProvider(pi);
            }
        }

        return props;
    }

    protected class HtmlEncodingValueProvider : IValueProvider
    {
        PropertyInfo targetProperty;

        public HtmlEncodingValueProvider(PropertyInfo targetProperty)
        {
            this.targetProperty = targetProperty;
        }

        // SetValue gets called by Json.Net during deserialization.
        // The value parameter has the original value read from the JSON;
        // target is the object on which to set the value.
        public void SetValue(object target, object value)
        {
            targetProperty.SetValue(target, (string)value);
        }

        // GetValue is called by Json.Net during serialization.
        // The target parameter has the object from which to read the string;
        // the return value is the string that gets written to the JSON
        public object GetValue(object target)
        {
            string value = (string)targetProperty.GetValue(target);
            return System.Web.HttpUtility.HtmlEncode(value);
        }
    }
}

      

        
        
        
      

    

Use custom ContractResolver

like this:

var settings = new JsonSerializerSettings
{
    ContractResolver = new CustomResolver(),
    Formatting = Formatting.Indented
};

string json = JsonConvert.SerializeObject(your_object, settings);

      

        
        
        
      

    

Fiddle: https://dotnetfiddle.net/RhFlk8