https://stackoverflow.com/questions/44115979/newtonsoft-json-automatically-encode-strings-when-the-model-is-serialized

CSharp · Console

/Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
					
public class Program
{
	public static void Main()
	{
		Foo foo = new Foo
		{
			Name = "<b>Foo Bar</b>",
			Description = @"<p class=""intro"">Bada Boom Bada Bing</p>"
		};
		
		var settings = new JsonSerializerSettings
		{
			ContractResolver = new CustomResolver(),
			Formatting = Formatting.Indented
		};
		
		string json = JsonConvert.SerializeObject(foo, settings);
		Console.WriteLine(json);
	}
}


class Foo
{
	public string Name { get; set; }
	public string Description { get; set; }
}


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 HttpUtility.HtmlEncode(value);
		}
	}
}



// Note: Following is a stand-in for the System.Web.HttpUtility class,
// as dotnetfiddle apparently does not provide access to the System.Web namespace.
// In your production code, please use the real version provided by .NET; do NOT use this stand-in class.
public static class HttpUtility
{
    public static string HtmlEncode(string s)
	{
		if (s != null)
		{
			// \u0026 is an ampersand; needed here to get around a dotnetfiddle bug
			s = s.Replace("\u0026", "\u0026amp;")
				 .Replace("<", "\u0026lt;")
				 .Replace(">", "\u0026gt;")
				 .Replace("\"", "\u0026quot;");
		}
		return s;
	}
}