CensoredContentAttribute

CensoredContentAttribute.cs

using System;
using System.Reflection;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

namespace Logging
{
  public abstract class CensoredContentAttribute : Attribute
  {
    public abstract string Censor { get; }

    public abstract string TruncateData(string input);
  }

  public class CensoredContentContractResolver<T> : DefaultContractResolver where T : CensoredContentAttribute
  {
    protected override IValueProvider CreateMemberValueProvider(MemberInfo member)
    {
      if (member.IsDefined(typeof(T)))
      {
        var attr = (T)Attribute.GetCustomAttribute(member, typeof(T));
        return new CensorContentValueProvider(base.CreateMemberValueProvider(member), attr);
      }
      else
      {
        return base.CreateMemberValueProvider(member);
      }
    }

    class CensorContentValueProvider : IValueProvider
    {
      private readonly IValueProvider _inner;
      private readonly CensoredContentAttribute _censorAttr;
      public CensorContentValueProvider(IValueProvider inner, CensoredContentAttribute censorAttr)
      {
        _censorAttr = censorAttr;
        _inner = inner; 
      }
      public object GetValue(object target)
      {
        var targetString = _inner.GetValue(target)?.ToString() ?? string.Empty;

        return _censorAttr.TruncateData(targetString);
      }
      public void SetValue(object target, object value)
      {
        _inner.SetValue(target, value);
      }
    }
  }
  public class CensoredJsonSerializerSettings<T> : JsonSerializerSettings where T : CensoredContentAttribute
  {

    public CensoredJsonSerializerSettings()
    {
      ContractResolver = new CensoredContentContractResolver<T>();
    }
  }
}

Example.cs

using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

namespace Logging
{
  public class LoggingExample 
  {
    
    [Redacted(ShowFirst:3, ShowLast:3)]
    public string Name {get; set;} = "Richard Johnson"
    
    public string ToSerializedString() {
      return JsonConvert.SerializeObject(this, new CensoredJsonSerializerSettings<RedactedAttribute>());
      // Returns "Ric***REDACTED***son"
    }
  }
}

LargeDataAttribute.cs

namespace Logging
{
  public class LargeDataAttribute : CensoredContentAttribute
  {
    public override string Censor { get => "***Large Data Removed***"; }

    public int Threshold { get; set; }

    public override string TruncateData(string input) 
    {
      var byteLength = input?.Length ?? 0;

      if (byteLength > Threshold)
      {
        return $"{Censor} [Length: {byteLength}]";
      }
      else
      {
        return input;
      }
    }
  }
}

RedactedAttribute.cs

namespace Logging
{
  public class RedactedAttribute : CensoredContentAttribute
  {
    /*
     * https://piwik.pro/blog/what-is-pii-personal-data/
     * Full name
     * Home address
     * Email address
     * Social security number
     * Passport number
     * Driver’s license number
     * Credit card numbers
     * Date of birth
     * Telephone number
     * Log in details
    */
    public override string Censor { get => "***REDACTED***"; }
    public int ShowFirst { get; set; }
    public int ShowLast { get; set; }

    public override string TruncateData(string input)
    {
      var output = string.Empty;
      if (ShowFirst + ShowLast >= input.Length)
      {
        return Censor;
      }

      if (ShowFirst > 0)
      {
        output += input?.Substring(0, ShowFirst > input.Length ? input.Length : ShowFirst) ?? string.Empty;
      }

      output += Censor;

      if (ShowLast > 0)
      {
        output += input?.Substring(ShowLast > input.Length ? 0 : input.Length - ShowLast, ShowLast > input.Length ? input.Length : ShowLast) ?? string.Empty;
      }

      return output.Length > 0 ? output : Censor;
    }
  }
}