How to ignore property conditionally during JSON serialization

Consider i have class Employer, i want serialize this class to json string and need ignore some properties conditionally. For ex: in my example, i want to include address1 and address2 only if it has valid values

  public class Employer

    {

 public int id { get; set; }

        public string name { get; set; }

       

 public string ssn { get; set; }

        public string address1 { get; set; }

        public string address2 { get; set; }

   }

Declare some values

Employer employer = new Employer(){ … address1 = "some value", address2 = null };

Now serialize it for json string

var jsonstring = JsonConvert.SerializeObject(employer,

                       Newtonsoft.Json.Formatting.None,

                       new JsonSerializerSettings

                       {

                           

                       });

Here you will get all the properties.

Now lets see how to ignore the properties conditionally, you can choose either one of these options.

Option 1: Use ShouldSerialize property inside class itself like below. But you need add individual shouldSerialize property for each class property.

  public class Employer

    {

 public int id { get; set; }

        public string name { get; set; }

       

 public string ssn { get; set; }

        public string address1 { get; set; }

        public string address2 { get; set; }

        public bool ShouldSerializeaddress1()

        {

            // don't serialize if it is null or empty or add any your custom conditions

            return !string.IsNullOrEmpty(address1);

        }

        public bool ShouldSerializeaddress2()

        {

            // don't serialize if it is null or empty or add any your custom conditions

            return !string.IsNullOrEmpty(address2);

        }

   }

Option 2: Instead creating multiple ShouldSerialize property inside class, we can create ContractResolver and add it in Json serialization as below,

Create Resolver Class,

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

  public class EmployerShouldSerializeContractResolver : DefaultContractResolver

    {

        public new static readonly EmployerShouldSerializeContractResolver Instance = new EmployerShouldSerializeContractResolver();

        protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)

        {

            JsonProperty property = base.CreateProperty(member, memberSerialization);

            if (property.DeclaringType == typeof(Employer))

            {

                property.ShouldSerialize =

                    instance =>

                    {

                        //ignore default values

                        return instance.GetType().GetProperty(member.Name).GetValue(instance, null) != property.DefaultValue;

                    };

            }

            return property;

        }

    }

Include it in JSON serialization,

var jsonstring = JsonConvert.SerializeObject(employer,

                       Newtonsoft.Json.Formatting.None,

                       new JsonSerializerSettings

                       {

                           ContractResolver = new EmployerShouldSerializeContractResolver()

                       });

MVC & WebAPI - Model Binder

There are some specific cases in order to use model binder to MVC and WebAPI in same project.

Here i will explain step by step to implement MVC and WebAPI Model Binders

What is Model Binder?

In some cases, we should do common operations for all actions inside controller. So in that case we can add model binder and pass as parameter to actions. In below example UserModel class sent as Model Binder

public ActionResult Index([ModelBinder]UserModel model)

{

...

}

Implementing Model Binder for MVC

MVC uses different namespace such as System.Web.Mvc. So Model Binder class also should use the same.

Step 1:

Create UserModel class as required. Here we can add our required properties. In this example, i am going to display UserId and UserName

public class UserModel

    {

        public string UserId { get; set; }

        public string UserName { get; set; }

    }

Step 2:

Create custom ModelBinder class which can be implemented from System.Web.Mvc.IModelBinder as below. Here i created as partial for merging with WebAPI. If you dont need WebAPI then just have it as normal class

public partial class UserModelBinder : System.Web.Mvc.IModelBinder

    {

        public object BindModel(System.Web.Mvc.ControllerContext controllerContext, System.Web.Mvc.ModelBindingContext bindingContext)

        {

            if (bindingContext.ModelType != typeof(UserModel))

            {

                return null;

            }

            UserModel userModel = new UserModel();

            var userId = HttpContext.Current.User.Identity.GetUserId();

            if (!string.IsNullOrEmpty(userId))

            {

/// Create your custom logics to fill the other required details. In this example i can fill username

            }

            return userModel;

        }

    }

Step 3:

Register this Custom ModelBinder class into Global.asax.cs file

protected void Application_Start()

        {

            AreaRegistration.RegisterAllAreas();

            WebApiConfig.Register(GlobalConfiguration.Configuration);

            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);

            RouteConfig.RegisterRoutes(RouteTable.Routes);

            BundleConfig.RegisterBundles(BundleTable.Bundles);

            //Model binder for MVC controller usermodel

            ModelBinders.Binders.Add(typeof(UserModel), new UserModelBinder());

        }

Step 4:

Use this custom model binder in action methods of MVC controller

public ActionResult Index([System.Web.Http.ModelBinding.ModelBinder]UserModel model)

{

...

 //Write your logic to do with UserModel class object

}

Thats all for MVC Model Binder.

Implementing Model Binder for WebAPI

WebAPI cannot be worked with MVC model binder. So we need to create differently. Step 1 to create UserModel is same. So i will go from Step 2

Step 2:

Create Custom Model Binder for WebAPI as follows. Here IModelBinder uses System.Web.Http.ModelBinding.

using Microsoft.AspNet.Identity;

using System.Web;

using System.Web.Http;

using System.Web.Http.ModelBinding;

public partial class UserModelBinder : IModelBinder

    {

        public bool BindModel(System.Web.Http.Controllers.HttpActionContext actionContext, ModelBindingContext bindingContext)

        {

            if (bindingContext.ModelType != typeof(UserModel))

            {

                return false;

            }

            UserModel userModel = new UserModel();

            var userId = HttpContext.Current.User.Identity.GetUserId();

            if (!string.IsNullOrEmpty(userId))

            {

               //Your logic to fill usermodel class and assign to binding context’s model

                bindingContext.Model = userModel;

                return true;

            }

            bindingContext.ModelState.AddModelError(bindingContext.ModelName, "Error in model binding");

            return false;

        }

    }

Step 3:

Create ModelBinderProvider class as follows. It is going to be register with configuration. Here ModelBinderProvider uses namespace System.Web.Http.ModelBinding..

public class UserModelBinderProvider : ModelBinderProvider

    {

        private System.Type type;

        private UserModelBinder userModelBinder;

        public UserModelBinderProvider(System.Type type, UserModelBinder userModelBinder)

        {

            this.type = type;

            this.userModelBinder = userModelBinder;

        }

        public override IModelBinder GetBinder(HttpConfiguration configuration, System.Type modelType)

        {

            if (modelType == type)

            {

                return userModelBinder;

            }

            return null;

        }

    }

Step 4:

Register ModelBinderProvider in Global.asax.cs file under WebApiConfig register method

public static class WebApiConfig

    {

    public static void Register(HttpConfiguration config)

        {

         var provider = new UserModelBinderProvider(typeof(UserModel), new UserModelBinder());

         config.Services.Insert(typeof(ModelBinderProvider), 0, provider);

Step 5:

Use in APIController action methods as follows

[HttpGet]

        public string GetUserName([ModelBinder]UserModel model)

        {

              return model.UserName;

  }

Thats all for WebAPI Model Binder.

MVC - 401 Unauthorization redirect page

Sometimes we need to redirect our pages to some specific path when 401 unauthorized error happen. But by default it will redirect to some predefined path (Ex: ../login.aspx?ReturnUrl=home/index) and it may go 404 error if not found in our project.

To customize this default redirect path, i went through many ways and finally found simple change is

<authentication mode="Forms">

      <forms timeout="60" loginUrl="~/" />

</authentication>

Note: In browser network tab we cannot see 401 (Unauthorized) error, it will show as 302 (Redirect found). To resolve this, we can customize application end request method in global.asax file like below, But it will not redirect to login page instead it will show error page.

void Application_EndRequest(object sender, EventArgs e)

{

    if (Context.Response.StatusCode == 302)

    {

        Context.Response.Clear();

        Context.Response.StatusCode = 401;

    }

}