Telerik MVC Grid with Ajax Binding using EntityObjects gets Circular References exception

Question

I have been using Telerik MVC Grid for quite a while now and It is a great control, however, one annoying thing keeps showing up related to using the grid with Ajax Binding to o

Answer 1

I put the new call into my Application_Start for implement the CustomGridActionResultFactory but the create method never called...

Answer 2

Another good pattern is to simply not avoid creating a ViewModel from the Model. It is a good pattern to include a ViewModel. It gives you the opportunity to make last minute UI related tweaks to the model. For example, you can tweak a bool to have an associated string Y or N to help make the UI look nice, or vice versa. Sometimes the ViewModel is exactly like the Model and the code to copy the properties seems unnecessary, but the pattern is a good one and sticking to it is the best practice.

Answer 3

The first solution works with the grid editing mode, but we have the same problem with the load of the grid that already has rows of objects with circular reference, and to resolve this we need to create a new IClientSideObjectWriterFactory and a new IClientSideObjectWriter. This is what I do:

1- Create a new IClientSideObjectWriterFactory:

public class JsonClientSideObjectWriterFactory : IClientSideObjectWriterFactory
{
    public IClientSideObjectWriter Create(string id, string type, TextWriter textWriter)
    {
        return new JsonClientSideObjectWriter(id, type, textWriter);
    }
}

2- Create a new IClientSideObjectWriter, this time I do not implement the interface, I've inherited the ClientSideObjectWriter and overrided the AppendObject and AppendCollection methods:

public class JsonClientSideObjectWriter : ClientSideObjectWriter
{
    public JsonClientSideObjectWriter(string id, string type, TextWriter textWriter)
        : base(id, type, textWriter)
    {
    }

    public override IClientSideObjectWriter AppendObject(string name, object value)
    {
        Guard.IsNotNullOrEmpty(name, "name");

        var data = JsonConvert.SerializeObject(value,
            Formatting.None,
            new JsonSerializerSettings
                {
                    NullValueHandling = NullValueHandling.Ignore,
                    ContractResolver = new PropertyNameIgnoreContractResolver()
                });

        return Append("{0}:{1}".FormatWith(name, data));
    }

    public override IClientSideObjectWriter AppendCollection(string name, System.Collections.IEnumerable value)
    {
    public override IClientSideObjectWriter AppendCollection(string name, System.Collections.IEnumerable value)
    {
        Guard.IsNotNullOrEmpty(name, "name");

        var data = JsonConvert.SerializeObject(value,
            Formatting.Indented,
            new JsonSerializerSettings
                {
                    NullValueHandling = NullValueHandling.Ignore,
                    ContractResolver = new PropertyNameIgnoreContractResolver()
                });

        data = data.Replace("<", @"\u003c").Replace(">", @"\u003e");

        return Append("{0}:{1}".FormatWith((object)name, (object)data));
    }
}

NOTE: The replace its because the grid renders html tags for the client template in edit mode and if we don't encode then the browser will render the tags. I didn't find a workarround yet if not using a Replace from string object.

3- On my Application_Start on Global.asax.cs I registered my new factory like this:

DI.Current.Register<IClientSideObjectWriterFactory>(() => new JsonClientSideObjectWriterFactory());

And it worked for all components that Telerik has. The only thing that I do not changed was the PropertyNameIgnoreContractResolver that was the same for the EntityFramework classes.

Answer 4

I have taken a slightly different approach which I believe might be a little easier to implement.

All I do is apply an extended [Grid] attribute to the grid json returning method instead of the normal [GridAction] attribute

public class GridAttribute : GridActionAttribute, IActionFilter
  {    
    /// <summary>
    /// Determines the depth that the serializer will traverse
    /// </summary>
    public int SerializationDepth { get; set; } 

    /// <summary>
    /// Initializes a new instance of the <see cref="GridActionAttribute"/> class.
    /// </summary>
    public GridAttribute()
      : base()
    {
      ActionParameterName = "command";
      SerializationDepth = 1;
    }

    protected override ActionResult CreateActionResult(object model)
    {    
      return new EFJsonResult
      {
       Data = model,
       JsonRequestBehavior = JsonRequestBehavior.AllowGet,
       MaxSerializationDepth = SerializationDepth
      };
    }
}

and

public class EFJsonResult : JsonResult
  {
    const string JsonRequest_GetNotAllowed = "This request has been blocked because sensitive information could be disclosed to third party web sites when this is used in a GET request. To allow GET requests, set JsonRequestBehavior to AllowGet.";

    public EFJsonResult()
    {
      MaxJsonLength = 1024000000;
      RecursionLimit = 10;
      MaxSerializationDepth = 1;
    }

    public int MaxJsonLength { get; set; }
    public int RecursionLimit { get; set; }
    public int MaxSerializationDepth { get; set; }

    public override void ExecuteResult(ControllerContext context)
    {
      if (context == null)
      {
        throw new ArgumentNullException("context");
      }

      if (JsonRequestBehavior == JsonRequestBehavior.DenyGet &&
          String.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
      {
        throw new InvalidOperationException(JsonRequest_GetNotAllowed);
      }

      var response = context.HttpContext.Response;

      if (!String.IsNullOrEmpty(ContentType))
      {
        response.ContentType = ContentType;
      }
      else
      {
        response.ContentType = "application/json";
      }

      if (ContentEncoding != null)
      {
        response.ContentEncoding = ContentEncoding;
      }

      if (Data != null)
      {
        var serializer = new JavaScriptSerializer
        {
          MaxJsonLength = MaxJsonLength,
          RecursionLimit = RecursionLimit
        };

        serializer.RegisterConverters(new List<JavaScriptConverter> { new EFJsonConverter(MaxSerializationDepth) });

        response.Write(serializer.Serialize(Data));
      }
    }

Combine this with my serializer Serializing Entity Framework problems and you have a simple way of avoiding circular references but also optionally serializing multiple levels (which I need)

Note: Telerik added this virtual CreateActionResult very recently for me so you may have to download the latest version (not sure but I think maybe 1.3+)