Custom JSON Serializer for the Entity Framework

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Introduction

Entity Framework’s entity (which has a relationship with other entities) cannot serialize with .NET Framework’s existing object like JavascriptSerializer or DataContract JSON Serializer or JsonResult. So I needed to solve that problem by myself.

Background

In one of our projects, we used ASP.NET MVC for presentation/business logic layer and Entity framework for data access layer. At that time I faced the problem. I needed to call server side methods from client side JavaScript with the help of XMLHttp request. In the client side, we used JQuery (JavaScript library). The server side methods needed to return data with Jason format. At first I tried to use JsonResult (MVC framework) to transform that data to JSON format, then one error message was thrown. The error message was “Circular Reference error”. Then I used JavascriptSerializer class. But the same thing occurred. Then I tried DataContract JSON Serializer. I got the same error once again.

I was wondering what I should do. I first started Googling to solve my problem. There I found that Entity framework’s Entity serialization had some problem with the existing JSON Serializer provided by the .NET Framework. So, I started thinking of writing my own small serializer to solve and use Entity framework with JSON.

Solution

public class CustomJSonSerializer
{

public static string JsonSerialize<T>(T obj) where T : class
{
    var sb = new StringBuilder("{");

    var parentType = obj.GetType(); // I get type from given object 

    // use reflection to retrieve all properties of that type
    var ms = parentType.GetMembers().Where(v => v.MemberType 
        == MemberTypes.Property).ToList<MemberInfo>();

    const string doubleQuote = "\"";
    var counter = 0;
    var stringTypes = new List<String> { "String", "Guid", 
        "Boolean" };

    //Following Types are used by Entity Framework. So no need to 
    //serialize those types.
    var ignoreEntityTypes = new List<String> { "EntityReference`1", 
        "EntityCollection`1", "EntityState", 
        "EntityKey", "EntitySetName" };

    //Start iteration to navigate each property
    foreach (PropertyInfo p in ms)
    {
        counter++;
        var propertyName = p.Name;
        var propertyType = p.PropertyType;
        var propertyValue = p.GetValue(obj, null);

        //If property type is matched with ignoreTypes then
        //goto next loop
        if (ignoreEntityTypes.Contains(propertyType.Name))
        {
            continue;
        }

        if (stringTypes.Contains(propertyType.Name))
        {
            if (propertyValue == null)
            {
                sb.Append(doubleQuote + propertyName + doubleQuote + 
                          ":" + "null");
            }

            else
            {
                sb.Append(doubleQuote + propertyName + doubleQuote + 
                    ":" + doubleQuote + propertyValue.ToString() + doubleQuote);
            }
        }

        else if (propertyType != null && propertyType.IsPrimitive)
        {
            sb.Append(doubleQuote + propertyName + doubleQuote 
                + ":" + propertyValue.ToString());
        }

        //Still I have doubt how Date Time will be handled.
        else if (propertyType.Name == "DateTime")
        {
            var dt = (DateTime)propertyValue;
            sb.Append(doubleQuote + propertyName 
                + doubleQuote + ":" 
                + "new Date(" + dt.Ticks.ToString() + ")");
        }
        else
        {
            if (propertyValue != null)
            {
                sb.Append(doubleQuote + propertyType.Name + doubleQuote + ":");
                //If property value is another entity, then
                //call the method recursively.
                sb.Append(JsonSerialize(propertyValue));
            }
            else
            {
                continue;
            }
        }
        //If it is not the last property, then add comma
        if (counter < ms.Count)
        {
            sb.Append(",");
        }
    }
    sb.Append("}");
    var result = sb.ToString().Replace(",}", "}");
    return result;
}

Limitation

I did not test it with very complex scenarios. So issues may arise. Still, I do not know how the JSON Serializer handles datetime. I use the Tick property of the DateTime method. It may be incorrect.

Conclusion

I solved my problem in this way. I hope it will work for you if you need to work with Entity framework and JSON format.

History

• 29^th April, 2009: Initial post