Deserialize collection of interface-instances?

I would like to serialize this code via json.net:

public interface ITestInterface
{
    string Guid {get;set;}
}

public class TestClassThatImplementsTestInterface1
{
    public string Guid { get;set; }
}

public class TestClassThatImplementsTestInterface2
{
    public string Guid { get;set; }
}


public class ClassToSerializeViaJson
{
    public ClassToSerializeViaJson()
    {             
         this.CollectionToSerialize = new List<ITestInterface>();
         this.CollectionToSerialize.add( new TestClassThatImplementsTestInterface2() );
         this.CollectionToSerialize.add( new TestClassThatImplementsTestInterface2() );
    }
    List<ITestInterface> CollectionToSerialize { get;set; }
}

I want to serialize/deserialize ClassToSerializeViaJson with json.net. Serialization is working, but deserialization gives me this error:

Newtonsoft.Json.JsonSerializationException: Could not create an instance of type ITestInterface. Type is an interface or abstract class and cannot be instantiated.

So how can I deserialize the List<ITestInterface> collection?

I found this question while trying to do this myself. After I implemented Piotr Stapp's(Garath's) answer, I was struck by how simple it seemed. If I was merely implementing a method that was already being passed the exact Type (as a string) that I wanted to instantiate, why wasn't the library binding it automatically?

I actually found that I didn't need any custom binders, Json.Net was able to do exactly what I needed, provided I told it that was what I was doing.

When serializing:

string serializedJson = JsonConvert.SerializeObject(objectToSerialize, Formatting.Indented, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.Objects,
    TypeNameAssemblyFormat = System.Runtime.Serialization.Formatters.FormatterAssemblyStyle.Simple
});

When de-serializing:

var deserializedObject = JsonConvert.DeserializeObject<ClassToSerializeViaJson>(serializedJson, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.Objects
});

Relevant documentation: Serialization Settings for Json.NET and TypeNameHandling setting

Bellow full working example with what you want to do:

public interface ITestInterface
{
    string Guid { get; set; }
}

public class TestClassThatImplementsTestInterface1 : ITestInterface
{
    public string Guid { get; set; }
    public string Something1 { get; set; }
}

public class TestClassThatImplementsTestInterface2 : ITestInterface
{
    public string Guid { get; set; }
    public string Something2 { get; set; }
}

public class ClassToSerializeViaJson
{
    public ClassToSerializeViaJson()
    {
        this.CollectionToSerialize = new List<ITestInterface>();
    }
    public List<ITestInterface> CollectionToSerialize { get; set; }
}

public class TypeNameSerializationBinder : SerializationBinder
{
    public string TypeFormat { get; private set; }

    public TypeNameSerializationBinder(string typeFormat)
    {
        TypeFormat = typeFormat;
    }

    public override void BindToName(Type serializedType, out string assemblyName, out string typeName)
    {
        assemblyName = null;
        typeName = serializedType.Name;
    }

    public override Type BindToType(string assemblyName, string typeName)
    {
        var resolvedTypeName = string.Format(TypeFormat, typeName);
        return Type.GetType(resolvedTypeName, true);
    }
}

class Program
{
    static void Main()
    {
        var binder = new TypeNameSerializationBinder("ConsoleApplication.{0}, ConsoleApplication");
        var toserialize = new ClassToSerializeViaJson();

        toserialize.CollectionToSerialize.Add(
            new TestClassThatImplementsTestInterface1()
            {
                Guid = Guid.NewGuid().ToString(), Something1 = "Some1"
            });
        toserialize.CollectionToSerialize.Add(
            new TestClassThatImplementsTestInterface2()
            {
                Guid = Guid.NewGuid().ToString(), Something2 = "Some2"
            });

        string json = JsonConvert.SerializeObject(toserialize, Formatting.Indented, 
            new JsonSerializerSettings
            {
                TypeNameHandling = TypeNameHandling.Auto,
                Binder = binder
            });
        var obj = JsonConvert.DeserializeObject<ClassToSerializeViaJson>(json, 
            new JsonSerializerSettings
            {
                TypeNameHandling = TypeNameHandling.Auto,
                Binder = binder 
            });

        Console.ReadLine();
    }
}