Can I use polymorphism/inheritance in C# DocumentDb driver

Question

I have a custom form object structure I use successfully with mongodb.

I've been investigating the possibility of replacing Mongo with DocumentDb.

My Class structure consists of a base control that different types of control inherit from. e.g. Textbox control, Dropdown Control

In mongo I use the discriminator field to store the actual type, in the c# DocumentDb driver I cant see find the same feature.

below is a sample of how mongo stores my class structure.

{
  "_t" : "TextboxControl",
  "LabelText" : "Location of incident",
  "IsRequired" : true,
  "_id" : "cbe059d9-b6a9-4de2-b63b-14d44b022e37"
}

In documentdb the structure looks like

{
  "LabelText": "Location of incident",
  "IsRequired": true,
  "id": "cbe059d9-b6a9-4de2-b63b-14d44b022e37"
}

As you can see the mongo version has a "_t" property stating the actual type, this is then used when I read the data to create the correct type. In the documentdb version it is simply a fieldtype

Answer 1

After many weeks of searching I eventually came across the answer

https://github.com/markrexwinkel/azure-docdb-linq-extension

Basically this library extends the DocumentDb's C# SDK and allows for custom JSON settings to be applied. Under the hood the documentdb driver users json.net.

I now get the property "$type" which is a feature built into newtonsoft's excellent json.net library.

My json now looks like

{
  "$type" : "MyNameSpace.DropDownSingleFormBuilderControlTemplate, MyLibrary",
  "LabelText" : "Label Text"
  "IsRequired" : true,
  "_id" : "cbe059d9-b6a9-4de2-b63b-14d44b022e37"
}

Answer 2

I think they added support for jsonserializer. You can add it via the
RequestOptions, TypeNameHandling.All

var s =  new RequestOptions(){ JsonSerializerSettings = new JsonSerializerSettings() { TypeNameHandling = TypeNameHandling.All }}
var result = await Client.CreateDocumentAsync(CollectionUri, @event2, s);