Get All 'documents' from MongoDB 'collection'

Using the current version of the driver (v2.0) you can do that by passing a filter that matches everything:

var documents = await SpeCollection.Find(_ => true).ToListAsync();

They have also added an empty filter (FilterDefinition.Empty) which will arrive in the next version of the driver (v2.1):

var documents = await SpeCollection.Find(Builders<Project>.Filter.Empty).ToListAsync();

Simplest Way

Retrieve all the documents-

var documents = SpeCollection.AsQueryable();

Also convert to JSON object-

var json = Json(documents, JsonRequestBehavior.AllowGet);