Well, ActiveX can be used with .NET, the problem with ActiveX was clear when we had constant breakage of the interface. This was the reason why we invested in a socket version of the plugin for IB and why it continues to be a problem for the folks that use MBTrading.
It's no small task (if it were a small task, we'd have tons of providers), so if your programming skills are minimal, I'd caution against it. However, like phg says, it doesn't hurt to ask them. It also doesn't hurt to give it a shot, some of our providers were surprisingly simple, others were surprisingly difficult and we just didn't know until we got to work on them.
35 methods!The Delta APIlooks rather comprehensive. Moreover, it seems the 'bridge' has used it to attach MQL scripts to Delta which in turn attaches to MT4. ActiveX technology is used, though it is not clear whether that is .NET flavor. User programs attach to Delta, not MT4; Delta may not provide all that MT4 provides. That is, the plugin would be specific to Delta.
One possibility is to contact Delta and show them the RightEdge website. They might be interested in helping getting an additional 'feeder framework' (RE) to work with their platform. It is worth asking I would think.