What do I need to create a WebDAV Server?

Question

I started with an ASP.NET MVC 2 solution and ended up pretty well.

I can subscribe an .ics file and push new events and changes to my CRM Diary as every change made remotely fires a PUT Method with the entire calendar as an inputStream.

this works fine with Thunderbird w/Lightning, but it becomes a ReadOnly Calendar in all the other used Calendar applications

And everywhere I search, it mentions that only WebDAV Server can have Read/Write permissions.

What can I do?

My idea started to be able to use a Calendar Client Software in any device or computer to use the CRM Diary (so we don't actual need to work in it).