Jerreck's comments are great, and I'll just add a slightly different spin on them:
- NET and Visual Studio live in the realm of developers. We use both for our core, cloud-based application, which is deployed in Microsoft Azure. Think: LEFT brain. I've worked with development teams for a long time. It is a rare developer who is also a strong designer. That's not a complaint; just an observation.
- Dreamweaver lives in the realm of the web designer, who needs to manipulate HTML and CSS to achieve the effect they wish. Many of these designers ALSO start their designs in PhotoShop before moving them over to HTML and CSS. Think: RIGHT brain. I've worked with designers of all stripes for a long time as well. It is a rare designer who is also a strong developer. That's not a complaint; just another observation.
The ideal workflow starts with the designer (like the one at your client who needs to use Dreamweaver), who then passes his or her work (along with the HTML and CSS) to the developer, who in our case implements it in .NET -- so this is where Jerreck's comments miss the mark a bit.
While I know nothing of the designer at your client, I can tell you based on my experience very FEW designers ever make the leap to Visual Studio, nor should they. Most will know HTML reasonably well. Some will know CSS -- though too many of them still depend on outdated tables to create their designs. A few can code with JavaScript or PHP -- though many will cut and paste code that will work for them without actually understanding HOW it works.
Now add to this content management. This isn't really for the designer OR the developer; it's for the people who have to maintain the site (who might otherwise design like welders and write code like plumbers; because that is sometimes what they actually do).
The best content management systems are WYSIWYG, and allow the author or editor to easily add or edit content. Most CMS users do not user Dreamweaver OR Visual Studio, and many of them use free (or purchased) templates for their pages (or have a designer and developer build templates).
If your client needs CMS and it must be in .NET, you might check out DNN (formerly known as DotNetNuke). Most CMS also offer a wide range of plugins that can enhance function (such as assuring responsive design, tying in to a shopping cart or providing authentication for users).
I'd say your work ahead is going to be spending some serious time defining requirements.