Missing LINQ to SQL Classes (DBML designer) in Visual Studio 2017 RC

You need to opt in to enable the designer during installation, it is not enabled by default: https://developercommunity.visualstudio.com/content/problem/4616/linq-to-sql-dbml-designer-in-not-working.html

"Editing .dbml files with a designer surface requires the LINQ to SQL tools which are not installed by default as part of any of the workloads of Visual Studio 2017. It can be installed by selecting the 'LINQ to SQL tools' item under the 'Code Tools' category in the 'Individual Components' tab of the Visual Studio installer."

By default VS 2017 installer doesn't provide LINQ to SQL tools while installing we have to select that and modify.

Follow easy steps from here:

Open VS2017 installer.

Go to Individual Components.

Select he LINQ To SQL tools from code tools.

and just modify.

or check this screenshot you will get the idea.