When you open a project or solution in Microsoft Visual Studio, the code editor and Windows Form Designer windows are opened in the same state they were in when the project was last saved. Once a project or solution is opened, use the Solution Explorer to navigate between the files of the opened project or solution.
To open an existing project or solution file
The Open Project/Solution dialog box will allow you to open a wide range of project files which include projects, Microsoft Visual Studio .NET solutions, and Microsoft Visual C++ projects. Use the Objects of Type drop-down list to control which type of projects or solutions you see in the file selection area of the Open Project dialog box.
For information on migrating from VBA to .NET, see https://adndevblog.typepad.com/autocad/devtv/. Search for 'API webcast archive' and click the link 'AutoCAD: VBA to .NET Migration' to download a video on migrating VBA code to .NET.