Design Time - It takes too long to save changes if the Design View is / was opened

You may have noticed that the overall Designer performance was increased in the latest releases.
Previously, when you saved changes on a page where the Designer was opened at least once, Visual Studio became unresponsive for seconds. We fixed this issue in v20.1.

While working on it, we found that performance is also affected in another case - when a page's Designer is opened for the first time. We made multiple attempts to eliminate this issue, but it is affected by many factors:

• your application is a WebSite instead of WebProject;
• you have many Master pages;
• your page's layout is complex;
• the designer is opened for the first time, which forces generation of license files (the App_License.dll and licenses.licx files);

Although we slightly improved performance for the last case, we couldn't fix it completely. This issue is strongly related to the Visual Studio implementation, and since we cannot interfere with Visual Studio's internal mechanisms, we cannot fix this issue on our side.
If the issue is important for you, we recommend you convert your Web Site project to a Web Application project. Web Application projects work much faster.