ASP.NET Web Deployment Using Visual Studio

Generally when you develop an application, you run it and test it in Visual Studio. By default, web application projects in Visual Studio 2017 use IIS Express as the development web server. IIS Express behaves more like full IIS than the Visual Studio Development Server (also known as Cassini), which Visual Studio 2017 uses by default. But neither development web server works exactly like IIS. Consequently, an app could run and test correctly in Visual Studio but fail when it's deployed to IIS.