This article demonstrates how to setting up developer's Visual Studio to make sure transformation works when deploying from local environment to DXP Integration. This works with DXP Windows environments (.Net Framework).
DXP deployment takes account "Configuration" name to correctly transform files. For example, if you're deploying to Production, it will combine your current "web.config" with "web.Production.config".
Correctly setting up Visual Studio
You have to create new configuration types in your development environment to match DXP's Integration, Preproduction and Production. Deploying with built-in "Debug" or "Release" will make your transformation file such as "web.Integration.config" be dismissed.
Please make sure you select "Copy settings from" is Release. Or else, excessive logging or diagnostics may exposed in public environments.
Deploy site using Visual Studio Publish feature
By default, generated VS publish profile will select "Release" and you need to make sure it's changed to "Integration" before publishing code to DXP.