BimlExpress is a Visual Studio extension that provides the ability to create Biml files, edit them in a custom code editor, and generate SSIS packages from Biml.
BimlExpress provides the ability to create packages from Biml, an XML-based language that allows you to describe your BI solution in a declarative fashion. This is similar to using HTML to describe how a web page should appear. In addition, you can embed BimlScript (C# or VB.NET code) into Biml, in the same way that ASP.NET works with HTML. This allows for large numbers of packages to be created with a minimal amount of code.
Learn Biml on BimlScript.com