A recent bug entered via MSDN Product Feedback Center questions the current behavior of add new item with respect to the class template.  In particular, if a class is added to a project then references to System.dll, System.Data.dll, and System.XML.dll are added automatically.  This can certainly be a frustrating experience if the project doesn’t require those references and the developer is trying to keep the set of references pristine. 

There are a couple of reasons for the current design.  First, there is a bit of historical reasoning.  Both VS 2002 and VS 2003 supported this behavior.  When we authored the item templates for VS 2005 we decided that we would only make functionality changes when we had received substantial feedback that the model or content was poor.  Since we didn’t have that feedback about the reference addition, we didn’t make the change.  The second reason has to do with a combination of the popularity of those particular references plus the behavior of a feature that we added to C# in VS 2005 called ‘add using’.  Add using will proffer a smart tag on a type which allows a using directive to be automatically added to the file/namespace that you’re working in; however, it requires that the assembly which contains that type already be referenced by the project.  Given that these two assemblies contain types which are extremely common in a number of projects, we decided that continuing to add them automatically would enhance the experience.  It’s also important to note that the C# compiler will not emit references to assemblies when the code that is being compiled does not contain any of the types defined in those assemblies (so there isn’t really an additional cost outside of readability for having those particular assemblies referenced). 

Given that we still haven’t received a lot of feedback outside of the bug mentioned above, we’re going to keep the behavior the same for the moment (obviously if we receive more feedback we’ll reconsider).  However, the good news is that it’s possible to customize this behavior fairly easily.  The C# item templates that are shipped with Visual Studio are installed to %Program Files%\Microsoft Visual Studio 8\Common7\IDE\ItemTemplates\CSharp\1033.  The Add | Class… template is in the Class.zip file.  There are two files in the zip; the Class.cs file is the general shape of the generated file.  It has a few replacement strings inside of it that are determined based on the “Root namespace” of the project, or the filename the is chosen when the class is added.  The Class.vstemplate file is a description of the contents of the template, and allows the icon, description, etc. of the class template to be changed (these are displayed in the Add New Item… dialog).  The .vstemplate file also contains the list of references to use when a new class is added to the project.  In order to change this behavior, simply change:

      <Reference>

            <Assembly>System</Assembly>

      </Reference>

      <Reference>

            <Assembly>System.Data</Assembly>

      </Reference>

      <Reference>

            <Assembly>System.Xml</Assembly>

      </Reference>

to:

      <Reference>

            <Assembly>System</Assembly>

      </Reference>

      <!--<Reference>

            <Assembly>System.Data</Assembly>

      </Reference>

      <Reference>

            <Assembly>System.Xml</Assembly>

      </Reference>-->

Then re-zip the contents and close all instances of Visual Studio.  Then run devenv /setup (from the %Program Files%\Microsoft Visual Studio 8\Common7\IDE directory).  I didn't try it, but it should be possible to run devenv /InstallVSTemplates instead which sould execute faster.  This will recreate the cache that VS uses to store the unzipped versions of the item templates.  When this is done, start VS.  The Add | Class… item template will no longer add a reference to System.Data.dll or System.Xml.dll to your project.