But DataTable doesn't derive from ComponentModel.Component.
Of course the ability to open the file in designer mode allows you to do really useful things like adding a button to a DataTable :-}

>I don't think there's any way around this short of modifying the default file types in Visual Studio. This behavior exhibits for any class that derives off Component - which is quite a few of the older classes.
>
>Pretty annoying but easy enough to work around.
>
>+++ Rick ---
>>Hi,
>>
>>Never noticed this before but say I create a .cs file with just this:

class SomeClass {}
>>class DTClass : System.Data.DataTable { }

The presence of the DataTable derived class (even though it is not the first in the file) causes VS to show this in Solution Explorer with the 'Component' icon' rather than the expected 'C#'
>>
>>As an added annoyance it also includes the 'View Designer' option in the context menu and, of course, using this fails because the DTClass is not the first class in the file. Can't seem to find a way to avoid this behaviour - but at least it doesn't attempt to open the Designer view by default....