Luckily, Windows and Outlook allow developers to develop and implement custom preview handlers for any file type, which after registering the handlers, users can instantly gain preview capabilities for those file types in Outlook and Windows. Windows and Office Preview Handler Pack is one such custom previewers or preview handlers that provides support for .cs, .aspx and .sql source codes. With the handler pack installed, you can just click on the file ending with extension of .cs, .aspx and .sql with preview pane on, and instantly view the file content in the preview pane.
Windows and Office Preview Handler Pack can be downloaded CodePlex. To install it you will need run the installer as Administrator. Beside, if you have any other file types in mind that you would like to has the preview ability too, simply tell the author and he may include the support for that file ext.
If you would like previewers and preview handlers for PDF, XML, ZIP, MSI, BIN, CSV, XPS, and XAML files so that you can also preview the files without opening the files in Windows or Outlook, download sample previewers (PreviewHandlers2007_01.exe) from Microsoft. It comes with source code of handler framework which can be ignored. To install the preview handlers, make sure you right click on it, and choose Run as Administrator.