Running Sharepoint PowerShell from C# code

Check this out to activate features in C#:

http://www.dotnetmafia.com/blogs/dotnettipoftheday/archive/2008/02/22/how-to-programmatically-activate-a-feature.aspx

And a list of SharePoint OOTB feature guids:

http://blogs.msdn.com/b/mcsnoiwb/archive/2010/01/07/features-and-their-guid-s-in-sp2010.aspx

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If you really want to run PowerShell from C#:

http://www.codeproject.com/Articles/18229/How-to-run-PowerShell-scripts-from-C

Don't forget to add the SharePoint snapin to expose the cmdlets:

Add-PSSnapin Microsoft.SharePoint.PowerShell

PowerShell & C# are two languages you can use to access the SharePoint Object Model. Depending upon the kind of task you want to perform on SharePoint platform, you can choose any one. In general, almost every task is achievable using C# or Powershell

Using C#, If you want to activate a feature when a new site is created, below is the code you can use in WebProvisioned Event Receiver.

Guid featureGuid = new Guid(YourFeatureGUID);
if (web.Features[featureGuid] == null) 
{
         web.Features.Add(featureGuid);
}

By the way, I would recommend to create the site using Publishing Site definition so that you get all publishing features activated by default.