Useful .Net stuff often overlooked

Ok, I need to write it down somewhere, the article has a lot of explanations, and I just want to record classes because I know what they are, but I will forget later.

The article is here: http://haacked.com/archive/2007/06/13/the-most-useful-.net-utility-classes-developers-tend-to-reinvent.aspx

Stuff to remember:

Combine path:

public string GetFullPath(string filename)
{
string folder = ConfigurationManager.AppSettings["somefolder"];
return System.IO.Path.Combine(folder, filename);
}

Get folder location:

someFolderPath + Path.DirectorySeparatorChar;

Get just the file name:

string fileName = Path.GetFileName(fullPath);

Get absolute path from virtual:

string path = VirtualPathUtility.ToAbsolutePath("~/Controls/Test.ascx");

Get new line separator (really neat one!) Environment.NewLine;

From comments:

Check if var is a number: Double.TryParse or Int.TryParse

Timing execution (not sure, but that's what it sounds like from the comment):
System.Diagnostics.Stopwatch

Query string: HttpUtility.ParseQueryString
Raw URL: HttpContext.Current.Request.RawUrl; (MSDN)

I am the megamosk

Calculate average of up to three scores (presence of a score is determined by the gradeN>0 condition).

CASE WHEN Topic1>0 THEN Grade1 +
CASE WHEN Topic2>0 THEN Grade2 +
CASE WHEN Topic3>0 THEN Grade3
ELSE 0 END
WHEN Topic3>0 THEN Grade3
ELSE 0 END
ELSE
CASE WHEN Topic2>0 THEN Grade2 +
CASE WHEN Topic3>0 THEN Grade3
ELSE 0 END
WHEN Topic3 > 0 THEN Grade3
ELSE 0 END
END AS TotalGrades
, CASE WHEN Topic1>0 THEN 1+
CASE WHEN Topic2>0 THEN 1+
CASE WHEN Topic3>0 THEN 1
ELSE 0 END
WHEN Topic3>0 THEN 1
ELSE 0 END
ELSE
CASE WHEN Topic2>0 THEN 1+
CASE WHEN Topic3>0 THEN 1
ELSE 0 END
WHEN Topic3>0 THEN 1
ELSE 0 END
END AS NumberOfTopics

Unfortunately, I do not know how to calculate the actual average (TotalGrades/NumberOfTopics), so I guess I am not the megamosk. Oh well...