You use Microsoft Visual Studio 2010 and Microsoft .NET Framework 4 to create an application. The
application connects to a Microsoft SQL Server 2008 database. The application contains two
SqlCommand objects named cmd1 and cmd2. You need to measure the time required to execute
each command. Which code segment should you use?

A.
Stopwatch w1 = new Stopwatch();
w1.Start();
cmd1.ExecuteNonQuery();
w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);
w1.Start();
cmd2.ExecuteNonQuery();
w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);

B.
Stopwatch w1 = new Stopwatch();
w1.Start();
cmd1.ExecuteNonQuery();
w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);
w1.Reset();
cmd2.ExecuteNonQuery();
w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);

C.
Stopwatch w1 = Stopwatch.StartNew();
cmd1.ExecuteNonQuery();
w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);
w1.Start();
cmd2.ExecuteNonQuery();
w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);

D.
Stopwatch w1 = Stopwatch.StartNew();
cmd1.ExecuteNonQuery();

w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);
w1 = Stopwatch.StartNew();
cmd2.ExecuteNonQuery();
w1.Stop();
Trace.WriteLine(w1.ElapsedMilliseconds);

Explanation:
A & C do not reset the stopwatch before running cmd2. B does not start the stopwatch after
resetting the stopwatch Start() does not reset the stopwatch, whereas StartNew() will create a new
instance of the Stop watch and initialise the elapsed time to Zero.
Stopwatch Class
(http://msdn.microsoft.com/en-us/library/system.diagnostics.stopwatch.aspx)