How do I generate a random time between 12AM and 6PM in C#?

I am trying to generate a random time between 12AM and 6PM. So far I tried the following code:

Random random = new Random();

TimeSpan startWorkDay = new TimeSpan(5, 0, 0);
TimeSpan endWorkDay = new TimeSpan(12, 0, 0);

TimeSpan numberOfMinutes = endWorkDay - startWorkDay;
TimeSpan timeSpan = new TimeSpan(0, random.Next(0, (int)numberOfMinutes.TotalMinutes), 0);

DateTime flightTimeSpan = startWorkDay + timeSpan;

for (int i = 0; i < 10; i++)
{
    Console.WriteLine(flightTimeSpan.ToString("hh:mm tt"));
}

what am I doing wrong?

EDIT: The code provided above is saying that I cannot implicitly convert System.TimeSpan to System.DateTime