Thursday, January 31, 2013

Visual Studio: Multiple Startup Projects

I’ve been using Visual Studio for over 10 years, but still keep on learning new tricks. That’s because I learn things very slowly dear reader! Today’s ‘wow, I didn’t know you could do that moment’, was finding out that it’s possible to launch multiple startup projects when one hits F5 – or Control-F5 in this case.

My scenario is that I’m writing a little spike for a distributed application. Each of my services is implemented as a console app. During development, I want to run integration tests where the services all talk to each other, so before running the tests I want to run all the services. Now I’m used to right-clicking on a project and choosing ‘Set as startup project’, but you can’t select multiple projects this way and it’s very tedious to launch multiple projects by going to each one in turn, setting it as the startup project, and then hitting ctrl-F5. What I didn’t know is that you can right click on the Solution node, select ‘Set Startup Projects’ and you get this dialogue:


You can then select multiple startup projects and choose any number of them to ‘Start without debugging’.

Now I can hit ctrl-F5 and all my little services start up. Wonderful.

Wednesday, January 16, 2013

Converting Between Unix Time And DateTime

Unix time is the time value used in Unix based operating systems and is often exposed by Unix based APIs. To convert it to, or from, a .NET System.DateTime simply calculate the number of seconds since the Unix Epoch, midnight on the 1st January 1970. I’ve created a little class you can use to do just that. Note that the Unix Epoch is UTC, so you should always convert your local time to UTC before doing the calculation.

public class UnixTime
private static readonly DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

public static long FromDateTime(DateTime dateTime)
if (dateTime.Kind == DateTimeKind.Utc)
return (long)dateTime.Subtract(epoch).TotalSeconds;
throw new ArgumentException("Input DateTime must be UTC");

public static DateTime ToDateTime(long unixTime)
return epoch.AddSeconds(unixTime);

public static long Now
return FromDateTime(DateTime.UtcNow);

You can convert from Unix time to a UTC DateTime like this:

var calculatedCurrentTime = UnixTime.ToDateTime(currentUnixTime);

Convert to Unix time from a UTC DateTime like this:

var calculatedUnixTime = UnixTime.FromDateTime(myDateTimeValue);

And get the current time as a UTC time value like this:

As an interesting aside, the 32 bit signed integer used in older Unix systems will overflow at 14 minutes past 3 o’clock and 7 seconds on the morning of 19th January 2038 and interpret the date as 1901. I shall come out of retirement and spend happy well paid hours as a ‘unix time consultant’. 64 bit systems will overflow in the year 292,277,026,596.