[RESOLVED] Plotting Real Time Graph

[MaximilianMayrhofer]

Yes. Your system time.

[catherine0136]

Thanks MaximilianMayrhofer! =)

But i still dont really understanding the following, please forgive me as i may be poor in understanding.

For example:

Dim dt As DateTime = DateTime.Now       
 Dim ts As TimeSpan = dt - StartTime

        Label1.Text = ts.Hours.ToString & ":" & ts.Minutes.ToString & ":" & CInt(ts.Seconds).ToString
        ts = dt.AddSeconds(1) - StartTime

So for example, the time now is 4:01:35PM.

Since dt is (DateTime.Now), which is 4:01:35PM,
and ts is (dt-StartTime), so it will mean [ ts = (4:01:35) - StartTime ] correct?

But the StartTime, as in the beginning, 00:00:00 ?

Then for, ts = dt.AddSeconds(1) - StartTime, it will be :
>> ts = 4:01:35.AddSeconds(1) - 00:00:00
which will be:= 4:01:36 - 00:00:00

The above doesnt make sense to me, so I believe my concept towards the above is wrong, therefore i would appreciate if someone could explain to me how it works.

Apologies if the above is unclear. Because i cant really understand how the above subtraction will allow my timer to start from 00:00:00 , 00:00:01, 00:00:02, so on and so forth..

Thanks in advance for the help!
.

[boops boops]

But the StartTime, as in the beginning, 00:00:00 ?

If I remember correctly, there was a point earlier in the program where you had:

StartTime = DateTime.Now

So StartTime contains a snapshot of whatever the system time was at that particular moment. (Hint: if you don't know about using BreakPoints yet, it's a good time to learn it.)

DateTimes and TimeSpans are confusing because they are not like ordinary numbers. If you subtract two Integers you get another Integer as you'd expect:

Dim Lots As Integer = 1000
Dim NotSoMuch As Integer = Lots - 250
TextBox1.Text = NotSoMuch.ToString

and TextBox1 will obligingly show 750. It's exactly like you learned it in algebra. But if you try to subtract two DateTimes, you don't get another DateTime but a TimeSpan instead. You are allowed to use a minus sign for two DateTimes but it has a different meaning to the minus sign used for arithmetic. It's just the way people at Microsoft designed it. And you can't write:

Dim dt As DateTime = DateTime.Now
dt = dt + 5

Instead you have to use AddSeconds or SubtractSeconds. What is more dt.AddSeconds(5) doesn't change the value of dt the way + does with integers. Instead it produces a new DateTime with the required value.

Things like DateTime and TimeSpan are called Reference Types, as opposed to Value Types (like Integers). A String is another example of a reference type, and similarly it has rules of its own for "adding" strings together. You'll get used to them, I hope.

BB

[catherine0136]

@ BB,

Arh, i understand what you meant already!!

Thanks! =)