[c#] Convert Difference between 2 times into Milliseconds?

I have two masked TextBox controls and was wondering how I'd go about getting the time in each one and then converting the difference into milliseconds. Like, say in tb1 I write "12:01" and in tb2 I write "12:02", and then click a button. Once the button's clicked it starts a timer and at 12:02 a messagebox will be displayed. I know how to do all of it except for the time conversion part.

How can it be achieved?

If you just want to display a message box at 12:02, use a timer control with delay of, say, 250ms, that keeps checking if the current time is 12:02. When it is, display the message and stop the timer. Note this does not require a start time field (although you may be using that for something else -- I don't know -- in which case the other code provided to you here will be helpful).

var firstTime = DateTime.Now;
var secondTime = DateTime.Now.AddMilliseconds(600);
var diff = secondTime.Subtract(firstTime).Milliseconds;


// var diff = DateTime.Now.AddMilliseconds(600).Subtract(DateTime.Now).Milliseconds;

VB.net, Desktop application. If you need lapsed time in milliseconds:

Dim starts As Integer = My.Computer.Clock.TickCount
Dim ends As Integer = My.Computer.Clock.TickCount
Dim lapsed As Integer = ends - starts

To answer the title-question:

DateTime d1 = ...;
DateTime d2 = ...;
TimeSpan diff = d2 - d1;

int millisceonds = (int) diff.TotalMilliseconds;

You can use this to set a Timer:

timer1.interval = millisceonds;
timer1.Enabled = true;

Don't forget to disable the timer when handling the tick.

But if you want an event at 12:03, just substitute DateTime.Now for d1.

But it is not clear what the exact function of textBox1 and textBox2 are.

You have to convert textbox's values to DateTime (t1,t2), then:

DateTime t1,t2;
t1 = DateTime.Parse(textbox1.Text);
t2 = DateTime.Parse(textbox2.Text);
int diff = ((TimeSpan)(t2 - t1)).TotalMilliseconds;

Or use DateTime.TryParse(textbox1, out t1); Error handling is up to you.

Try:

DateTime first;
DateTime second;

int milliSeconds = (int)((TimeSpan)(second - first)).TotalMilliseconds;

If you are only dealing with Times and no dates you will want to only deal with TimeSpan and handle crossing over midnight.

TimeSpan time1 = ...;  // assume TimeOfDay
TimeSpan time2 = ...;  // assume TimeOfDay
TimeSpan diffTime = time2 - time1;
if (time2 < time1)  // crosses over midnight
    diffTime += TimeSpan.FromTicks(TimeSpan.TicksPerDay);
int totalMilliSeconds = (int)diffTime.TotalMilliseconds;

Many of the above mentioned solutions might suite different people.
I would like to suggest a slightly modified code than most accepted solution by "MusiGenesis".

DateTime firstTime = DateTime.Parse( TextBox1.Text );
DateTime secondTime = DateTime.Parse( TextBox2.Text );
double milDiff = secondTime.Subtract(firstTime).TotalMilliseconds;

Considerations:
- earlierTime.Subtract(laterTime) you will get a negative value.
- use int milDiff = (int)DateTime.Now.Subtract(StartTime).TotalMilliseconds; if you need integer value instead of double
- Same code can be used to get difference between two Date values and you may get .TotalDays or .TotalHours insteaf of .TotalMilliseconds

    public static Int64 GetDifferencesBetweenTwoDate(DateTime newDate, DateTime oldDate, string type)
    {
        var span = newDate - oldDate;
        switch (type)
        {
            case "tt": return (int)span.Ticks;
            case "ms": return (int)span.TotalMilliseconds;
            case "ss": return (int)span.TotalSeconds;
            case "mm": return (int)span.TotalMinutes;
            case "hh": return (int)span.TotalHours;
            case "dd": return (int)span.TotalDays;
        }
        return 0;
    }

Try the following:

   DateTime dtStart;
   DateTime dtEnd;

   if (DateTime.TryParse( tb1.Text, out dtStart ) && DateTime.TryParse(tb2.Text, out dtEnd ))
   {
      TimeSpan ts = dtStart - dtEnd;
      double difference = ts.TotalMilliseconds;
   }