GMT Offset

[Techno]

Hi.

im trying to convert this code into C# but not sure where to begin. maybe because ive been too sucked into VB6!

Private Function GMT_OFFSET() As Integer
    '****DECLARE VARIABLES
    Dim dtNow As Date, dtEngland As Date
    Dim dtGMT As SYSTEMTIME
    '****GET SYSTEM TIME INFORMATION
    Call GetSystemTime(dtGMT)
    dtNow = Now
    dtEngland = dtGMT.wYear & "-" & dtGMT.wMonth & "-" & dtGMT.wDay & " " & dtGMT.wHour & ":" & dtGMT.wMinute & ":" & dtGMT.wSecond
    '****RETURN QUARTER HOURS
    GMT_OFFSET = DateDiff("n", dtEngland, dtNow) \ 15
End Function

I know GetSystemTime is a Win32 API but I am sure we dont need to do PInvoke in C# but instead just use the DateTime/TimeSpan objects and the globalization is needs be.

if the above can be translated into VB.NET then thats fine, I can easily translate to C# (but be sure it is using pure .NET)

[MattP]

You could just use TimeZone.GetUtcOffset

[.paul.]

try this:

TimeSpan ts = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now);
String tsString = ts.ToString();
MessageBox.Show(tsString);

[Techno]

Thanks. so how would I then convert the VB6 code into VB.NET or C#?

This is what I have in C# and it seems to work but fear that it maybe incorrect

 DateTime dtNow = DateTime.Now;
            DateTime dtEngland = DateTime.UtcNow;
            int gmtOffset = Convert.ToInt32((dtNow - dtEngland).TotalMinutes) / 15;

VB.NET:

Dim dtNow as DateTime = DateTime.Now
Dim dtEngland = DateTime.UtcNow
Dim gmtOffset = Convert.ToInt32((dtNow - dtEngland).TotalMinutes) / 15

[MattP]

Here are a couple of ways of getting the GMT Offset.

            int gmtOffset = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now).Hours;
            int gmtOffset2 = (DateTime.Now - DateTime.UtcNow).Hours;

Not sure if daylight savings is an issue but here's how to find out if it is daylight savings time

var isDaylightSavings = TimeZoneInfo.Local.IsDaylightSavingTime(DateTime.Now);

[Techno]

thanks, yes I thought as much. but im trying to convert the actual code to VB.NET/C#. I guess "n" is minutes which would equate to TotalMinutes.
I dont think DLS is an issue here. But the difference between UTC time (england) and the current date/time of the system (wherever the system is in the world) and then divide by 15 to return quarter hours

[MattP]

I guess "n" is minutes which would equate to TotalMinutes.

The 1st parameter of DateDiff is interval with "n" being minutes. Documentation: DateDiff Function.

To get an exact translation of this in C# you need to reference Microsoft.VisualBasic. Seems like a lot of work to me to get the TotalMinutes / 15.

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        [DllImport("kernel32.dll")]
        static extern void GetSystemTime(out SYSTEMTIME lpSystemTime);

        private void Form1_Load(object sender, EventArgs e)
        {
            int gmtOffset = GMT_OFFSET();
        }

        private int GMT_OFFSET()
        {
            DateTime dtNow = DateTime.Now;
            SYSTEMTIME dtGMT;
            GetSystemTime(out dtGMT);
            DateTime dtEngland = new DateTime(dtGMT.wYear, dtGMT.wMonth, dtGMT.wDay, dtGMT.wHour, dtGMT.wMinute, dtGMT.wSecond);
            return (int)(Microsoft.VisualBasic.DateAndTime.DateDiff("n", dtEngland, dtNow) / (long)15);
        }
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct SYSTEMTIME
    {
        public short wYear;
        public short wMonth;
        public short wDayOfWeek;
        public short wDay;
        public short wHour;
        public short wMinute;
        public short wSecond;
        public short wMilliseconds;
    }

Edit: seems like there's an off by 1 error in there somewhere as I'm getting -23 where I'd expect -24. (-6 * 4). Not too concerned as I'd just multiply the hours returned by methods provided above by 4 to get the quarter hours rather than this.

[Techno]

thanks. yeh, dont wanna do PInvoke! or even reference the VB library in C#

[MattP]

thanks. yeh, dont wanna do PInvoke! or even reference the VB library in C#

But I spent minutes writing up that example showing how efficient it was to not use current .NET methods to do things!

[Techno]

whilst I do appreciate it, it certainly is not best practice. There is a reason why you shouldnt still use "old style code" when using .NET.
you will find later on that the VB reference library will be obsolete meaning your app in future when upgrading will be wortheless without having to go through another cycle of maintainence, which costs both time and money

[MattP]

whilst I do appreciate it, it certainly is not best practice. There is a reason why you shouldnt still use "old style code" when using .NET.
you will find later on that the VB reference library will be obsolete meaning your app in future when upgrading will be wortheless without having to go through another cycle of maintainence, which costs both time and money

Um...yeah. I should really finish up statements like that with </sarcasm> just to make sure.

[Techno]

ah!