VB6 GMTOffset到C＃

Question

I am trying to convert the code below from VB6 to C#. I am just not sure where to begin, I guess maybe because I am sucked way to much into VB6 and can't seem to take a step back.

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, obviously don't want to do PInvoke in .NET but rather use the pure objects in the .NET Framework.

Answer 1

Based on your code, you are looking for something along the lines of:

        var dtNow = DateTime.Now;
        var dtOffset = (dtNow.ToUniversalTime().Subtract(dtNow)).TotalMinutes / 15;

You may need to adjust the offset negatively if the universal time is greater than the current system time.

Answer 2

The system time:

DateTime systemDateTime = DateTime.Now;

But more importantly, the offset the system is running with:

TimeZoneInfo systemTimeZone = TimeZoneInfo.Local;
TimeSpan offset = systemTimeZone.GetUtcOffset();
Int32 offsetMinutes = offset.Hours * 60 + offset.Minutes;

Answer 3

Near direct translation:

//Private Function GMT_OFFSET() As Integer
int GMT_OFFSET()
{
  //'****DECLARE VARIABLES
  //Dim dtNow As Date, dtEngland As Date
  DateTime dtNow, dtEngland;
  //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
  dtEngland = DateTime.UtcNow;
  dtNow = dtEngland.ToLocalTime;
  //'****RETURN QUARTER HOURS
  //GMT_OFFSET = DateDiff("n", dtEngland, dtNow) \ 15
  return Convert.ToInt32((dtNow - dtEngland).TotalMinutes) / 15;
//End Function
}

NB VB6's DateDiff(interval,date1,date2) results in intervals based upon date2 - date1 , not vice versa.

But the one-liner is:

return Convert.ToInt32(TimeZoneInfo.Local.GetUtcOffset(DateTime.UtcNow).TotalMinutes) / 15;