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Issues with Using GetTimeZoneInformation Kernel function in VB.Net

Hello,
I am having trouble using GetTimeZoneInformation function in VB.Net.
Here is what I have

Private Declare Function GetTimeZoneInformation _
Lib "kernel32" (ByRef lpTimeZoneInformation As _
TIME_ZONE_INFORMATION) As Long

Private Structure TIME_ZONE_INFORMATION
Dim bias As Long
Dim StandardName() As Byte
Dim StandardDate As SYSTEMTIME
Dim StandardBias As Long
Dim DaylightName() As Byte
Dim DaylightDate As SYSTEMTIME
Dim DaylightBias As Long
Public Sub Initialize()
ReDim StandardName(63)
ReDim DaylightName(63)
End Sub
End Structure

Here is where I am calling the function from

Public Function convertToGmt(ByVal st As String) As String
Dim nRet As Long
Dim bias As Long
Dim tz As TIME_ZONE_INFORMATION
st = Format(st, "General Date")
tz.Initialize()
nRet = GetTimeZoneInformation(tz) 'Getting Error At this line
End Function

Error is
An unhandled exception of type 'System.NullReferenceException' occurred in OBTMTrackingTool.exe
Additional information: Object reference not set to an instance of an object.

PLEASE HELP!! Tried No of things and could't figure it out.I really appreciate your help and Thanks in Advance

davidrichardson

Just Found this havent tried it

Structure SYSTEMTIME
Dim wYear As Short
Dim wMonth As Short
Dim wDayOfWeek As Short
Dim wDay As Short
Dim wHour As Short
Dim wMinute As Short
Dim wSecond As Short
Dim wMilliseconds As Short
End Structure

Private Structure TIME_ZONE_INFORMATION
Dim bias As Long
Dim StandardName() As Byte
Dim StandardDate As SYSTEMTIME
Dim StandardBias As Long
Dim DaylightName() As Byte
Dim DaylightDate As SYSTEMTIME
Dim DaylightBias As Long
Public Sub Initialize()
ReDim StandardName(63)
ReDim DaylightName(63)
End Sub
End Structure

Private Declare Function GetTimeZoneInformation Lib "kernel32" (ByVal ByReflpTimeZoneInformation As Form1.TIME_ZONE_INFORMATION) As Integer
Public Function convertToGmt(ByVal st As String) As String
Dim nRet As Long
Dim bias As Long
Dim tz As TIME_ZONE_INFORMATION
st = Format(st, "General Date")
tz.Initialize()
nRet = GetTimeZoneInformation(tz)
End Function

Sireesha

ASKER

Thanks.I think there is something wrong with the way I am using arrays b'z when I comment them out I am not getting an error when calling nRet = GetTimeZoneInformation(tz) but the bias values are not right.So I need to get this line working with the existing structure.

Sireesha

ASKER

Also missed to Include SYSTEMTIME structure that I am using

Private Structure SYSTEMTIME
Dim wYear As Integer
Dim wMonth As Integer
Dim wDayOfWeek As Integer
Dim wDay As Integer
Dim wHour As Integer
Dim wMinute As Integer
Dim wSecond As Integer
Dim wMilliseconds As Integer
End Structure

Joe_Griffith

Why not just use the built in System.TimeZone class and avoid the whole problem?

Sireesha

ASKER

I need to use this to scheduled the customer call backs with the Melita dialers.Thanks.

DotNetLover_Baan

Private Declare Function GetTimeZoneInformation Lib "kernel32" (ByVal ByReflpTimeZoneInformation As Form1.TIME_ZONE_INFORMATION) As Integer
Public Function convertToGmt(ByVal st As String) As String
Dim nRet As Long
Dim bias As Long

Dim tz As New TIME_ZONE_INFORMATION 'Add 'New' to the instantiation

st = Format(st, "General Date")
tz.Initialize()
nRet = GetTimeZoneInformation(tz)
End Function

The NullException occurs because there is no object of the timezone class, since u haven't used New...

-Baan

Sireesha

ASKER

Thanks Baan.I am sure about using New keyword to instantiate but I didn't find any difference and thought that I was still getting this error.One difference that I didn't try was using Form1.Time_zone_information in the function declaration.I will try that and as well as New keyword to instantiate the timezone on Monday when I get back to work and let you know how it goes.Thanks for your help.

Sireesha

ASKER

Somebody at this link made my day today.
Here is the working code if anybody is interested.Look for the changed in Time_zone_Information Structure I really appreciate any help that you have provided.

http://www.dotnet247.com/247reference/msgs/20/100758.aspx

Private Declare Function GetTimeZoneInformation _
Lib "kernel32" (ByRef lpTimeZoneInformation As _
TIME_ZONE_INFORMATION) As Long
Structure SYSTEMTIME
Dim wYear As Short
Dim wMonth As Short
Dim wDayOfWeek As Short
Dim wDay As Short
Dim wHour As Short
Dim wMinute As Short
Dim wSecond As Short
Dim wMilliseconds As Short
End Structure

Private Structure TIME_ZONE_INFORMATION
Dim Bias As Integer
<VBFixedString(64), System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst:=64)> Public StandardName As String
Dim StandardDate As SYSTEMTIME
Dim StandardBias As Integer
<VBFixedString(64), System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst:=64)> Public DaylightName As String
Dim DaylightDate As SYSTEMTIME
Dim DaylightBias As Integer
End Structure
Private Const TIME_ZONE_ID_INVALID = &HFFFFFFFF
Private Const TIME_ZONE_ID_UNKNOWN = 0
Private Const TIME_ZONE_ID_STANDARD = 1
Private Const TIME_ZONE_ID_DAYLIGHT = 2
Public Function convertToGmt(ByVal st As String) As String
On Error Resume Next
Dim nRet As Long
Dim bias As Long
Dim tz As TIME_ZONE_INFORMATION
st = Format(st, "General Date")

nRet = GetTimeZoneInformation(tz)

If nRet <> TIME_ZONE_ID_INVALID Then
Select Case nRet
Case TIME_ZONE_ID_UNKNOWN
MsgBox("Unknown Time Zone", , "Error!")
Case TIME_ZONE_ID_STANDARD
bias = tz.bias + tz.StandardBias
Case TIME_ZONE_ID_DAYLIGHT
bias = tz.bias + tz.DaylightBias
End Select
convertToGmt = DateAdd("n", bias, st)
End If
End Function

Sireesha

ASKER

How do I close this one now since I found the resolution on a different site?Thanks

ASKER CERTIFIED SOLUTION

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