VBA Sample code
but You don't know what this is clsTimeConvert
C # How can I use?
VBA code to C # code i want to change.

Sub zenOn_ArchiveFilter()
'Declarations
Dim zArchive As Archive
Dim zArvFilter As ArchiveFilter
Dim zArvVars As ArchiveFilterVariables
Dim zTimeConvert As clsTimeConvert
Dim dTime As Double
Dim i As Integer

'Initialize zArchive with the first available archive
Set zArchive = thisProject.Archives.Item(0)

'If no archive is availabe, then ...
If zArchive Is Nothing Then
'... inform the user
MsgBox ("No archive available!")

Else
'Initialize zArvFilter by creating a new archive filter
Set zArvFilter = zArchive.ArchiveFilters.CreateArchiveFilter

'Every archive variable within the collection...
For i = 0 To zArchive.ArchiveVariables.Count - 1
'... will be added to the archive filter
zArvFilter.AddArchiveVariable zArchive.ArchiveVariables.Item(i)
Next i

'Initialize zTimeConvert by creating a new instance of the zenOn "clsTimeConvert" macro
Set zTimeConvert = New clsTimeConvert

'Set dTime by converting the desired system time into the zenOn compatible UTC time
dTime = zTimeConvert.System2zenOn(CDbl(CDate("30.07.2007 14:00:00")))
'Set the converted time as the start time for the filter
zArvFilter.StartTime = dTime

'Set dTime by converting the desired system time into the zenOn compatible UTC time
dTime = zTimeConvert.System2zenOn(CDbl(CDate("31.07.2007 11:15:00")))
'Set the converted time as the end time for the filter
zArvFilter.EndTime = dTime

'All I-BIT and HWERT bits
zArvFilter.StatusMask = &H41000 'Check only I-BIT + HWERT
zArvFilter.StatusBit = &H41000 'Return data if one of those bits are TRUE or both

'Initialize zArvVars by initiating a new filter query
Set zArvVars = zArvFilter.Query

'For every filtered variable within the result...
For i = 0 To zArvVars.Count - 1
With zArvVars.Item(i)
'... output the name of the variable ...
Debug.Print "Variable: " & .ArchiveVariable.Name
'... and the amount of I-BIT and HWERT bits within the specified time range
Debug.Print vbTab & "I-BIT + HWERT: " & .ArchiveValues.Count & vbNewLine
End With
Next i
End If
End Sub