C# Signature:
[DllImport("ole32.dll")]
static extern int PropStgNameToFmtId([MarshalAs(UnmanagedType.LPWStr)]
string oszName, out FMTID pfmtid);
VB.Net Signature:
<DllImport("ole32.dll", preservesig:=False)> _
Friend Shared Function PropStgNameToFmtId( _
<MarshalAs(UnmanagedType.LPWStr)> ByVal oszName As String, _
<Out()> ByRef FMTID As Guid) As Integer
End Function
User-Defined Types:
None.
Notes:
None.
Tips & Tricks:
To generate a FormatIdentifier from a custom PropertyStorage name use the following in VB.Net:
Dim characters As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345"
Dim name As String = "MyPropertyStorageName
Dim bits As BitArray
Dim i As Integer
Dim j As Integer
Dim index As Integer
Dim idBytes() As Byte
Dim idBits As BitArray
idBits = New BitArray(130) '26 * 5 - 26 Characters @ 5bits each
name = name.ToUpper
For i = 0 To name.Length - 1
'Get the index of the current character and convert it to
'a BitArray with a length of five (MaxValue = 31 hence the
'character restriction
index = characters.IndexOf(name.Chars(i))
If index < 0 Then
Throw New ApplicationException("Invalid Character")
End If
bits = New BitArray(New Byte() _
{CByte(index)})
For j = 0 To 4
idBits(j + (5 * i)) = bits(j)
Next
Next
'A new Guid requires an array of exactly 16 bytes
'Split the first 128 bits of the array into 8 bit chunks
For i = 0 To 15
ReDim Preserve idBytes(i)
bits = New BitArray(8)
For j = 0 To 7
bits(j) = idBits(j + (8 * i))
Next
idBytes(i) = CByte(BitsToInteger(bits))
Next
Dim fmtId As New Guid(idBytes)
Guids generated with this will return the name using the FmtIdToPropStgName Function, and can be used to generate a new IPropertyStorage interface with IPropertySetStorage.Create(). The name returned will be filled to 26 chars with the letter 'a' due to the fixed size of a Guid and the fact that we're passing all zeros in the BitArray after the name finishes to reach this size.
The following helper function is also required:
Friend Function BitsToInteger(ByVal bits As BitArray) As Integer
Dim int As Integer = 0
Dim i As Integer
For i = 0 To bits.Count - 1
If bits(i) Then
int += 2 ^ i
End If
Next
Return int
End Function
See Also: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/stg/stg/names_in_istorage.asp
Sample Code:
Please add some!
Alternative Managed API:
Do you know one? Please contribute it!
