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Problem reading small icon from database

I have an application with a document management form. When users add
documents to the form, I call the API function SHGetFileInfo to get
the associated large and small icons for the file. These icons are
added to two ImageList objects which are bound to a ListView control,
and everything looks great. I am saving the icons to a SQL Server
table by using Icon.Save to a stream and assigning the byte array to
the field, then loading them back when I open the form.

Here's the problem: the large icons load fine but the small ones give
an error stating "Invalid Parameter Used". Below are the two routines
for saving and loading the icons:

Public Function IconToBytes(ByV al icon As Icon) As Byte()
'Converts an Icon object into an array of bytes so
'it can be saved to a database field
Dim loMemoryStream As New IO.MemoryStream
icon.Save(loMem oryStream)
Dim laIcon(loMemory Stream.Length - 1) As Byte
loMemoryStream. Position = 0
loMemoryStream. Read(laIcon, 0, loMemoryStream. Length)
Return laIcon
End Function

Public Function DataFieldToImag e(ByVal oField As Object) As Image
'Converts an array of bytes to an Icon object when read
'from a database field.
If Not IsDBNull(oField ) Then
Dim laImage() As Byte = oField
Dim loMemoryStream As New IO.MemoryStream (laImage)
Return Image.FromStrea m(loMemoryStrea m)
Return Nothing
End If
End Function

I could not figure out how to load directly into an Icon object, so it
is loading into an Image object. Does ImageFormat.Ico n require 32x32
to create, and if so, why am I able to assign it using
Icon.FromHandle (SHI.hIcon) when I use SHGetFileInfo to retrieve the
icons; I suppose because the icon already exists in memory?

I tried using the routine below with various image formats to save in
something other than Icon format but the transparency is always lost,
and since I am loading Icons, I can't set the ImageList Transparent
color, as I need true transparency.

For now, I am using the large icon for both large and small image
lists and letting the small image list shrink the image to 16 x 16.
But, the image quality is not as good.

Any advise would be greatly appreciated. Thanks in advance.
Nov 20 '05 #1
0 1478

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