Tree View Problem

[aamir55]

i m working on a small application
its main function is to create a album and then add photos in the album.
i m using tree view for creating album and photos
i m using tree root as album and nodes as photos.
i have to also show photos when i click on photo name
i m using function showphoto for this purpose
i m using sql server to store picture in database and then retrieve from it
but i also want to generate thumbnail when i click on album name and all the images should be displayed as thumbnail on picbox
is there any control for this purpose or how i can do that?

Private Sub ShowPhoto(ByVal item As TreeItem)
Try
' Create a command to select the selected photo
Dim strCmd As String = [String].Format("SELECT photo FROM Photos WHERE id = {0}", item.Id)
Dim cmd As New SqlCommand(strCmd, sqlConn)

' Set the description
lblDesc.Text = item.Desc

' Get bytes return from stored proc
Dim b As Byte() = CByte(cmd.ExecuteScalar())
If b.Length > 0 Then
' Open a stream for the image and write the bytes into it
Dim stream As New System.IO.MemoryStream(b, True)
stream.Write(b, 0, b.Length)

' Draw photo to scale of picturebox
DrawToScale(New Bitmap(stream))

' Close the stream and delete the temp file
stream.Close()
End If
Catch e As Exception
MessageBox.Show(e.Message)
End Try
End Sub

if i use above function to show photo
error comes on this line
Dim b As Byte() = CByte(cmd.ExecuteScalar())
and erroe says"Error 1 Value of type 'Byte' cannot be converted to '1-dimensional array of Byte'"
if i remove Cbyte from above line then application runs well but when i click on photo name then picture doesn't appear in picturebox.
and i m using showphoto function in below code snipts

Private Sub treeAlbum_AfterSelect(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles treeAlbum.AfterSelect
Try
' Disable edit controls if we were in edit mode
If True = btnUpdate.Visible Then
btnUpdate.Visible = False
txtDesc.Visible = False
lblDesc.Visible = True
End If

' Retrieve the item info for this node
Dim item As TreeItem = DirectCast(e.Node.Tag, TreeItem)

' If the selected item is an album...
If ItemType.Album = item.Type Then
lblDesc.Text = item.Desc
' Set the description
PictureBox.Image = Nothing
' Clear the image
Return
End If

' ...otherwise it is a photo
ShowPhoto(item)
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Sub
plz help me