Compress The File Without Loosing File Extension Inside Compressed File

I have File Like "Sample.bak" and when I compress it to be "Sample.zip" I lose the file extension inside the zip file I meann when I open the compressed file I find "Sample" without any extension.

I use this code :

Dim name As String = Path.GetFileName(filePath).Replace(".Bak", "")
Dim source() As Byte = System.IO.File.ReadAllBytes(filePath)
Dim compressed() As Byte = ConvertToByteArray(source)
System.IO.File.WriteAllBytes(destination & name & ".Bak" & ".zip", compressed)

Or using this code :

Public Sub cmdCompressFile(ByVal FileName As String)

'Stream object that reads file contents
Dim streamObj As Stream = New StreamReader(FileName).BaseStream

[CODE]...

I need to compress the file without loosing file extension inside compressed file.