How to the compress file

Following code explain how to compress file.

Public Sub CompressGivenFile(ByVal srcFile As String, ByVal destFile As String)
       
        Dim buffer As Byte() = Nothing
        Dim sourceStream As FileStream = Nothing
        Dim destinationStream As FileStream = Nothing
        Dim compressedStream As GZipStream = Nothing

        Try      
            sourceStream = New FileStream(sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read)
  
            buffer = New Byte(sourceStream.Length) {}
            Dim checkCounter As Integer = sourceStream.Read(buffer, 0, buffer.Length)
            destinationStream = New FileStream(destinationFile, FileMode.OpenOrCreate, FileAccess.Write)
       
            compressedStream = New GZipStream(destinationStream, CompressionMode.Compress, True)
        
            compressedStream.Write(buffer, 0, buffer.Length)

        Catch ex As ApplicationException
            MessageBox.Show(ex.Message, "An Error occured during compression", MessageBoxButtons.OK, MessageBoxIcon.Error)       
        End Try
 End Sub