Copy A File Using Async

How do you copy a file Async  using the following code?  It appears to only work with Non-Binary files (.txt, etc.).  I'd like to be able to copy any kind of file.

Shared Async Function CopyFile(inSourceFile As String,
                                   inTargetFolder As String,
                                   Optional inRetainDateTime As Boolean = True) As Task
        ExceptionThrown = False
        ExceptionDefinition = ""

        Dim TargetFile As String = inTargetFolder + "\" + GSFileInfo.ParseFileName(inSourceFile, False)
        Dim SourceDateTime As Date = File.GetLastWriteTime(inSourceFile)

        Try
            Using SourceStream As FileStream = File.Open(inSourceFile, FileMode.Open)
                Using DestinationStream As FileStream = File.Create(TargetFile)
                    Await SourceStream.CopyToAsync(DestinationStream)
                End Using
            End Using

            If inRetainDateTime Then
                File.SetLastWriteTime(TargetFile, SourceDateTime)
            End If

        Catch ex As Exception
            ExceptionThrown = True
            ExceptionDefinition = ex.Message
        End Try
    End Function