A faster file.copy VB convert give "empty path name is not legal error"

"empty path name is not legal Error"

Public Shared Sub MoveTime(ByVal source As String, ByVal destination As String)
    Dim start_time As DateTime = DateTime.Now
    FMove(source, destination)
    Dim size As Long = New FileInfo(destination).Length
    Dim milliseconds As Integer = 1 + CInt(((DateTime.Now - start_time).TotalMilliseconds))
    Dim tsize As Long = size * 3600000 / milliseconds
    tsize = tsize / CInt(Math.Pow(2, 30))
    Console.WriteLine(tsize & "GB/hour")
End Sub

Private Shared Sub FMove(ByVal source As String, ByVal destination As String)
    Dim array_length As Integer = CInt(Math.Pow(2, 19))
    Dim dataArray As Byte() = New Byte(array_length - 1) {}

    Using fsread As FileStream = New FileStream(source, FileMode.Open, FileAccess.Read, FileShare.None, array_length)

        Using bwread As BinaryReader = New BinaryReader(fsread)

            Using fswrite As FileStream = New FileStream(destination, FileMode.Create, FileAccess.Write, FileShare.None, array_length)

                Using bwwrite As BinaryWriter = New BinaryWriter(fswrite)

                    While True
                        Dim read As Integer = bwread.Read(dataArray, 0, array_length)
                        If 0 = read Then Exit For
                        bwwrite.Write(dataArray, 0, read)
                    End While
                End Using
            End Using
        End Using
    End Using

    File.Delete(source)
End Sub
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    Dim Sourcefolder As String = FolderBrowserDialog1.SelectedPath
    Dim Tragetfolder As String = FolderBrowserDialog2.SelectedPath
    FMove(Sourcefolder, Tragetfolder)
End Sub