The XML Web Service Layer

You can introduce a similar upload strategy through a dedicated XML Web service and Windows client. The XML Web service plays the same role as the ASP.NET Web page: It accepts a buffer of bytes and writes them to the OrderProcessor directory. At this point, the OrderProcessor takes over. Listing 16-16 shows the XML Web service.

Listing 16-16 The Excel upload XML Web service

 Public Class OrderService     Inherits System.Web.Services.WebService       <WebMethod()> _     Public Sub UploadExcelFile(ByVal filename As String, _      ByVal bytes As Byte())         ' Determine the location and name for the new file.         Dim SavePath As String         SavePath = ConfigurationSettings.AppSettings("MonitorPath")         SavePath &= "\" & filename         ' Create a FileStream.         Dim fs As New FileStream(SavePath, FileMode.CreateNew)         ' Write the received bytes to the file.         fs.Write(bytes, 0, bytes.Length)         fs.Close()     End Sub End Class 

The Windows client provides the functionality for selecting a file and transmitting it to the XML Web service (as shown in Figure 16-10).

Figure 16-10. The Windows upload client

The code shown in Listing 16-17 is similar to the ASP.NET upload page, although the file selection is provided through the OpenFileDialog class.

Listing 16-17 The Windows client form code

 Public Class WindowsClient     Inherits System.Windows.Forms.Form     Friend WithEvents cmdBrowse As Button     Friend WithEvents cmdUpload As Button     Friend WithEvents Label1 As Label     Friend WithEvents lblInfo As Label     Friend WithEvents dlgOpenFile As OpenFileDialog     Friend WithEvents txtFile As TextBox     Private Sub cmdBrowse_Click(ByVal sender As System.Object, _      ByVal e As System.EventArgs) Handles cmdBrowse.Click         dlgOpenFile.ShowDialog()         txtFile.Text = dlgOpenFile.FileName     End Sub     Private Sub cmdUpload_Click(ByVal sender As System.Object, _      ByVal e As System.EventArgs) Handles cmdUpload.Click         ' Check that a file is actually being submitted.         If txtFile.Text = "" Then             lblInfo.Text = "No file specified."         ElseIf Not txtFile.Text.EndsWith(".xls") Then             lblInfo.Text = "You can only upload Excel files."         Else             Dim fs As FileStream             Try                 ' Create the byte array.                 fs = New FileStream(txtFile.Text, FileMode.Open)                 Dim Bytes As Byte()                 ReDim Bytes(fs.Length)                 fs.Read(Bytes, 0, fs.Length)                 ' Submit the byte array to the XML Web service.                 Dim Proxy As New localhost.OrderService()                 Dim FileName As String = Path.GetFileName(txtFile.Text)                 Proxy.UploadExcelFile(FileName, Bytes)                 ' Display the confirmation message.                 lblInfo.Text = FileName & " uploaded successfully."                 txtFile.Text = "" 

             Catch Err As System.Web.Services.Protocols.SoapException                 lblInfo.Text = "Server error: " & Err.Message             Catch Err As Exception                 lblInfo.Text = Err.Message             Finally                 If Not (fs Is Nothing) Then                     fs.Close()                 End If             End Try         End If     End Sub End Class