Deleting using ListView

drbingen · March 29th, 2011, 12:51 AM

Imar,

This book is great! I worked through it completely and am now going back and working through certain sections again, particularly concepts that I have never worked with before such as LINQ and the ListView control.

The Delete button, referenced on page 457, removes the item from the Picture table which is the source table for the web page. However, it does not remove the actual file from the virtual folder. Is there a way to do this within the ListView control? Also, how could an album be deleted? Of course, this would require removing the name from the PhotoAlbum, removing the associated data rows in the Picture table and removing the actual files from the virtual folder.

Below is my code that correctly removes an album. Is there another way to do this? As you can tell, I'm working in VB.NET

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim photoAlbumId As Integer = Convert.ToInt32(DropDownList1.SelectedValue)
Dim myDatabaseContext As New SpaethFamilyDataContext
Dim pics = From p In myDatabaseContext.Pictures _
Where p.PhotoAlbum.Id = photoAlbumId _
Select p
For Each selectedDetail As Picture In pics
System.IO.File.Delete(Server.MapPath(selectedDetai l.ImageUrl))
myDatabaseContext.Pictures.DeleteOnSubmit(selected Detail)
Next
myDatabaseContext.SubmitChanges()
Dim Albm = From p In myDatabaseContext.PhotoAlbums _
Where p.Id = photoAlbumId _
Select p
myDatabaseContext.PhotoAlbums.DeleteAllOnSubmit(Al bm)
myDatabaseContext.SubmitChanges()
End Sub
End Class

Imar · March 29th, 2011, 02:49 AM

Hi there,

Your code looks fine, although you can do it slightly more efficient by querying the Album and the Pictures in one fell swoop:

Code:

 
Dim photoAlbumId As Integer = Convert.ToInt32(DropDownList1.SelectedValue)
Using myDatabaseContext As New PlanetWroxDataContext
  Dim album As PhotoAlbum = (From p In myDatabaseContext.PhotoAlbums _
                     Where p.Id = photoAlbumId _
                      Select p).FirstOrDefault()
  If album IsNot Nothing Then
    For Each pic As Picture In album.Pictures
      System.IO.File.Delete(Server.MapPath(pic.ImageUrl))
      myDatabaseContext.Pictures.DeleteOnSubmit(pic)
    Next
  myDatabaseContext.PhotoAlbums.DeleteOnSubmit(album)
  myDatabaseContext.SubmitChanges()
  End If
End Using

I also introduced a Using statement to automatically clean up the PlanetWrox data context when you no longer need it.

You can delete files with the ListView using its ItemDeleting event. Inside that event, you can construct a DataContext, delete the picture from disk and save the changes. This article may help in understanding what to do: http://www.4guysfromrolla.com/articles/052709-1.aspx

Hope this helps.

Cheers,

Imar

drbingen · March 29th, 2011, 04:03 AM

Imar,

The code you provided makes perfect sense.

I didn't find any events on the ListView control. Should I be looking for a delete event on the LinqDataSource?

Thanks again.

Imar · March 29th, 2011, 04:11 AM

Click the control in Design View and then look at the Events tab of the Properties Grid. It should be there:

http://msdn.microsoft.com/en-us/libr...(v=VS.90).aspx

Cheers,

Imar