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ASP.NETFile Upload, Exception Handling

• David Turton
• Conestoga College
• Institute of Technology and Advanced Learning
• http//www.conestogac.on.ca/dturton
• Doon 1D17, x 3610

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Objectives

• File Upload
• Upload files to a server
• Exception Handling
• Create exceptions
• Use Try-Catch-Finally construct
• To intercept exceptions (abends)

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File Upload
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File Upload

• Allows users to upload a file to server
• Browse button included
• To select local file to be uploaded
• You control destination on server
• User presents a file
• you code target path filename
• Individual user rights are not relevant
• It's ASPNET user doing the writing

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Text box for name of file at server (or default
to source file name)
Button to enact upload
Could provide a text box to input the target
directory or just default it by application, user
name, etc.
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Uploading Files to NTFSwith IIS user ASPNET
needs permissions

• Windows Explorer
• Tools ? Options
• "View" tab
• Clear Use Simple File Sharing (Recommended)"
• Security tab becomes available
• Gives access to NTFS permissions
• Give user ASPNET modify rights
• In folder properties, Security tab

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Allow ASPNET user to change files
properties
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CCode to enact upload

• Private void btnUpload_Click(ByVal sender As
• try
• if (txtServerName.Text null
  txtServerName.Text.Trim() "")
• lblError.Text "Error need file-name for
  server"
• else
• String uploadDir Server.MapPath("/images")
  
• upldSource.PostedFile.SaveAs(uploadDir _at_"\"
  txtServerName.Text)
• catch (Exception ex)
• lblMessage.Text "exception
  thrown " ex.Message

Get actual path to the site-relative path/images
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VBCode to enact upload

• Protected Sub btnUpload_Click(ByVal sender As
• Try
• If (txtServerName.Text Is Nothing OrElse
  txtServerName.Text.Trim() "")
• lblError.Text "Error need file-name for
  server"
• else
• Dim uploadDir As string Server.MapPath("/i
  mages")
• upldSource.PostedFile.SaveAs(uploadDir "\"
  txtServerName.Text)
• End If
• Catch ex As Exception
• lblMessage.Text "exception thrown
  " ex.Message
• End Try

Get actual path to the site-relative path/images
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Server.MapPath("/images")

• Returns actual physical path on server
• Starting from the drive letter
• Parameter is assumed to be a relative address
• Based on 1st character
• / means relative to the web site
• All else assumed relative to current web page
• "/" or "\" as a 1st character is invalid
• Will double "\" between path parameter

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Properties of Interestassume browse control is
called "upldSource"

• upldSource.PostedFile.FileName
• Returns source file-name and path
• UpldSource.FileName
• Returns source file-name extension, no path
• upldSource.PostedFile.ContentLength
• Length of file being uploaded check for zero
  length
• upldSource.PostedFile.ContentType
• Type of file being uploaded, as general/specific
  pair image/jpg
• File extension not always indicative of file type
  (in Linux and UNIX)
• System.IO.Path.GetFileName(upldSource.PostedFile.F
  ileName)
• Returns input file-name extension (no path)
• System.IO.Path.GetFileExtension(upldSource.PostedF
  ile.FileName)
• Returns input file-name extension only
• System.IO.Path.GetDirectoryName(upldSource
  PostedFile.FileName)
• Returns input file's source path

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Exception Handling
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Exception Handling (simple)

• For commands likely to get an exception (abend)
• Put within a Try construct
• Use Catch construct to interpret the error
• Usually, just display the error text ex.Message
• Exceptions outside a Try-Catch construct
• Will abend program kick user off your site

try commands to upload file, modify
database, etc. things to do if it works
catch (Exception ex) lblMessage.Text
"Here is the exceptionltbr /gt"
ex.Message finally things to do
regardless
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Try Catch - Finally

• Commands in Try are executed in sequence
• On an exception (error)
• Processing jumps to Catch code
• Remaining Try code is discarded
• Exception or not
• Commands in Finally block are executed
• Code following Try-Catch-Finally is executed
• Unless Try or Catch execute a Return
• (or Throw an exception back to calling program)
• Even if the code says to leave the procedure,
  Finally is executed before it does so.
• If you have a blank Catch block
• You're hiding the abend and processing will
  continue
• You'll lose marks on assignments

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MultiView Wizard Controls
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New with ASP.NET 3.5MultiView Wizard Controls

• Draft a single form
• Divide it into sections
• Present one section at a time
• Fields on all sections
• Available at all times

• MultiView
• You control
• .ActiveViewIndex
• Navigation buttons
• Content of each section
• Wizard
• Generates
• Previous/Next/Finish buttons
• Navigation menu
• You control
• Content of each section

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Assigning buttons to same handlerCreate one or
two button handlers, rename them (PanelNext,
PanelBack)Assign pertinent handler to all Next
and Back buttons
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MultiView ControlView-to-view navigation code
// on initial load, display the first
panel protected void Page_Load(object sender,
EventArgs e) if (!IsPostBack)
viewSurvey.ActiveViewIndex 0 // all next
buttons just increment the view index protected
void PanelNext(object sender, EventArgs
e) viewSurvey.ActiveViewIndex // all back
buttons decrement the view index protected void
PanelBack(object sender, EventArgs
e) viewSurvey.ActiveViewIndex--
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Wizard ControlMultiple-template formsYou
provide content ? it provides navigation
You provide content on each panel, the wizard
provides menu on left Next/Prior buttons
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Added by wizard
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ltaspWizardStepgt attributes(some)

• Title"xxx"
• Title of step shown in hyperlink navigation
• AllowReturn"False"
• If true (default), users can come back to this
  step
• If false, users can't, but can jump over it
• StepType"xxx"
• "Auto" default
• "Start" only Next button
• "Step" Next Previous
• "Finish" only Finish button
• "Complete" doesn't appear in hyperlink menu

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Wizard Events

• Xxx_NextButtonClick
• Look at e.NextStepIndex
• Next step to be displayed
• Can use input fields to decide whether to jump
  this step or not

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Wizard Step event OnActivateuse to preload step
with data from other steps,decide whether to do
step, etc.