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Read Barcode From URL Asynchronously - VB.NET

Barcode Reader sample in VB.NET demonstrating ‘Read Barcode From URL Asynchronously’

Module1.vb
Imports System.IO
Imports System.Net
Imports System.Threading
Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq

' Cloud API asynchronous "Barcode Reader" job example.
' Allows to avoid timeout errors when processing huge or scanned PDF documents.

Module Module1

	' The authentication key (API Key).
	' Get your own by registering at https://app.pdf.co
	Const API_KEY As String = "***********************************"

	' Direct URL of source file to search barcodes in.
    ' You can also upload your own file into PDF.co and use it as url. Check "Upload File" samples for code snippets: https://github.com/bytescout/pdf-co-api-samples/tree/master/File%20Upload/   
	Const SourceFileURL As String = "https://bytescout-com.s3.amazonaws.com/files/demo-files/cloud-api/barcode-reader/sample.pdf"
	' Comma-separated list of barcode types to search. 
	' See valid barcode types in the documentation https://apidocs.pdf.co
	Const BarcodeTypes As String = "Code128,Code39,Interleaved2of5,EAN13"
	' Comma-separated list of page indices (or ranges) to process. Leave empty for all pages. Example: '0,2-5,7-'.
	Const Pages As String = ""
	' (!) Make asynchronous job
	Const Async As Boolean = True
	

	Sub Main()

		' Create standard .NET web client instance
		Dim webClient As WebClient = New WebClient()

		' Set API Key
		webClient.Headers.Add("x-api-key", API_KEY)

        ' Set JSON content type
        webClient.Headers.Add("Content-Type", "application/json")

		' Prepare URL for `Barcode Reader` API call
		Dim url As String = "https://api.pdf.co/v1/barcode/read/from/url"

        ' Prepare requests params as JSON
        ' See documentation: https : //apidocs.pdf.co
        Dim parameters As New Dictionary(Of String, Object)
		parameters.Add("types", BarcodeTypes)
		parameters.Add("pages", Pages)
		parameters.Add("url", SourceFileURL)
		parameters.Add("async", Async)

        ' Convert dictionary of params to JSON
        Dim jsonPayload As String = JsonConvert.SerializeObject(parameters)

		Try
			' Execute POST request with JSON payload
			Dim response As String = webClient.UploadString(url, jsonPayload)

			' Parse JSON response
			Dim json As JObject = JObject.Parse(response)

			If json("error").ToObject(Of Boolean) = False Then
				
				' Asynchronous job ID
				Dim jobId As String = json("jobId").ToString()
				' URL of generated JSON file with decoded barcodes that will available after the job completion
				Dim resultFileUrl As String = json("url").ToString()

				' Check the job status in a loop. 
				' If you don't want to pause the main thread you can rework the code 
				' to use a separate thread for the status checking and completion.
				Do
					Dim status As String = CheckJobStatus(jobId) ' Possible statuses: "working", "failed", "aborted", "success".

					' Display timestamp and status (for demo purposes)
					Console.WriteLine(DateTime.Now.ToLongTimeString() + ": " + status)

					If status = "success" Then
						
						' Download generated JSON results file as string
						Dim jsonFileString As String = webClient.DownloadString(resultFileUrl)

						Dim jsonFoundBarcodes As JArray = JArray.Parse(jsonFileString)

						' Display found barcodes in console
						For Each token As JToken In jsonFoundBarcodes
							Console.WriteLine("Found barcode:")
							Console.WriteLine("  Type: " + token("TypeName").ToString())
							Console.WriteLine("  Value: " + token("Value").ToString())
							Console.WriteLine("  Document Page Index: " + token("Page").ToString())
							Console.WriteLine("  Rectangle: " + token("Rect").ToString())
							Console.WriteLine("  Confidence: " + token("Confidence").ToString())
							Console.WriteLine()
						Next
						Exit Do

					ElseIf status = "working" Then

						' Pause for a few seconds
						Thread.Sleep(3000)

					Else

						Console.WriteLine(status)
						Exit Do

					End If

				Loop

			Else 
				Console.WriteLine(json("message").ToString())
			End If
			
		Catch ex As WebException
			Console.WriteLine(ex.ToString())
		End Try

		webClient.Dispose()


		Console.WriteLine()
		Console.WriteLine("Press any key...")
		Console.ReadKey()

	End Sub

	Function CheckJobStatus(jobId As String) As String

		Using webClient As WebClient = New WebClient()

			' Set API Key
			webClient.Headers.Add("x-api-key", API_KEY)
			
			Dim url As String = "https://api.pdf.co/v1/job/check?jobid=" + jobId

			Dim response As String = webClient.DownloadString(url)
			Dim json As JObject = JObject.Parse(response)

			return Convert.ToString(json("status"))

		End Using

	End Function

End Module

Resources.Designer.vb
'------------------------------------------------------------------------------
' <auto-generated>
'     This code was generated by a tool.
'     Runtime Version:4.0.30319.42000
'
'     Changes to this file may cause incorrect behavior and will be lost if
'     the code is regenerated.
' </auto-generated>
'------------------------------------------------------------------------------

Option Strict On
Option Explicit On


Namespace My.Resources

	'This class was auto-generated by the StronglyTypedResourceBuilder
	'class via a tool like ResGen or Visual Studio.
	'To add or remove a member, edit your .ResX file then rerun ResGen
	'with the /str option, or rebuild your VS project.
	'''<summary>
	'''  A strongly-typed resource class, for looking up localized strings, etc.
	'''</summary>
	<Global.System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "4.0.0.0"), _
	 Global.System.Diagnostics.DebuggerNonUserCodeAttribute(), _
	 Global.System.Runtime.CompilerServices.CompilerGeneratedAttribute(), _
	 Global.Microsoft.VisualBasic.HideModuleNameAttribute()> _
	Friend Module Resources

		Private resourceMan As Global.System.Resources.ResourceManager

		Private resourceCulture As Global.System.Globalization.CultureInfo

		'''<summary>
		'''  Returns the cached ResourceManager instance used by this class.
		'''</summary>
		<Global.System.ComponentModel.EditorBrowsableAttribute(Global.System.ComponentModel.EditorBrowsableState.Advanced)> _
		Friend ReadOnly Property ResourceManager() As Global.System.Resources.ResourceManager
			Get
				If Object.ReferenceEquals(resourceMan, Nothing) Then
					Dim temp As Global.System.Resources.ResourceManager = New Global.System.Resources.ResourceManager("ByteScoutWebApiExample.Resources", GetType(Resources).Assembly)
					resourceMan = temp
				End If
				Return resourceMan
			End Get
		End Property

		'''<summary>
		'''  Overrides the current thread's CurrentUICulture property for all
		'''  resource lookups using this strongly typed resource class.
		'''</summary>
		<Global.System.ComponentModel.EditorBrowsableAttribute(Global.System.ComponentModel.EditorBrowsableState.Advanced)> _
		Friend Property Culture() As Global.System.Globalization.CultureInfo
			Get
				Return resourceCulture
			End Get
			Set(ByVal value As Global.System.Globalization.CultureInfo)
				resourceCulture = value
			End Set
		End Property
	End Module
End Namespace

Settings.Designer.vb
'------------------------------------------------------------------------------
' <auto-generated>
'     This code was generated by a tool.
'     Runtime Version:4.0.30319.42000
'
'     Changes to this file may cause incorrect behavior and will be lost if
'     the code is regenerated.
' </auto-generated>
'------------------------------------------------------------------------------

Option Strict On
Option Explicit On


Namespace My

	<Global.System.Runtime.CompilerServices.CompilerGeneratedAttribute(), _
	 Global.System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.VisualStudio.Editors.SettingsDesigner.SettingsSingleFileGenerator", "11.0.0.0"), _
	 Global.System.ComponentModel.EditorBrowsableAttribute(Global.System.ComponentModel.EditorBrowsableState.Advanced)> _
	Partial Friend NotInheritable Class MySettings
		Inherits Global.System.Configuration.ApplicationSettingsBase

		Private Shared defaultInstance As MySettings = CType(Global.System.Configuration.ApplicationSettingsBase.Synchronized(New MySettings), MySettings)

#Region "My.Settings Auto-Save Functionality"
#If _MyType = "WindowsForms" Then
        Private Shared addedHandler As Boolean

        Private Shared addedHandlerLockObject As New Object

        <Global.System.Diagnostics.DebuggerNonUserCodeAttribute(), Global.System.ComponentModel.EditorBrowsableAttribute(Global.System.ComponentModel.EditorBrowsableState.Advanced)> _
        Private Shared Sub AutoSaveSettings(ByVal sender As Global.System.Object, ByVal e As Global.System.EventArgs)
            If My.Application.SaveMySettingsOnExit Then
                My.Settings.Save()
            End If
        End Sub
#End If
#End Region

		Public Shared ReadOnly Property [Default]() As MySettings
			Get

#If _MyType = "WindowsForms" Then
                   If Not addedHandler Then
                        SyncLock addedHandlerLockObject
                            If Not addedHandler Then
                                AddHandler My.Application.Shutdown, AddressOf AutoSaveSettings
                                addedHandler = True
                            End If
                        End SyncLock
                    End If
#End If
				Return defaultInstance
			End Get
		End Property
	End Class
End Namespace

Namespace My

	<Global.Microsoft.VisualBasic.HideModuleNameAttribute(), _
	 Global.System.Diagnostics.DebuggerNonUserCodeAttribute(), _
	 Global.System.Runtime.CompilerServices.CompilerGeneratedAttribute()> _
	Friend Module MySettingsProperty

		<Global.System.ComponentModel.Design.HelpKeywordAttribute("My.Settings")> _
		Friend ReadOnly Property Settings() As Global.ByteScoutWebApiExample.My.MySettings
			Get
				Return Global.ByteScoutWebApiExample.My.MySettings.Default
			End Get
		End Property
	End Module
End Namespace

PDF.co Web API: the Web API with a set of tools for documents manipulation, data conversion, data extraction, splitting and merging of documents. Includes image recognition, built-in OCR, barcode generation and barcode decoders to decode bar codes from scans, pictures and pdf.

Get your PDF.co API key here!

Download Source Code (.zip)

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