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HTTP GET/POST using VB.NET and BackgroundWorker Class

August 9, 2012

A simple code example using VB.NET LAMDA’s to create an inline BackgroundWorker object. I’m not a VB guru so there may be better ways to do this.
MY REQUIREMENTS:

1. Inline (all started from a single CLICK event)
2. Async HTTPWebRequest
3. Populate ComboBox/Input with JSON formatted request results
4. VB.NET

Dim requestWorker As BackgroundWorker = New BackgroundWorker()

AddHandler requestWorker.DoWork, Sub(workerSender As Object, workerEvent As System.ComponentModel.DoWorkEventArgs)

Dim request As HttpWebRequest = CType(WebRequest.Create("http://www.contoso.com/somepage.html"), HttpWebRequest)

request.Method = "POST" ' Also "GET" allowed

' For POST operations request, not required for GET

Dim data As String = "var1=1&var2=2&var3=test"

request.ContentType = "application/x-www-form-urlencoded"

request.ContentLength = System.Text.Encoding.ASCII.GetBytes(data).Length

Dim requestStreamWriter As StreamWriter = New StreamWriter(request.GetRequestStream())

requestStreamWriter.Write(data)

requestStreamWriter.Flush()

requestStreamWriter.Close()

' End POST operation requirements

Dim response As String = New StreamReader(resourcesRequest.GetResponse().GetResponseStream(), System.Text.Encoding.UTF8).ReadToEnd()

Dim results As Dictionary(Of String, Object) = New Script.Serialization.JavaScriptSerializer().Deserialize(Of Dictionary(Of String, Object))(response)

' Do something with the results 
If results.ContainsKey("Response") Then

' Allows cross thread input manipulation
Me.Invoke(Sub(Items As Dictionary(Of String, Object))

Me.cmbMyList.Items.Clear()

For Each Item In results.Item("Response")

Me.cmbResource.Items.Add(Item.value)

Next

End Sub, results)

End If

End Sub

requestWorker.RunWorkerAsync()