How to take values from a web page in VB.NET

Greetings, Tutee.

The technique you're looking for is called HTML Parsing , which allows you to get the elements of any web page in the HTML DOM model.

On the internet you find some parser , however I was testing (since my strength is not vb.net) without downloading anything and the way it worked was using a WebBrowser (no need to add it to the form ).

This is the code, in the end I will explain some details:

Public Class Form1

    Dim web As WebBrowser  'Aquí se declara el WebBrowser

    Private Sub cargarPagina()
        web = New WebBrowser() ' Se instancia el WebBrower
        web.ScriptErrorsSuppressed = True ' Oculta la ventana de errores si algún script de la página falló (de todas formas no los necesitamos)
        web.Navigate(New Uri("https://www.precio-dolar.com.ar/")) ' Carga la página web creando un nuevo documento HTML

        ' Este Handler permite continuar con el proceso una vez que se ha cargado TODA la página (ya que si no ha cargado lanzará un error)
        AddHandler web.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf cargarValorDolar)
    End Sub

    Private Sub cargarValorDolar()

        If (web.Document IsNot Nothing) Then ' En caso de que la página no halla cargado bien el documento
            Dim divs = web.Document.Body.GetElementsByTagName("div") ' Obtiene todos los elementos <div> de la página web

            For Each div As HtmlElement In divs ' Recorre la lista de elementos <div>
                Dim className As String = div.GetAttribute("className") ' Obtiene el atributo [class] (nos servirá de filtro)
                If className = "currency-field-result" Then ' El texto con el que se compara es el que muestra el valor del dólar en pesos argentinos
                    Label1.Text = div.InnerText ' Se obtiene el valor del dólar

                End If
            Next
        End If
    End Sub

End Class

Basically, what is done is a search 'filter' between all <div> elements found on that web page by means of className which corresponds to: "currency-field-result" .

Here I leave the result:

The disadvantage of doing it this way is that it could vary according to the web page, you would have to manually modify the way you will 'filter' the results.

You could use a webservice of the ones in the network, HERE you have an article talking about it, maybe it's the simplest and most reliable option.

But as I see that you use .NET you can also do it by downloading the HTML code of the page that you indicate through its URL and reading the text value locating the tag that has the value (that is concretely a div that has this class "currency" -field-result "). The only problem with this is that they change the HTML code of the page ..

HERE you have an example of how to download an HTML page from your URL

I hope it serves you