There are so many APIs that we cannot use directly. Some of them require an authorized Token first and then we can use that Token to Authenticate that API.

The following is sample code to authenticate an API:

Dim WebServiceURI As String = "API Url"

        Dim webrequestobj As HttpWebRequest = DirectCast(WebRequest.Create(WebServiceURI), HttpWebRequest)

        Dim soapAction = ""

        Dim WebServiceData As StringBuilder = New StringBuilder

        Dim WebServiceByteData As Byte() = Encoding.UTF8.GetBytes(WebServiceData.ToString)

        webrequestobj.Method = "GET"

        webrequestobj.ContentType = "application/json"

        webrequestobj.Credentials = CredentialCache.DefaultCredentials

        webrequestobj.Headers.Add(HttpRequestHeader.Authorization, "AuthoreizeToken")

        Try

            Using Response As HttpWebResponse = TryCast(webrequestobj.GetResponse(), HttpWebResponse)

                Dim reader As New StreamReader(Response.GetResponseStream())

                Dim str As String = reader.ReadLine()

            End Using

        Catch ex As Exception

        End Try