CODEWITHSUNDEEP
c#vb.net
Khan Engineer
Khan Engineer

Reputation: 408

Alternative Method for WebClient.OpenRead

As WebClient.OpenRead(url) is blocking main thread until it opens url, In my case when server is not responding then it blocks user from activity until it throws timeout exception that's why I need alternative code that should have time out or method that would get data asynchronously.

Here is my code

Public Function IsUpdateAvailable(ByVal isAutoUpdate As Boolean) As String
        Dim client As WebClient

        Try
            Dim configUrl As String = GetURL()
            Dim configFile As String = GetFileName()

            If String.IsNullOrEmpty(configUrl) Then
                If Not isAutoUpdate Then
                   Return "Unable to check for updates" 
                End If
            End If

            If String.IsNullOrEmpty(configFile) Then

                If Not isAutoUpdate Then
                    Return "Unable to check for updates" 
                End If

            End If

            configUrl = configUrl & configFile

            If Not configUrl.ToUpper.StartsWith("HTTP") Then
                configUrl = "http://" & configUrl
            End If
            client = New WebClient
            Dim gfStream As Stream = client.OpenRead(configUrl)
            Dim gfStreamReader As New StreamReader(gfStream)
            Dim line As String = String.Empty
            Dim version As String = String.Empty
            Dim stringList As New Collections.Generic.List(Of String)

            While Not gfStreamReader.EndOfStream
                line = gfStreamReader.ReadLine
                If Not String.IsNullOrEmpty(line) Then
                    stringList.Add(line)
                End If
            End While
            gfStreamReader.Close()
            gfStream.Close()

            If stringList.Count > 0 Then
                version = stringList(0)
                If stringList.Count > 1 Then
                    _downloadFilePath = stringList(1)
                End If
                If isGreaterVersion(version) Then
                    Return "True"
                Else
                    If Not isAutoUpdate Then
                        Return "Current version is up-to-date."
                    End If

                End If
            Else
                If Not isAutoUpdate Then
                   Return "Current version is up-to-date."
                End If
               Return False
            End If
        Catch ex As WebException
            Return "Unable to check for updates" 
        Catch ex As Exception
            Return "Unable to check for updates" ''
        End Try

    End Function

Upvotes: 0

Views: 1175

Answers (1)

Stephen McDowell
Stephen McDowell

Reputation: 959

WebClient has an Async version of OpenRead. OpenReadAsync.

Documenation: https://msdn.microsoft.com/en-us/library/system.net.webclient.openreadasync(v=vs.110).aspx

See Yuval's answer for an example: how to wait for webclient OpenReadAsync to complete

Upvotes: 1

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