How to set proxy in webkit cairo.net?

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VB

Hi everybody,
I have webkit cairo web browser in my application which i use to connect to internet
using proxy and for that i use these two codes which didn't give me any result :

Imports System.Collections.Generic
Imports System.IO
Imports System.Net
Module ProxyMd

    Class simplehttp
        Public Function geturl(url As String, proxyip As String, port As Integer, proxylogin As String, proxypassword As String) As String
            Dim resp As HttpWebResponse
            Dim req As HttpWebRequest = DirectCast(WebRequest.Create(url), HttpWebRequest)
            req.UserAgent = "Mozilla/5.0″"
            req.AllowAutoRedirect = True
            req.ReadWriteTimeout = 5000
            req.CookieContainer = New CookieContainer()
            req.Referer = ""
            req.Headers.[Set]("Accept-Language", "en,en-us")
            Dim stream_in As StreamReader

            Dim proxy As New WebProxy(proxyip, port)
            'if proxylogin is an empty string then don’t use proxy credentials (open proxy)
            If proxylogin = "" Then
                proxy.Credentials = New NetworkCredential(proxylogin, proxypassword)
            End If
            req.Proxy = proxy

            Dim response As String = ""
            Try
                resp = DirectCast(req.GetResponse(), HttpWebResponse)
                stream_in = New StreamReader(resp.GetResponseStream())
                response = stream_in.ReadToEnd()
                stream_in.Close()
            Catch ex As Exception
            End Try
            Return response
        End Function

        Public Function getposturl(url As String, postdata As String, proxyip As String, port As Short, proxylogin As String, proxypassword As String) As String
            Dim resp As HttpWebResponse
            Dim req As HttpWebRequest = DirectCast(WebRequest.Create(url), HttpWebRequest)
            req.UserAgent = "Mozilla/5.0″"
            req.AllowAutoRedirect = True
            req.ReadWriteTimeout = 5000
            req.CookieContainer = New CookieContainer()
            req.Method = "POST"
            req.ContentType = "application/x-www-form-urlencoded"
            req.ContentLength = postdata.Length
            req.Referer = ""

            Dim proxy As New WebProxy(proxyip, port)
            'if proxylogin is an empty string then don’t use proxy credentials (open proxy)
            If proxylogin = "" Then
                proxy.Credentials = New NetworkCredential(proxylogin, proxypassword)
            End If
            req.Proxy = proxy

            Dim stream_out As New StreamWriter(req.GetRequestStream(), System.Text.Encoding.ASCII)
            stream_out.Write(postdata)
            stream_out.Close()
            Dim response As String = ""

            Try
                resp = DirectCast(req.GetResponse(), HttpWebResponse)
                Dim resStream As Stream = resp.GetResponseStream()
                Dim stream_in As New StreamReader(req.GetResponse().GetResponseStream())
                response = stream_in.ReadToEnd()
                stream_in.Close()
            Catch ex As Exception
            End Try
            Return response
        End Function
    End Class
End Module

another code:

#region "Using Proxy"
  <Runtime.InteropServices.DllImport("wininet.dll", SetLastError:=True)> _
    Private Shared Function InternetSetOption(ByVal hInternet As IntPtr, ByVal dwOption As Integer, ByVal lpBuffer As IntPtr, ByVal lpdwBufferLength As Integer) As Boolean
    End Function

    Public Structure Struct_INTERNET_PROXY_INFO
        Public dwAccessType As Integer
        Public proxy As IntPtr
        Public proxyBypass As IntPtr
    End Structure

    Private Sub UseProxy(ByVal strProxy As String)
        Const INTERNET_OPTION_PROXY As Integer = 38
        Const INTERNET_OPEN_TYPE_PROXY As Integer = 3

        Dim struct_IPI As Struct_INTERNET_PROXY_INFO

        struct_IPI.dwAccessType = INTERNET_OPEN_TYPE_PROXY
        struct_IPI.proxy = Marshal.StringToHGlobalAnsi(strProxy)
        struct_IPI.proxyBypass = Marshal.StringToHGlobalAnsi("local")

        Dim intptrStruct As IntPtr = Marshal.AllocCoTaskMem(Marshal.SizeOf(struct_IPI))

        Marshal.StructureToPtr(struct_IPI, intptrStruct, True)

        Dim iReturn As Boolean = InternetSetOption(IntPtr.Zero, INTERNET_OPTION_PROXY, intptrStruct, System.Runtime.InteropServices.Marshal.SizeOf(struct_IPI))
    End Sub
#end region 

Now i need to use webkit web browser execlusivly and i want to know how to set proxy settings in my browser.
Any help will be appreciated.