Use UploadStringAsync
method:
WebClient webClient = new WebClient();
webClient.UploadStringCompleted += (s, e) =>
{
if (e.Error != null)
{
//handle your error here
}
else
{
//post was successful, so do what you need to do here
}
};
webClient.UploadStringAsync(new Uri(yourUri), UriKind.Absolute), "POST", yourParameters);