public static HttpRequestMessage AsHttpRequestMessage(this HttpRequestBase request) {
    Requires.NotNull(request,"request");

    var httpRequest = new HttpRequestMessage(new HttpMethod(request.HttpMethod), request.Url);
    foreach (string header in request.Headers) {
        httpRequest.Headers.Add(header, request.Headers.GetValues(header));
    }

    if (request.Form != null) {
        // Avoid a request message that will try to read the request stream twice for already parsed data.
        httpRequest.Content = new FormUrlEncodedContent(request.Form.AsKeyValuePairs());
    } else if (request.InputStream != null) {
        httpRequest.Content = new StreamContent(request.InputStream);
    }

    return httpRequest;
}

/// <summary>
/// Clones an <see cref="HttpWebRequest" /> in order to send it again.
/// </summary>
/// <param name="message">The message to set headers on.</param>
/// <param name="request">The request with headers to clone.</param>
internal static void CopyHeadersFrom(this HttpRequestMessage message, HttpRequestBase request) {
    Requires.NotNull(request,"request");
    Requires.NotNull(message,"message");

    foreach (string headerName in request.Headers) {
        string[] headerValues = request.Headers.GetValues(headerName);
        if (!message.Headers.TryAddWithoutValidation(headerName, headerValues)) {
            message.Content.Headers.TryAddWithoutValidation(headerName, headerValues);
        }
    }
}