c# - HttpClient does not exist in .net 4.0: what can I do?

Question

Ok i edited my code i dont get errors but the messageBox.Show return nothing empty box. Maybe i need to add something in the referrer string ? I didnt understand what is the referrer and what should i put there. And i have a key already im using it in my code. The key is a long string and im using it in my code i dont use with the referrer. Why it dosent translate the word "hi" ?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Globalization;
using System.IO;
using System.Net;
using System.Web;
using System.Web.Script.Serialization;




namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        private JavaScriptSerializer _Serializer = new JavaScriptSerializer();

        public Form1()
        {
            InitializeComponent();
            string f = TranslateText("hi", "English", "German", "", "");
            MessageBox.Show(f);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
        }

        public string TranslateText(string inputText, string sourceLanguage, string destinationLanguage, string referrer, string apiKey)
        {
                string requestUrl = string.Format(
                    "http://ajax.googleapis.com/ajax/services/language/translate?v=1.0&q={0}&langpair={1}|{2}&key={3}", 
                    HttpUtility.UrlEncode(inputText), 
                    sourceLanguage.ToLowerInvariant(), 
                    destinationLanguage.ToLowerInvariant(), 
                    apiKey
                );

                try
                {
                    HttpWebRequest http = (HttpWebRequest)HttpWebRequest.Create(requestUrl);
                    http.Referer = referrer;
                    HttpWebResponse response = (HttpWebResponse)http.GetResponse();
                    using (StreamReader sr = new StreamReader(response.GetResponseStream()))
                    {
                        string responseJson = sr.ReadToEnd();
                        var translation = this._Serializer.Deserialize<Milkshake.Integration.Google.GoogleAjaxResponse<Milkshake.Integration.Google.Translate.TranslationResponse>>(responseJson);

                        if (translation != null && translation.ResponseData != null && translation.ResponseData.ResponseStatus == HttpStatusCode.OK)
                        {
                            return translation.ResponseData.TranslatedText;
                        }
                        else
                        {
                            return String.Empty;
                        }
                    }
                }
            catch
                {
                    return String.Empty;
            }
        }
    }
}

Answer 1

I've used HttpClient in .NET 4.0 applications on numerous occasions. If you are familiar with NuGet, you can do an Install-Package Microsoft.Net.Http to add it to your project. See the link below for further details.

http://nuget.org/packages/Microsoft.Net.Http