c#实现ajax通信：向后台发送JSON字符串，接收响应字符串，并转换为对象

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c#实现ajax通信，通过向服务器后台发送json数据，接收响应数据提交给前台。

其中包含两个主要函数，发送数据，接收响应数据的Http请求响应函数。另一个是将对象转化为JSON字符串的序列化函数。

需要下载并在引用空间中引入Newtonsoft.Json.dll，​​下载​​

using Newtonsoft.Json.Linq;
using Newtonsoft;
using Newtonsoft.Json;


/// <summary>
/// 向服务器后台发送json数据，需要引入Newtonsoft.Json.dll
/// </summary>
/// <param name="urlpath">请求地址</param>
/// <param name="diclist">json键值对</param>
/// <returns></returns>
public static JObject ajax(string urlpath, Dictionary<String, String> diclist)
{
    HttpWebRequest req = (HttpWebRequest)WebRequest.Create(urlpath);
    req.Method = "POST";
    req.ContentType = "application/x-www-form-urlencoded";

    //设置参数，并进行URL编码
    //虽然我们需要传递给服务器端的实际参数是JsonParas（格式：[{"UserID":"0206001","username","ceshi"}]）
    //但是需要将字符串参数构造成键值对的形式，注："paramaters=["userid":"206001","username","ceshi"}]"
    //其中键paramaters为webservice接口函数的参数名，值为经过序列化的Json数据字符串
    //最后将字符串参数进行url编码

    String poststr = buildQueryStr(diclist);
    byte[] payload = Encoding.UTF8.GetBytes(poststr);

    req.ContentLength = payload.Length;
    //发送请求，获得请求流
    Stream writer;
    try
    {
        writer = req.GetRequestStream();   //获取用于写入请求数据的Stream对象
    }
    catch (Exception)
    {
        writer = null;
        MessageBox.Show("连接服务器失败");
        return null;
    }
    //将请求参数写入流
    writer.Write(payload, 0, payload.Length);
    writer.Close();  //关闭请求流

    string strvalue = "";   //srevalue为http响应所返回的字符流
    HttpWebResponse response;
    try
    {
        //获得响应流
        response = (HttpWebResponse)req.GetResponse();
    }
    catch (WebException ex)
    {
        response = ex.Response as HttpWebResponse;
    }
    Stream s = response.GetResponseStream();
    StreamReader reader = new StreamReader(s);
    strvalue = reader.ReadToEnd();
    reader.Close();
    s.Close();
    JObject JSONobj = JObject.Parse(strvalue);
    //lei.ziji = JsonConvert.DeserializeObject<user_me_back>(JSONobj["data".ToString()]);  //将字符串转化为类实例
    return JSONobj;
}




//将键值对序列转化为请求网址字符串
public static String buildQueryStr(Dictionary<String,String> diclist)
{
    Dictionary<string, string> dd = new Dictionary<string, string>();
    dd.Add("key1", "value1");
    string aa = dd["key1"];

    string poststr = "";
    foreach (var item in diclist)
    {
        poststr += item.Key + "=" + HttpUtility.UrlEncode(item.Value,Encoding.UTF8)+"&";
    }
    poststr = poststr.Substring(0, poststr.LastIndexOf("&"));
    return poststr;
}