GET

//直接返回字符串
public static string Gets(string url, JObject headers)
{
    string result = "";
    HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
    req.Method = "Get";
    if (headers != null)
    {
        IEnumerable<JProperty> properties = headers.Properties();
        foreach (JProperty item in properties)
        {
            req.Headers.Add(item.Name, item.Value.ToString());
        }
    }
    try
    {
        HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
        Stream stream = resp.GetResponseStream();
        //获取内容
        using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
        {
            result = reader.ReadToEnd();
        }
    }
    catch (Exception ex)
    {
        result = ex.Message;
    }
    return result;
}

// 直接读取文件流
public static string HttpGet(string url)
{
    HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
    req.Method = "Get";
    try
    {
        using (WebResponse wr = req.GetResponse())
        {
            HttpWebResponse response = wr as HttpWebResponse;
            Stream stream = response.GetResponseStream();
            //读取到内存
            MemoryStream ms = new MemoryStream();
            byte[] buffer = new byte[1024];
            while (true)
            {
                int sz = stream.Read(buffer, 0, 1024);
                if (sz == 0) break;
                ms.Write(buffer, 0, sz);
            }
            string content = Convert.ToBase64String(ms.ToArray());
            return content;
        }
    }
    catch (Exception ex)
    {
        return null;
    }
}

POST

application/json

public static string PostWebRequest(string postUrl, string paramData, int? timeOut)
{
    string responseContent = string.Empty;
    try
    {
        byte[] byteArray = Encoding.UTF8.GetBytes(paramData); //转化
        HttpWebRequest webReq = (HttpWebRequest)WebRequest.Create(new Uri(postUrl));
        webReq.Method = "POST";
        //这里的格式根据自己需求替换
        webReq.ContentType = "application/json";
        webReq.ContentLength = byteArray.Length;
        if(timeOut != null) webReq.Timeout = (int)timeOut;
        using (Stream reqStream = webReq.GetRequestStream())
        {
            reqStream.Write(byteArray, 0, byteArray.Length);//写入参数
            //reqStream.Close();
        }
        using (HttpWebResponse response = (HttpWebResponse)webReq.GetResponse())
        {
            //在这里对接收到的页面内容进行处理
            using (StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
            {
                responseContent = sr.ReadToEnd().ToString();
            }
        }
    }
    catch (Exception ex)
    {
        return ex.Message;
    }
    return responseContent;
}

application/x-www-form-urlencoded

public static string PostUrlFormUrlencoded(string url, string postData)
{
    string result = "";
    try
    {
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);

        req.Method = "POST";

        req.ContentType = "application/x-www-form-urlencoded";

        //req.Timeout = 8000;//请求超时时间

        byte[] data = Encoding.UTF8.GetBytes(postData);

        req.ContentLength = data.Length;

        using (Stream reqStream = req.GetRequestStream())
        {
            reqStream.Write(data, 0, data.Length);

            reqStream.Close();
        }

        HttpWebResponse resp = (HttpWebResponse)req.GetResponse();

        Stream stream = resp.GetResponseStream();

        //获取响应内容
        using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
        {
            result = reader.ReadToEnd();
        }
    }
    catch (Exception e)
    {
        Console.WriteLine("发送请求出错：" + e.Message);
    }

    return result;
}

multipart/form-data

public static string HttpPost(string url, NameValueCollection kVDatas = null, JObject headers = null,
    string method = WebRequestMethods.Http.Post, int timeOut = -1)
{
    try
    {
        string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
        byte[] boundarybytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
        byte[] endbytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.ContentType = "multipart/form-data; boundary=" + boundary;
        request.Method = "POST";
        request.KeepAlive = true;
        request.Timeout = timeOut;
        if (headers != null)
        {
            IEnumerable<JProperty> properties = headers.Properties();
            foreach (JProperty item in properties)
            {
                request.Headers.Add(item.Name, item.Value.ToString());
            }
        }

        CredentialCache credentialCache = new CredentialCache
        {
            { new Uri(url), "Basic", new NetworkCredential("member", "secret") }
        };
        request.Credentials = credentialCache;

        request.ServicePoint.Expect100Continue = false;
        using (Stream stream = request.GetRequestStream())
        {
            string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
            if (kVDatas != null)
            {
                foreach (string key in kVDatas.Keys)
                {
                    stream.Write(boundarybytes, 0, boundarybytes.Length);
                    string formitem = string.Format(formdataTemplate, key, kVDatas[key]);
                    byte[] formitembytes = Encoding.GetEncoding("UTF-8").GetBytes(formitem);
                    stream.Write(formitembytes, 0, formitembytes.Length);
                }
            }
            stream.Write(endbytes, 0, endbytes.Length);
        }
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        using (StreamReader stream = new StreamReader(response.GetResponseStream()))
        {
            return stream.ReadToEnd();
        }

    }
    catch (Exception e)
    {

        Console.WriteLine(e.Message);
        return e.Message;
    }
}

使用text形式发送multipart/form-data请求

JObject signatory = new JObject()
{
  { "content", "test content" }
};  
string boundary = "---------------------------" + timeStamp;
StringBuilder inStr = new StringBuilder();

inStr.Append("--" + timeStamp + "\r\n");
string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
string formitem = string.Format(formdataTemplate, "dataString", signData["content"]);
inStr.Append(formitem);
inStr.Append("\r\n" + "--" + timeStamp + "\r\n");
formitem = string.Format(formdataTemplate, "signatory", JsonConvert.SerializeObject(signatory));
inStr.Append(formitem);
inStr.Append("\r\n" + "--" + timeStamp + "\r\n");
formitem = string.Format(formdataTemplate, "tenantType", "PERSONAL");
inStr.Append(formitem);
inStr.Append("\r\n" + "--" + timeStamp + "\r\n");
inStr.Append("\r\n" + "--" + timeStamp + "--\r\n");

上传文件

public static string HttpUploadFile(string url, string filePath, string fileName, string paramName, string contentType,
    NameValueCollection nameValueCollection)
{
    string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
    byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    request.ContentType = "multipart/form-data; boundary=" + boundary;
    request.Method = "POST";
    request.KeepAlive = true;
    request.Credentials = CredentialCache.DefaultCredentials;
    Stream requestStream = request.GetRequestStream();
    string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
    foreach (string key in nameValueCollection.Keys)
    {
        requestStream.Write(boundarybytes, 0, boundarybytes.Length);
        string formitem = string.Format(formdataTemplate, key, nameValueCollection[key]);
        byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
        requestStream.Write(formitembytes, 0, formitembytes.Length);
    }
    requestStream.Write(boundarybytes, 0, boundarybytes.Length);
    string header = string.Format("Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n", paramName, fileName, contentType);
    byte[] headerbytes = Encoding.UTF8.GetBytes(header);
    requestStream.Write(headerbytes, 0, headerbytes.Length);
    FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
    byte[] buffer = new byte[4096];
    int bytesRead = 0;
    while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
    {
        requestStream.Write(buffer, 0, bytesRead);
    }
    fileStream.Close();
    byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
    requestStream.Write(trailer, 0, trailer.Length);
    requestStream.Close();
    WebResponse webResponse = null;
    try
    {
        webResponse = request.GetResponse();
        Stream responseStream = webResponse.GetResponseStream();
        StreamReader streamReader = new StreamReader(responseStream);
        string result = streamReader.ReadToEnd();
        return result;
    }
    catch (Exception ex)
    {
        if (webResponse != null)
        {
            webResponse.Close();
            webResponse = null;
        }
        return null;
    }
    finally
    {
        request = null;
    }
}