C#调用HTTP POST请求上传图片

现在很多B/S系统的开发都是通过API方式来进行的，一般服务端会开放一个API接口，客户端调用API接口来实现图片或文件上传的功能。

前段时间碰到需要使用POST请求上传图片的功能，好久没写了，重新整理下函数，方便后续使用。

为了使用的通用性，函数做了一定的封装，具体代码如下：

　　　　public static void UploadImage(string uploadUrl,string imgPath,string fileparameter="file")
        {
            HttpWebRequest request = WebRequest.Create(uploadUrl) as HttpWebRequest;
            request.AllowAutoRedirect = true;
            request.Method = "POST";

            string boundary = DateTime.Now.Ticks.ToString("X"); // 随机分隔线
            request.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;
            byte[] itemBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "\r\n");
            byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");

            int pos = imgPath.LastIndexOf("/");
            string fileName = imgPath.Substring(pos + 1);

            //请求头部信息 
            StringBuilder sbHeader = new StringBuilder(string.Format("Content-Disposition:form-data;name=\""+fileparameter+"\";filename=\"{0}\"\r\nContent-Type:application/octet-stream\r\n\r\n", fileName));
            byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sbHeader.ToString());

            FileStream fs = new FileStream(imgPath, FileMode.Open, FileAccess.Read);
            byte[] bArr = new byte[fs.Length];
            fs.Read(bArr, 0, bArr.Length);
            fs.Close();

            Stream postStream = request.GetRequestStream();
            postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
            postStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
            postStream.Write(bArr, 0, bArr.Length);
            postStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
            postStream.Close();

            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            Stream instream = response.GetResponseStream();
            StreamReader sr = new StreamReader(instream, Encoding.UTF8);
            string content = sr.ReadToEnd();
        }

使用起来也比较方便，调用方法如下：

UploadImage("图上上传接口地址","本地图片文件路径","接口提供的上传参数名称，没有默认为file");

例如：UploadImage("http://xxx.com/upload","C:/test.jpg","upload");