C#調用HTTP POST請求上傳圖片

現在很多B/S系統的開發都是通過API方式來進行的，一般服務端會開放一個API接口，客戶端調用API接口來實現圖片或文件上傳的功能。

前段時間碰到需要使用POST請求上傳圖片的功能，好久沒寫了，重新整理下函數，方便后續使用。

為了使用的通用性，函數做了一定的封裝，具體代碼如下：

　　　　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"); // 隨機分隔線
            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);

            //請求頭部信息 
            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();
        }

使用起來也比較方便，調用方法如下：

UploadImage("圖上上傳接口地址","本地圖片文件路徑","接口提供的上傳參數名稱，沒有默認為file");

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