.Net Core WebAPI + Axios +Vue 實現下載與下載進度條

故事的開始

老闆說：系統很慢，下載半個小時無法下載，是否考慮先壓縮再給用戶下載？

　　本來是已經壓縮過了，不過第一反應應該是用戶下的數量多，導致壓縮包很大，然後自己測試發現，只是等待的時間比較久而已，仍然是下載狀態中，並不是系統慢，但是用戶體驗肯定是最直觀的，確實是我們做得不夠好，單純彈出遮罩層顯示冰冷的“拼命載入中……”，對用戶來說確實不夠友好。嗯，瞭解實際情況了，那就開擼，增加用戶體驗。

 解決它

效果圖：

Vue+ElementUI

 <el-progress v-if="dlProgress>0" :text-inside="true" :stroke-width="18" :percentage="dlProgress" status="success" style="margin-bottom:10px"></el-progress>

Axios

downloadTask(index,row) {
      let own =this;
      this.fullscreenLoading = true;
      this.axios({
        method: 'post',
        url: this.baseUrl + '/api/Task/DownLoad',
        data: {id: row.id},
        responseType: 'blob',
　　　　 //敲黑板
        onDownloadProgress (progress) {
          own.dlProgress=Math.round(progress.loaded / progress.total * 100);
        }
      })
      .then((res) => {
        this.fullscreenLoading = false;
        let fileName = decodeURI(res.headers["content-disposition"].split("=")[1]);
        let url = window.URL.createObjectURL(new Blob([res.data]));
        let link = document.createElement('a');
        link.style.display = 'none';
        link.href = url;
        link.setAttribute('download', fileName);
        document.body.appendChild(link)
        link.click()
        this.$message.success('下載成功');
      })
      .catch(() => {
        this.fullscreenLoading = false;
      });
    },

下載：

    public static class HttpContextExtension
    {
        /// <summary>
        /// 獲取客戶Ip
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        public static string GetClientUserIp(this HttpContext context)
        {
            var ip = "";
            if (context.Request.Headers.ContainsKey("X-Forwarded-For"))
            {
                ip = context.Request.Headers["X-Forwarded-For"].ToString();
            }
            if (string.IsNullOrEmpty(ip) && context.Request.Headers.ContainsKey("X-Real-IP"))
            {
                ip = context.Request.Headers["X-Real-IP"].ToString();
            }
            if (string.IsNullOrEmpty(ip))
            {
                ip = context.Connection.RemoteIpAddress.MapToIPv4().ToString();
            }
            if (string.IsNullOrEmpty(ip))
                return ip;
            var sp = ip.RemoveSpacing().Split(',');
            return sp[0];
        }

        /// <summary>
        /// 通過文件流下載文件
        /// </summary>
        /// <param name="context"></param>
        /// <param name="filePath">文件完整路徑</param>
        /// <param name="contentType">訪問這裡 https://tool.oschina.net/commons </param>
        public static void DownLoadFile(this HttpContext context,string filePath, string contentType= "application/octet-stream")
        {
            var fileName = Path.GetFileName(filePath);

            int bufferSize = 1024; 
            context.Response.ContentType = contentType;
            context.Response.Headers.Append("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(fileName));
            context.Response.Headers.Append("Charset", "utf-8");
            context.Response.Headers.Append("Access-Control-Expose-Headers", "Content-Disposition");
            //context.Response.Headers.Append("Access-Control-Allow-Origin", "*");
            //使用FileStream開始迴圈讀取要下載文件的內容
            using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
            {
                using (context.Response.Body) 
                {
                    long contentLength = fs.Length; 
                    context.Response.ContentLength = contentLength;

                    byte[] buffer;
                    long hasRead = 0;  
                    while (hasRead < contentLength)
                    {
                        if (context.RequestAborted.IsCancellationRequested)
                        {
                            break;
                        }

                        buffer = new byte[bufferSize];
                        //從下載文件中讀取bufferSize(1024位元組)大小的內容到伺服器記憶體中
                        int currentRead = fs.Read(buffer, 0, bufferSize);
                        context.Response.Body.Write(buffer, 0, currentRead);
                        context.Response.Body.Flush();
                        hasRead += currentRead;
                    }
                    context.Response.Body.Close();
                }
                fs.Close();
            }
        }

        /// <summary>
        /// 通過文件流下載文件
        /// </summary>
        /// <param name="context"></param>
        /// <param name="filePath">文件完整路徑</param>
        /// <param name="contentType">訪問這裡 https://tool.oschina.net/commons </param>
        public static void DownLoadFile(this HttpContext context,string fileName, byte[] fileByte, string contentType = "application/octet-stream")
        {
            int bufferSize = 1024;
            
            context.Response.ContentType = contentType;
            context.Response.Headers.Append("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(fileName));
            context.Response.Headers.Append("Charset", "utf-8");
            context.Response.Headers.Append("Access-Control-Expose-Headers", "Content-Disposition");
         
            //context.Response.Headers.Append("Access-Control-Allow-Origin", "*");
            //使用FileStream開始迴圈讀取要下載文件的內容
            using (Stream fs = new MemoryStream(fileByte))
            {
                using (context.Response.Body)
                {
                    long contentLength = fs.Length;
                    context.Response.ContentLength = contentLength;

                    byte[] buffer;
                    long hasRead = 0;
                    while (hasRead < contentLength)
                    {
                        if (context.RequestAborted.IsCancellationRequested)
                        {
                            break;
                        }
                        
                        buffer = new byte[bufferSize];
                        //從下載文件中讀取bufferSize(1024位元組)大小的內容到伺服器記憶體中
                        int currentRead = fs.Read(buffer, 0, bufferSize);
                        context.Response.Body.Write(buffer, 0, currentRead);
                        context.Response.Body.Flush();
                        hasRead += currentRead;
                    }
                }
            }
        }
    }

完美~