c# - 如何使用 Web api 和 Angular 从字节下载文件

Question

我使用下面的代码来下载文件。我已在 Web api 中成功分配了 bytearray。

    byte[] bytes = llResponse.FileContent;
    response.Content = new ByteArrayContent(bytes)

但最后我的浏览器控制台得到了以下响应

SyntaxError: Unexpected token � in JSON at position 0 at JSON.parse (<anonymous>) at XMLHttpRequest.onLoad (http://localhost:4200/vendor.js:36098:51) at ZoneDelegate.invokeTask (http://localhost:4200/polyfills.js:9462:31) at Object.onInvokeTask (http://localhost:4200/vendor.js:99246:33) at ZoneDelegate.invokeTask (http://localhost:4200/polyfills.js:9461:60) at Zone.runTask (http://localhost:4200/polyfills.js:9239:47) at ZoneTask.invokeTask [as invoke] (http://localhost:4200/polyfills.js:9536:34) at invokeTask (http://localhost:4200/polyfills.js:10674:14) at XMLHttpRequest.globalZoneAwareCallback (http://localhost:4200/polyfills.js:10711:21)
message: "Unexpected token � in JSON at position 0

我使用的完整代码如下

Angular

 this.appService.DownloadFile(this.filter).subscribe((data) => {  
                
                
                importedSaveAs(data, this.filter.FileName)  

            })



public DownloadFile(obj:liveLinkFilter): Observable<any> {
        var url = this.baseApiUrl + 'RadioLink/DownloadFile';
        var reqHeader = new HttpHeaders({ 'Content-Type': 'application/json' });
        return this.httpService.post(url, obj, { headers: reqHeader, withCredentials: true });
    }

Web Api 代码

[HttpPost]
        [Route("DownloadFile")]
        public HttpResponseMessage DownloadFile(LiveLinkDocumentBO obj)
        {
            HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK);
            LLAccessResponse llResponse;

            //GetFileType(lvlnkBo.FileName);
            LLService llservice = new LLService();
            
            llResponse = llservice.FetchDocument(Convert.ToInt32(obj.FileId), obj.LLUserName, obj.FileName);
            //Read the File into a Byte Array.  
            byte[] bytes = llResponse.FileContent;
            response.Content = new ByteArrayContent(bytes);
            //Set the Response Content Length.  
            response.Content.Headers.ContentLength = bytes.LongLength;
            //Set the Content Disposition Header Value and FileName.  
            response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
            response.Content.Headers.ContentDisposition.FileName = obj.FileName;
            //Set the File Content Type.  
            response.Content.Headers.ContentType = new MediaTypeHeaderValue(MimeMapping.GetMimeMapping(obj.FileName));
            return response;
        }

Answer 1

Angular 的 HttpClient 默认假定响应是 JSON。如果 API 的响应是文本字符串，请将 HTTP 请求选项的 responseType 属性(httpService.post 的第三个参数)设置为 “text” 。如果响应是二进制数据，请将响应类型设置为 "arraybuffer" 或 "blob"。