Asp.Net Core下HttpResponseMessage输出文件前端始终输出Json

我会带着你远行 2023-02-22 10:51 12阅读 0赞

今天有个场景需要webapi返回给客户端回应一个图片，以前的老套路不能用了。刚开始以为是需要使用“HttpResponseMessage“，直接使用HttpResponseMessage输出文件流

[HttpGet]
    [Route("get")]
    public HttpResponseMessage Get()
    {
        string path = @"C:\Users\***\Desktop\img0a28a1cbc674acd370585883abba3172.jpg";
        HttpResponseMessage message = new HttpResponseMessage(HttpStatusCode.OK);
        var bytes = GetIMGbyte(path);
        message.Content = new ByteArrayContent(bytes);
        message.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpg");
        message.Content.Headers.ContentLength = bytes.Length;
        return message;
    }

当我在浏览器中调用此终结点时，.Net Core 下 Web API会将`HttpResponseMessage的`HTTP内容标头设置为，以JSON形式返回`application/json`。

### 原因分析： ###

在[dnx][]或者是asp.net core的webapi里面，如果要返回一个图片，需要返回一个IActionResult类型的，因为这两个的框架把HttpResponseMessage 当成一个model来处理的，所以使用HttpResponseMessage 始终返回Json

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzI3NTU5MzMx_size_16_color_FFFFFF_t_70][]

{
      "version":{
        "major":1,"minor":1,"build":-1,"revision":-1,"majorRevision":-1,"minorRevision":-1
      },
      "content":{
        "headers":[
          {"Key":"Content-Type","Value":["image/jpg"]},
          {"Key":"Content-Length","Value":["206371"]}
        ]
      },
      "statusCode":200,"reasonPhrase":"OK","headers":[],"trailingHeaders":[],"requestMessage":null,"isSuccessStatusCode":true
    }

### 解决办法： ###

您可以使用以下方法返回FileResult：

1：返回FileContentResult

[HttpGet]
    [Route("get2")]
    public async Task<FileContentResult> GetFiel()
    {
        string path = @"C:\Users\admin\Desktop\hk\img0a28a1cbc674acd370585883abba3172.jpg";
        var mimeType = "image/jpg";
        var bytes = GetIMGbyte(path);
        return new FileContentResult(bytes, mimeType){
            FileDownloadName = "1.jpg"
            //如果设置了FileDownloadName ，则浏览器会直接下载该文件,不设置则浏览器会直接显示图片
        };
    }
    private byte[] GetIMGbyte(string PicturePath)
    {
        //将需要存储的图片读取为数据流
        FileStream fs = new FileStream(PicturePath, FileMode.Open, FileAccess.Read);           
        Byte[] btye2 = new byte[fs.Length];
        fs.Read(btye2, 0, Convert.ToInt32(fs.Length));
        fs.Close();
        return btye2;
    }

2：返回FileStreamResult

[HttpGet]
    [Route("get3")]
    public async Task<FileStreamResult> GetFiel3()
    {
        string path = @"C:\Users\admin\Desktop\hk\img0a28a1cbc674acd370585883abba3172.jpg";
        var stream = new FileStream(path, FileMode.Open);
        var mimeType = "image/jpg";          
        return new FileStreamResult(stream, mimeType) {
            FileDownloadName = "1.jpg"
            //如果设置了FileDownloadName ，则浏览器会直接下载该文件,不设置则浏览器会直接显示图片
        };
    }

参考资料：[Return file in ASP.Net Core Web API][]

[dnx]: https://docs.microsoft.com/en-us/dotnet/core/migration/from-dnx
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzI3NTU5MzMx_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200703002753148.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzI3NTU5MzMx,size_16,color_FFFFFF,t_70
[Return file in ASP.Net Core Web API]: https://stackoverflow.com/questions/42460198/return-file-in-asp-net-core-web-api