[内容类型更改后，API控制器不断返回JSON

Question

我正在编写API控制器，并试图使其返回jpg文件。但是，即使内容类型设置为“ application / jpg”，我的响应消息仍在继续返回json。

    public HttpResponseMessage Get()
    {

        var path = @"C:\Temp\Sample\background.jpg";

        var result = new HttpResponseMessage(HttpStatusCode.OK);
        var stream = new FileStream(path, FileMode.Open);
        result.Content = new StreamContent(stream);
        result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/jpg");
        result.Content.Headers.ContentType.MediaType = "application/jpg";
        result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
        {
            FileName = "background.jpg"
        };
        stream.Close();
        return result;
    }

调用控制器后，它返回的是：

{
    "version": {
        "major": 1,
        "minor": 1,
        "build": -1,
        "revision": -1,
        "majorRevision": -1,
        "minorRevision": -1
    },
    "content": {
        "headers": [
            {
                "Key": "Content-Type",
                "Value": [
                    "application/jpg"
                ]
            },
            {
                "Key": "Content-Disposition",
                "Value": [
                    "attachment; filename=background.jpg"
                ]
            }
        ]
    },
    "statusCode": 200,
    "reasonPhrase": "OK",
    "headers": [],
    "trailingHeaders": [],
    "requestMessage": null,
    "isSuccessStatusCode": true
}

Answer 1

当调用Web API时，响应将始终为JSON（这就是HttpResponseMessages的工作方式）。如果要通过API发送图像，则两种最简单的方法是发送指向图像的链接（如果托管图像），或者首先将图像转换为字节数组，如下所示：

 public HttpResponseMessage Get()
{

    var path = @"C:\Temp\Sample\background.jpg";

    var result = new HttpResponseMessage(HttpStatusCode.OK);
    using(var stream = new FileStream(path, FileMode.Open)){        
        var image = Image.FromStream(stream);
        result.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg");
        var memoryStream = new MemoryStream();
        image.Save(memoryStream, ImageFormat.Jpeg);
        result.Content = new ByteArrayContent(memoryStream.ToArray());
    }

    return result;
}

然后在您的客户端上，您可以使用类似以下的内容：

using (var memoryStream = new MemoryStream(YourReceivedByteArray))
{
     return Image.FromStream(memoryStream);
}